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1
Abrahamsen, Ida Sinnes. "Wind tunnel model testing of offshore platforms." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18627.
Full textAbstract:
The purpose of this thesis is to highlight some of the areas of interest when it comes to wind tunnel experimenting of offshore platforms regarding stability concerns such as critical angles and wind overturning moment. Some important factors include design of tower geometry, the effect of surface roughness on drag, methods of calculating blockage corrections of wall interference and the generation of an atmospheric boundary layer to resemble full-scale conditions. Data obtained from wind tunnel experiments with two different models have been compared and discussed according to the areas of interest as mentioned above. Testing of platforms was done at NTNU with a six-component balance, measuring forces of drag, side and lift and moment of pitch, roll and yaw with increments of 10° the whole 360° to account for wind coming from all directions. Two geometries were tested for the tower members, one with a circular cross-section which was smaller than scale and another with a square cross-section in correct scale. There was noticeable change in both global forces and moments. Blockage corrections caused by wall interference were researched from different sources and reviewed, and it was apparent that it is still an area with lots of uncertainty. Consensus was that and area ratio of maximum 0.10 should be abided in any case and that the simplified method of Pope is widely used. An atmospheric boundary layer was simulated at NTNU using trial-and-error and the validity of this was confirmed by comparing experimental data with theoretical data regarding the velocity profile, turbulence intensity and energy spectrum. For the experiments of surface roughness on an individual circular cylinder and the corresponding change in drag, a simple three-component balance was used. The cylinder represents the platform legs. Two types of surface roughness were tested, first a plain wooden surface and then with a layer of coarse sand applied to the whole surface. It was seen that the rougher surface provoked an earlier transition to a turbulent boundary layer, causing an earlier drop in drag which is a better fit to estimated full-scale characteristics.Finally, the element that contributes most to the inaccuracy of the experiments is shown to be the difficulty of geometric similarity. Further investigation is needed.
2
Danis, Reed. "Investigating Forward Flight Multirotor Wind Tunnel Testing in a 3-by 4-foot Wind Tunnel." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1909.
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Investigation of complex multirotor aerodynamic phenomena via wind tunnel experimentation is becoming extremely important with the rapid progress in advanced distributed propulsion VTOL concepts. Much of this experimentation is being performed in large, highly advanced tunnels. However, the proliferation of this class of vehicles extends to small aircraft used by small businesses, universities, and hobbyists without ready access to this level of test facility. Therefore, there is a need to investigate whether multirotor vehicles can be adequately tested in smaller wind tunnel facilities. A test rig for a 2.82-pound quadcopter was developed to perform powered testing in the Cal Poly Aerospace Department’s Low Speed Wind Tunnel, equipped with a 3-foot tall by 4-foot wide test section. The results were compared to data from similar tests performed in the U.S. Army 7-by 10-ft Wind Tunnel at NASA Ames. The two data sets did not show close agreement in absolute terms but demonstrated similar trends. Due to measurement uncertainties, the contribution of wind tunnel interference effects to this discrepancy in measurements was not able to be properly quantified, but is likely a major contributor. Flow visualization results demonstrated that tunnel interference effects can likely be minimized by testing at high tunnel speeds with the vehicle pitched 10-degrees or more downward. Suggestions towards avoiding the pitfalls inherent to multirotor wind tunnel testing are provided. Additionally, a modified form of the conventional lift-to-drag ratio is presented as a metric of electric multirotor aerodynamic efficiency.
3
Kayisoglu, Bengi. "Investigation Of Wind Effects On Tall Buildings Through Wind Tunnel Testing." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613324/index.pdf.
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In recent years, especially in the crowded city-centers where land prizes have become extremely high, tall buildings with more than 30 floors have started to be designed and constructed in Turkey. On the other hand, the technical improvements have provided the opportunity of design and construction of more slender structures which are influenced by the wind actions more. If the building is flexible, wind can interact with it so the wind induced oscillations can be significantly magnified. In order to analyze the response of such buildings under wind effects, wind tunnel tests are accepted to be the most powerful tool all over the world. In this study, a series of tests were performed in Ankara Wind Tunnel on a model building in the shape of a rectangular prism. For the similitude of flow conditions, passive devices were designed. The response of the model building was measured through a high frequency base balance which was designed specifically for this case study. Through the tests, the effects of turbulence intensity, vortex shedding and wind angle of attack on the response of the building were questioned. Finally, the results were compared with the results of various technical specifications about wind.
4
Sheng, Wanan. "CFD simulations in support of wind tunnel testing." Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/5393/.
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CFD and wind tunnel simulations are complementary due to their inherent limitations. Wind tunnel tests apply to any hypothesis, but are limited by the tunnel wall interference/blockage, the model details, and even the distortion of the model. CFD are not limited in any of these ways, but limited in speed and memory and the lack of determinate set of equations. Theoretically, CFD can provide an assessment of any problem in fluid dynamics (Direct Numerical Simulation), but the requirements of speed and memory are far from being met presently, or even in the foreseeable future. Of necessity, present CFD applications, however, employ a turbulence model, which limits its application due to the problems in accuracy and reliability. Given the power of CFD however, the work contained herein makes use of the advantages of CFD and also the wind tunnel, to form a powerful facility for aerodynamic test, i.e., CFD was used to complement and enhance the wind tunnel test, so producing an integrated test facility. A very important aspect in this work is that CFD was used to investigate the blockage correction for wind tunnel tests. By using CFD, the blockage correction could be made directly, in terms of representing the test model and tunnel walls in high fidelity. Meanwhile, the effect of support system on the test model was also investigated by CFD. The numerical results showed significant effect of the strut on the test model in the Argyll Wind Tunnel (Glasgow University), and an interesting result showed that different positions of support system had different effects. This research aimed to utilise CFD to support wind tunnel testing, and its ultimate purpose is to form a powerful facility for aerodynamic test by combining CFD and wind tunnel. The contributions are summarised as follows: The calibrations of wind tunnel by CFD simulations; A proposed improvement for moving belt system by CFD tools; Blockage correction of wind tunnel by CFD method; and The confirmation of CFD results by wind tunnel model test.
5
Abudaram, Yaakov Jack. "Wind tunnel testing of load-alleviating membrane wings." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041340.
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Hameury, Michel. "Development of the tolerant wind tunnel for bluff body testing." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27311.
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In conventional wind tunnels the solid-wall or open-jet test section imposes on the flow field around the test model new boundary conditions absent in free air. Unless a small model is used, the solid-wall test section generally increases the loadings on the model while the open-jet boundary decreases the loadings compared to the unconfined case.
However, the development of a low wall-interference test section and its successful demonstration would allow the testing of relatively large models without the application of often uncertain correction formulae.
The Tolerant wind tunnel, which makes use of the opposite effects of solid and open boundaries, is a transversely slatted-wall test section designed to produce at an optimal wall open-area ratio (OAR) low-correction data for a wide variety of model shapes and sizes. Initially intended for low-speed airfoil testing, its use is theoretically and experimentally investigated here in connection with bluff body testing.
A simple mathematical model based on two-dimensional potential flow theory and solved with the help of a vortex surface-singularity technique is used to estimate the best wall configuration. The theory predicts an optimum OAR of about 0.45 at which pressure distributions on flat plate and circular cylinder models of blockage ratios up to 33.3 % would differ from the free-air values by not more than 1 %.
On the other hand, experiments performed with flat plate, circular cylinder and circular-cylinder-with-splitter-plate models indicate the existence of an optimum configuration around OAR = 0.6. The experiments also show a maximum allowable blockage in the Tolerant wind tunnel to be equivalent to the blockage created by a 33.3 %-blockage-ratio flat plate model.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Kong, Lingzhe. "Experimental investigation of the tolerant wind tunnel for unsteady airfoil motion testing." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29992.
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Previously, the concept of the tolerant wind tunnel, developed in the Department of Mechanical Engineering, U. B. C., was tested only for stationary models. In the present study, the concept is investigated for unsteady airfoil motion. The new wind tunnel test section, using the opposite effects of solid and open boundaries, is a new approach to reduce wall blockage effects. Consisting of vertical airfoil slats uniformly spaced on both side walls in the test section, it is designed to produce a nearly free-air test environment for the test model, which leads to negligible or small corrections to the experimental results. The performance of this wind tunnel for unsteady model testing is examined experimentally
with a two-dimensional NACA 0015 airfoil in a simple plunging sinusoidal motion. The airfoil is mounted vertically in the center plane of the test section between solid ceiling and floor. An oscillating table is designed to give the airfoil an accurate plunging sinusoidal motion. A full range of open area ratio is tested by varying the number
of slats mounted inside the side walls. Pressure distribution along the airfoil surface and displacement of the airfoil are measured as functions of time by a data acquisition system designed for this research. Lift and moment are obtained by integration of the pressure distribution at every time increment.
Using a numerical model based on the singularity distribution method, the free air case results for a NACA 0015 airfoil in the same unsteady motion are obtained. Comparison with the linear theory results by Sears¹ are discussed. Comparing with the numerical and the linear theory results, the experimental investigation shows that the new test section produces low-correction data.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
8
Hetherington, Ben. "Interference of supports used for ground vehicle wind tunnel testing." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2671/.
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In order to provide a correct aerodynamic simulation of a vehicle travelling along the ground, models are tested using rotating wheels in a wind tunnel with a moving ground. In the most common of moving ground configurations the model is supported by an overhead strut, usually designed as an aerofoil profile to minimise interference, with the wheels supported by lateral stings hinged to mounts outside the span of the moving ground plane. ๒ using this type of configuration it is assumed that the presence of the intruding supports do not markedly affect the aerodynamic behaviour of the model, but this assumption is not always valid. In order to quantify interference effects from model supports, a range of models were tested over a stationary ground plane mounted to an under floor balance. Each model was tested with and without mock struts and stings, which do not actually support the model. Comparisons were made between configurations with and without the mock supports in order to quantify their aerodynamic effects and investigate any changes in flow structure. Force and moment measurements show significant effects on both drag (up to 25 counts / 7% of total drag) and lift (up to 170 counts) due to a vertical strut for all vehicle types. Motor Sport models, whose performance relies greatly on the underside flow, are largely affected (26 counts / 3% on drag and up to 250 counts on lift) by the presence of lateral stings. Passenger vehicle models with larger ride heights were not as sensitive to the use of stings. Further investigation into the flow mechanisms that create these effects were carried out in the form of pressure and velocity measurements in the model and support wakes, surface oil flow visualisations, and surface static pressure readings. Results showed that the strut wake impinged on the rear wings of the motor sport vehicle models and the backlight of the passenger vehicle models as expected, but its influence was more wide ranging than this, extending to the model under floor. To explore changes in flow structure local to the strut-model junction, the junction is simplified as an aerofoil intersecting a flat plate and modelled in Fluent. Comparisons were made between configurations with and without the presence of six different aerofoil profiles for four different boundary layer thicknesses. Results found a noticeable interference on the plate from the union of the aerofoil, but showed that when the magnitude of the interference effect was recalculated using model frontal area the portion of the interference local to the junction affecting the model was small and in some cases insignificant. It was determined that deficiencies in the wake of the supports and their complex interference flow fields were creating a much greater amount of the overall effect by interfering with vehicle features downstream. Due to the complexity of interactions between struts, stings, and the model, the effect of combining them for a common moving ground configuration was highly vehicle dependent, precluding the possibility of developing a reliable correction for interference effects. The results do, however, lead to suggestions for support-model coupling methods that minimise the magnitude of the effect and offer guidelines for the expected magnitudes of effects for the different vehicle types and struts tested.
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Lewis, Mark Charles. "Aerofoil testing in a self-streamlining flexible walled wind tunnel." Thesis, University of Southampton, 1987. https://eprints.soton.ac.uk/52285/.
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Ratliff, Card. "Revitalization and initial testing of a blowdown supersonic wind tunnel." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-07312008-093307.
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Joseph, Liselle AnnMarie. "Transition Detection for Low Speed Wind Tunnel Testing Using Infrared Thermography." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78145.
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Transition is an important phenomenon in large scale, commercial, wind tunnel testing at low speeds because it is an excellent indicator of an airfoil performance. It is difficult to estimate transition through numerical techniques because of the complex nature of viscous flow. Therefore experimental techniques can be essential. Over the transition region the rate of heat transfer shows significant increases which can be detected using infrared thermography. This technique has been used predominantly at high speeds, on small models made of insulated materials, and for short test runs. Large scale testing has not been widely undertaken because the high sensitivity of transition to external factors makes it difficult to detect.
The present study records the process undertaken to develop, implement and validate a transition detection system for continual use in the Virginia Tech Stability Wind Tunnel: a low speed, commercial wind tunnel where large, aluminium models are tested. The final system developed comprises of two high resolution FLIR A655sc infrared cameras; four 63.5-mm diameter circular windows; aluminium models covered in 0.8-mm silicone rubber insulation and a top layer of ConTact© paper; and a series of 25.4-mm wide rubber silicone fiberglass insulated heaters mounted inside the model and controlled externally by experimenters. This system produces images or videos of the model and the associated transition location, which is later extracted through image processing methods to give a final transition location in percentage chord.
The system was validated using two DU96-W-180 airfoils of different chord lengths in the Virginia Tech Stability Wind Tunnel, each tested two months apart. The system proved to be robust and efficient, while not affecting the airfoil performance or any other system in use in the wind tunnel. Transition results produced by the system were compared to measurements obtained from pressure data and stethoscope tests as well as the numerical predictions of XFOIL. The transition results from all four methods showed excellent agreement with each other for the two models, for at least two Reynolds numbers and for several angles of attack on both suction and pressure side of the model. The agreement of data obtained under such different conditions and at different times suggests that the infrared thermography system efficiently and accurately detects transition for large aluminium models at low speeds.Master of Science
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Garbutt, Keith Stuart. "Propulsion simulation in a magnetic suspension wind tunnel with special reference to force measurement." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336134.
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Malik, Abdullah. "Suppression of junction flow effects in half model wind tunnel testing." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/11568.
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Half model testing is considered a valuable wind tunnel technique that offers many benefits over conventional full span testing. The technique suffers from aerodynamic losses due to flow separations on the model surfaces near the model/floor junction. Computational Fluid Dynamics, employing the Spalart-Allmaras turbulence model, and experimental investigations were carried out to evaluate the losses and to investigate the effect of localised suction on the junction flows. The wind tunnel model used was a rectangular and untwisted wing having a NASA LS(1)-0413 cross section and with a physical aspect ratio of 3. Tests were conducted at 10.00 incidence at a Reynolds number of 0.44 x 106. Aerodynamic performance of the wind tunnel half model was obtained by surface flow visualisation and pressure measurements on the wing surface in the junction region. CFD predictions showed significantly large losses compared to the experimental findings and therefore CFD predicted significant influence and benefits of suction. These were seen as elimination of the model surface separation and also recovery of the wing surface pressure distributions. In contrast to this, experiments showed much smaller separation than CFD without suction and applying suction in experiments, showed only a marginal effect on the flow separations, which also further deteriorated the pressure distributions. Future CFD studies on junction flows should be conducted using more advanced turbulence models such as Large Eddy Simulations (LES). In addition, to validate these CFD studies, velocity and turbulence measurements in the wing/floor junction region are also needed.
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Neal, Graeme. "Three-dimensional model testing in the transonic self-streamlining wind tunnel." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/52257/.
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The wall interference effects present on three-dimensional models during wind tunnel testing are difficult to correct using post-test model data correction methods. Further, at transonic speeds, with the use of ventilated test sections these corrections become complex to apply and inaccurate. The high quality of wind tunnel testing that is required today means that such methods are no longer satisfactory. The flexible walled wind tunnel has in recent years shown its ability to obtain two-dimensional aerofoil data free from the effects of wall boundary restraint. This work at Southampton was aimed at extending the use of the two-dimensional Transonic Self-Streaming Wind Tunnel to the relief of wall interference effects on three-dimensional models. The compromise of using only two-wall single curvature movement avoids the problems that are inherent with the additional complexity of fully three-dimensional adaptive tunnels. A method of assessing the wall-induced interference velocity components from tunnel boundary pressure data, without reference to the model, has been developed and validated against other wall interference assessment methods. The algorithm, suitable for use in adaptive tunnels, is used with a wall movement influence coefficient method of wall contour prediction resulting in the apparent removal of wall interference effects along a streamlining target line. The residual wall interference velocity components calculated to be present after streamlining on two half-wing models are significantly lower than their straight test section values. Providing the model span is not too large in comparison with the breadth of the test section, the spanwise interference velocity component is negligible. A calibrated force-balance wing-body model has been used to demonstrate the first successful streamlining around a three-dimensional model in the Transonic Self-Streamlining Wind Tunnel. The measured model force data obtained with streamlined walls compares favourably with that derived using a standard post-test model data correction method.
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Saddington, Alistair J. "Mutual Interference Between Jets and Intakes in STOVL Aircraft." Thesis, Department of Aerospace, Power and Sensors, 2009. http://hdl.handle.net/1826/3895.
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During wind tunnel testing of jet-lift, short take-off and vertical landing (STOVL)
aircraft it is usual to simulate the jet efflux but not the intake flows. The intakes,
which are commonly faired over or are unpowered, are generally tested in separate
wind tunnel experiments. The forces acting on the wind tunnel model are determined
by the linear addition of the forces obtained from the two separate tests.
There is some doubt as to whether this is a valid approach.
A systematic experimental investigation was, therefore, conducted to determine the
magnitude of any jet/intake interference effects on a generic jet-lift STOVL aircraft
in transitional flight, out of ground effect. Comparisons made between separate and
simultaneous jet and intake testing concluded that a mutual jet/intake interference
effect does exist. The existence of this interference means that the aerodynamic wing
lift loss in transitional flight deduced from isolated jet and intake testing is less than
the lift loss obtained from simultaneous jet and intake testing.
The experimental research was supplemented by some simplified computational
fluid dynamics (CFD) studies of elements of the flow-field about the aircraft using
the k-e turbulence model. The numerical modelling enabled aspects of the flow-field
around the aircraft to be visualised which could not easily be done using the experimental
apparatus.
It is a requirement of the Eng]) programme that part of this thesis must address a
management topic linked to the research. In this case the management aspects of
wind tunnel project work were examined. A scenario was developed which established
a requirement for a large-scale, low-speed wind tunnel with a Reynolds number
capability of 20 million. A study was performed on the decision-making process
and investment appraisal methods used in the procurement of such a wind tunnel.
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Rosson, Joel Christopher. "Dynamic flow quality measurements in a transonic cryogenic wind tunnel." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/101463.
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Two instruments mounted in a piggyback arrangement were developed for time-resolved measurements of dynamic flow quality in a transonic cryogenic wind tunnel. The first one is a dual hot-wire aspirating probe for measurement of stagnation pressure and temperature. The second is a miniature high-frequency response angle probe consisting of surface mounted pressure sensors.
The aspirating probe was tested in the 0.3-m Transonic Cryogenic Tunnel (TCT) at NASA-Langley Research Center. Stagnation pressure and temperature measurements were taken in the free-stream of the settling chamber and test section. Data were also obtained in the unsteady wake shed from an airfoil oscillating at 5 Hz. The investigation revealed the presence of large stagnation pressure and temperature fluctuations in the settling chamber occurring at the blade passing frequency of the tunnel driving fan. The fluctuations in the test section are of a much more random nature and have amplitudes much lower than those in the test section. The overall results are consistent with previous tunnel disturbance measurements in the 0.3-m TCT. In the unsteady wake shed from the oscillating airfoil, stagnation temperature fluctuations as high as 42 K rms were observed.
The high-frequency angle probe is a four sensor, pyramid type probe capable of simultaneously measuring time resolved stagnation and static pressures and two orthogonal flow angles. Using measurements from both probes, all flow parameters of interest can be deduced. Aerodynamic behavior of a full size model of the probe was established in an open air jet of known conditions.M.S.
17
Wiggs, Giles F. S. "Airflow over Barchan dunes : field measurements, mathematical modelling and wind tunnel testing." Thesis, University College London (University of London), 1992. http://discovery.ucl.ac.uk/1317535/.
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There are few empirical measurements of velocity, shear velocity, sand transport, morphological change on the windward slopes of dunes.This thesis compares field measurements on a barchan dune in Oman with calculations using a mathematical model (FLOWSTAR) and measurements in a wind tunnel. All three techniques demonstrate similar patterns of velocity, confirming the acceleration of flow up the windward slope, deceleration between the crest and brink and significant flow deceleration upwind of and at the toe of the dune. The FLOWSTAR model is unable accurately to predict airflow at the brink and its predictions near the surface are highly susceptible to small-scale terrain irregularities. The measurements of shear velocity in the field and those predicted by the FLOWSTAR model reflect observations of previous studies including the widely reported upwind reduction in shear velocity. Such a reduction in shear velocity upwind of the dune should result in a reduction in sand transport and sand deposition. This is not observed in the field. Wind tunnel modelling using a near-surface pulse-wire probe suggests that the field and FLOWSTAR methods of shear velocity derivation are inadequate. The wind tunnel results exhibit no reduction in shear velocity upwind of or at the toe of the dune. This maintenance of upwind shear stress may be caused by concave (unstable) streamline curvature, which is not taken into account by the field and FLOWSTAR techniques. From this hypothesis, a new model of dune dynamics is developed relying on the establishment of an equilibrium between windward slope morphology, streamline curvature and streamwise acceleration.
18
Hyvärinen, Ann. "Investigation of blockage correction methods forfull-scale wind tunnel testing of trucks." Thesis, KTH, Flygdynamik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-180436.
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In this work wall interference effects, experienced during full scale wind tunnel testing of trucks, are investigatedthrough simulations. Three different truck models are used, and a number of blockage correction methods areapplied on drag results from simulations in a wind tunnel environment. These are compared with open roadreference simulations. The results indicate that the flow fields around the trucks need to be fairly similar, if thesame correction method is to be used.
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Lehmkuehler, Kai. "A Direct Comparison of Small Aircraft Dynamics between Wind Tunnel and Flight Tests." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16511.
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The miniaturization of embedded electronics and sensors driven by the rapid development of mobile devices has enabled powerful avionics systems for very small aircraft. This enables a potential step forward in accurate flight data gathering for vehicles weighing 5 kg or less. Being able to flight test a small platform like this also allows the comparison of the results with reference data from ground testing in a standard sized wind tunnel of an identical airframe. With this process, the following questions can be answered: Firstly, would such a system then be able to collect accurate flight data for system identification (ID)? Is it possible at all to fly a small, remotely piloted aircraft precisely enough to record the required data, given its sensitivity to atmospheric turbulence, airframe noise, limitations of the remote piloting and so on? And secondly, if accurate data has been obtained, how well do the two experiments match? The small scale might potentially result in previously unknown or at least insignificant physical phenomena, which need to be taken into account when flight testing such a small platform. The changes in the inertial properties of the platform due to the added mass effect is one of these phenomena, which can typically be ignored for full scale aircraft. However, this has proven to be critically important for the successful analysis and comparison of the flight- and wind tunnel data obtained throughout this project. The avionics suite designed for this research was developed in house, since the weight restrictions of the small platform excluded any commercially available flight data recording packages. The suite features an lightweight airdata probe, control surface feedback sensors, a custom designed GPS receiver and many other advanced components previously not possible at this scale. A commercial reference INS was used to benchmark the system. The UAVmainframe also provides basic flight control functionality to aid the pilot in obtaining the required trim conditions and turbulence mitigation. Extensive data compatibility analysis and calibrations were performed on the recorded data using an Extended Kalman Filter (EKF) and various other methods to ensure the best possible data quality. The inertial properties of the test aircraft were determined by swing tests. The significance of the added mass contributions was discovered during these tests, which added up to 25% onto the `true' airframe inertial properties. In an effort to estimate these added mass terms, it has been found that the methods presented in literature to determine the corrections for full scale aircraft do not give the correct results for the small scale aircraft under consideration. Swing tests of a flat plate model of the test aircraft also did not capture the magnitude of the phenomenon correctly, which led to swing tests with a geometrically similar 3-d object of known inertial properties to successfully estimate the added mass corrections. Static derivatives were obtained from conventional wind tunnel testing, in conjunction with a high fidelity three dimensional inviscid solution using the PanAir code. A dynamic test rig was used in the wind tunnel to determine the dynamic derivatives. It allowed the instrumented airframe to rotate freely on a three axis gimbal, essentially 'fly' in the tunnel. The aerodynamic derivatives from these 3 DoF tests were estimated by performing system ID on the recorded data, where the model structures were modified for the reduced set of motion variables. Extensive flight testing was performed at the university's flight test centre. These tests showed the difficulty of testing such a small and light airframe due to wind and airframe noise, as well as the limitations due to lack of feedback received by the remote pilot. The pilot was aided by the flight control system to achieve a good trim condition, and pre-recorded input sequences, similar to the dynamic wind tunnel tests, were used to excite the longitudinal and lateral dynamics of the aircraft. One particular finding during the test campaign was that there is no such thing as totally calm conditions for this scale of airframe. Other findings include a high correlation between the pitch damping term and the pitching moment due to elevator, making it impossible to determine both at the same time, and that in flight the inertial properties of the test aircraft change to the values that include the added mass components, as compared to the dynamic wind tunnel tests, where the `true' inertias are used. By including these findings in the data processing, close agreement between flight and ground test data has been achieved.
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Zientarski, Lauren Ann. "Wind Tunnel Testing of a Variable Camber Compliant Wing with a Unique Dual Load Cell Test Fixture." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1448893315.
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Cedrun, Mark E. "Low-speed wind tunnel testing of the NPS/NASA Ames Mach 6 optimized waverider." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283585.
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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 1994.Thesis advisor(s): Conrad F. Newberry, Jeffrey V. Bowles. "June 1994." Includes bibliographical references. Also available online.
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Talon, Ludovic 1976. "Development of a biofeedback system for optimizing cycling performance assessment during wind tunnel testing." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82259.
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Pereira, Jason L. "Hover and wind-tunnel testing of shrouded rotors for improved micro air vehicle design." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8752.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Broughton, Benjamin Albert. "Low speed wind tunnel testing and data correction methods for aircraft models in ground effect." Diss., University of Pretoria, 1999. http://hdl.handle.net/2263/24292.
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In this thesis, techniques for testing aircraft models in ground effect in a low speed wind tunnel are investigated. Although these types of tests have been done before, the current study is unique in that forces are measured with an overhead balance instead of an internal balance. This has the advantage that the types of models that are difficult to mount on a sting with an internal balance, can often be mounted with a strut protruding from the top of the model. Positioning a sting-mounted model close to the ground at a high angle-of-attack is also usually difficult if not impossible. Finally, drag measurements are often more accurate when measured with an overhead balance rather than with an internal sting-type balance. The disadvantages associated with this method of testing are identified and solutions suggested. These include accurate moment transfers and correcting for support tares and interference. The thesis also investigates general procedures associated with ground effect testing such as proper boundary corrections and the necessity of a rolling floor. A simplified preliminary test series was performed in order to identify shortcomings in the existing equipment and procedures. This series is explained in Chapter 2. Chapter 4 and 5 describe changes made to the existing equipment following this test series. These include a novel telescopic fairing to shroud the mounting strut and an internal pitching mechanism. The correction techniques and general theory are summarised in Chapter 3. The author concludes in Chapter 6 that with the application of the techniques described in this thesis, the test engineer should be able to obtain accurate and reliable data from most aircraft configurations. Additional suggestions for testing models in ground effect are also given in this chapter. Finally, a few shortcomings that still need to be investigated are mentioned at the end of Chapter 6. AFRIKAANS : Hierdie verhandeling ondersoek tegnieke om vliegtuigmodelle in grondeffek in 'n laespoed-windtonnel te toets. Alhoewel hierdie tipe van toetse al voorheen gedoen is, is die huidige studie uniek deurdat 'n oorhoofse balans eerder as 'n interne balans gebruik word. Die voordeel hiervan is dat modelle wat moeilik op 'n naald- of "sting"-balans monteer kan word, baie keer makliker monteer kan word met 'n stang wat deur die bokant van die model steek. Posisioneering van 'n naald-gemonteerde model naby aan die vloer van die tonnel by hoe invalshoeke is gewoonlik ook baie moeilik indien nie onmoontlik nie. Laastens is sleurkrag-metings wat met 'n oorhoofse balans gemeet is gewoonlik meer akkuraat as sleurkrag-metings wat met 'n interne naald-tipe balans gedoen is. Die nadele wat met hierdie toetsmetode geassosieer kan word, word geïdentifiseer en moontlike oplossing word voorgestel. Hierdie sluit die berekening in van akkurate moment-transformasies en monteersleureffekte en -steurings. Die verhandeling ondersoek ook algemene prosedures wat met grondeffektoetse geassosieer kan word, byvoorbeeld akkurate wandkorreksies en die nodigheid van die rolvloer. 'n Vereenvoudigde vooraf-toetsreeks was uitgevoer om moontlike tekortkominge in die bestaande toerusting en prosedures te identifiseer. Hierdie toetsreeks word in Hoofstuk 2 bespreek. Hoofstuk 4 en 5 verduidelik die veranderinge wat aan die bestaande toerusting gemaak is na aanleidng van hierdie toetsreeks. Hierdie veranderinge sluit 'n teleskopiese windskerm in om die monteerstang te isoleer van die wind, sowel as 'n interne heimeganisme om die invalshoek van die model te verstel. Die korreksieprosedures en algemene teorie word in Hoofstuk 3 opgesom. Die outeur se gevolgtekking in Hoofstuk 6 stel dat die toetsingenieur, met behulp van die gebruik van die tegnieke in hierdie verhandeling beskryf, in staat behoort te wees om betroubare metings te kan neem van meeste vliegtuigkonfigurasies. Verdere voorstelle vir die toets van modelle in grondeffek word ook in hierdie hoofstuk gemaak. Uiteindelik word 'n paar tekortkominge genoem wat moontlik in 'n toekomstige studie ondersoek kan word.Dissertation (MEng)--University of Pretoria, 1999.
Mechanical and Aeronautical Engineering
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Broughton, Cabot A. Carleton University Dissertation Engineering Aeronautical. "Experimental investigation of slotted wall wind tunnel test sections for low interference road vehicle testing." Ottawa, 1990.
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Montero, Ryan M. "Analysis, Design and Testing of a Wind Tunnel Model to Validate Fiber-Optic Shape Sensing Systems." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23233.
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The ability to collect valuable data concerning the stress, strains, and shape profiles of aircraft and aircraft components during flight is important to fields such as structural health monitoring, gust alleviation, and flutter control. A research interest in the form of a NASA PhaseI SBIR called for possible systems that would be able to take accurate shape sensing data on a flexible wing aircraft. In a joint venture between Luna Technologies Inc. and Virginia
Polytechnic Institute and State University a flexible wing wind tunnel model was designed and constructed as a test article for the Luna Technologies Inc. fiber optic shape sensing system. In order to prove the capability of a fiber optic shape sensing system in a wind tunnel environment a flexible wing test article was constructed. The wing deflections and twists of the test article were modeled using a vortex lattice method called Tornado combined with simple beam theories. The beam theories were linear beam theories and the stiffness of the composite bodies was supplied by static testing of the test articles. The code was iterative in that it ran the VLM code to estimate the forces and moments on the wing and these were applied to a linear beam which gave the wing a new geometry which in turn was run through the VLM. The wind tunnel model was constructed at Virginia Tech using 3-D printing techniques for the fuselage and foam and fiberglass for the wings. On the bottom surface of the wings the Luna Technologies Inc. fiber optic shape sensing fiber was bonded along the leading and tailing edges. The swept-wing test article was experimentally tested in the Virginia Tech 6\'x6\' Stability Wind Tunnel at various airspeeds and the VLM based code results were in agreement, within margins of error and uncertainty, with the experimental results. The agreement of the analytical and experimental results verified the viability of using an iterative VLM code in combination with simple beam theories as a quick and relatively accurate approximation method for preliminary design and testing. The tests also showed that a fiber optic shape sensing system can be sufficiently tested in a wind tunnel environment, and if applied carefully could perhaps in the future provide useful shape and strain measurements.
Master of Science
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Carlsson, Martin. "Design and Testing of Flexible Aircraft Structures." Doctoral thesis, KTH, Aeronautical and Vehicle Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3761.
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Methods for structural design, control, and testing offlexible aircraft structures are considered. Focus is onnonconventional aircraft con- figurations and control concepts.The interaction between analysis and testing is a central topicand all studies include validation testing and comparisonbetween computational and experimental results.
The first part of the thesis is concerned with the designand testing of an aeroelastic wind-tunnel model representing aBlended Wing Body (BWB) aircraft. The investigations show thata somewhat simplified wind-tunnel model design concept isuseful and efficient for the type of investigations considered.Also, the studies indicate that well established numericaltools are capable of predicting the aeroelastic behavior of theBWB aircraft with reasonable accuracy. Accurate prediction ofthe control surface aerodynamics is however found to bedifficult.
A new aerodynamic boundary element method for aeroelastictimedomain simulations and its experimental validation arepresented. The properties of the method are compared totraditional methods as well as to experimental results. Thestudy indicates that the method is capable of efficient andaccurate aeroelastic simulations.
Next, a method for tailoring a structure with respect to itsaeroelastic behavior is presented. The method is based onnumerical optimization techniques and developed for efficientdesign of aeroelastic wind-tunnel models with prescribed staticand dynamic aeroelastic properties. Experimental validationshows that the design method is useful in practice and that itprovides a more efficient handling of the dynamic aeroelasticproperties compared to previous methods.
Finally, the use of multiple control surfaces andaeroelastic effects for efficient roll maneuvering isconsidered. The idea is to design a controller that takesadvantage of the elasticity of the structure for performancebenefits. By use of optimization methods in combination with afairly simple control system, good maneuvering performance isobtained with minimal control effort. Validation testing usinga flexible wind-tunnel model and a real-time control systemshows that the control strategy is successful in practice.Keywords: aeroelasticity, active aeroelastic structures,aeroelastic tailoring, control, structural optimization,wind-tunnel testing.
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Horton, Damien. "Development of an Infrared Thermography System to Measure Boundary Layer Transition in a Low Speed Wind Tunnel Testing Environment." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2287.
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The use of infrared thermography for boundary layer detection was evaluated for use in the Cal Poly Low Speed Wind Tunnel (LSWT) and recommendations for the successful use of this technique were developed. In cooperation with Joby Aviation, an infinite wing model was designed, manufactured and tested for use in the LSWT. The wing was designed around a custom airfoil profile specific for this project, where the nearly-flat pressure gradient at a zero pitch angle would delay the chordwise onset of boundary layer transition. Steady-state, RANS numerical simulations predicted the onset of transition to occur at 0.75 x/c for the design Reynolds Number condition of 6.25x105. The wing was manufactured from 3D printed aluminum, with a wall thickness of 0.125 inches and a chord length of 13.78 inches. Two central rows of static pressure taps were used, each with 12 functional chordwise locations. The taps were able to generate strong correlation to the numerically predicted pressure coefficient distribution.
The use of an infrared camera visualized and confirmed the presence of boundary layer transition at the chordline location anticipated by the early simulations. To do so, the model was pre-heated such that the differential cooling properties of laminar and turbulent flow would generate a clear temperature gradient on the surface correlating to boundary layer transition. Adjustment of the model’s pitch angle demonstrated a change in the onset location of boundary layer transition during the infrared testing. The change of onset location was seen to move forward along the chordline as the aerodynamic angle of attack was increased. Testing with a Preston Tube system allowed for the interpolation of local skin friction coefficient values at each static tap location. Application of both laminar and turbulent empirical assumptions, when compared to numerical expectations, allowed for the qualitative assessment of boundary layer transition onset. Overall, the wing model developed for this research proved capable of producing quality and repetitive results for the experimental goals it was designed to meet. The model will next be used in continued tests which will further explore the use of infrared thermography.
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Sholtis, Paul M. "Characterization of Upstream Effects Due to High Blockage in the AFRL Vertical Wind Tunnel." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton155594746187138.
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Miranda, Sergio. "Active Control of Separated Flow over a Circular-Arc Airfoil." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34411.
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An experimental study of active control of fully separated flow over a symmetrical circular-arc airfoil at high angles of attack was performed. The experiments were carried out in a low-speed, open circuit wind tunnel. Angles of attack from 10 to 40 degrees were tested. Low-power input, unsteady excitation was applied to the leading or trailing edge shear layers. The actuation was provided by the periodic oscillation of a 4-percent-chord flap placed on the suction side of the airfoil and facing the sharp edge. Vortex-shedding frequencies were measured and harmonic combinations selected as the applied actuator frequencies.
Pressure measurements over the airfoil show that the control increased the normal force coefficient by up to 70%. This supports the idea of vortex capture in the time-averaged sense, enhancing the lift on the airfoil by managing the shear layer roll up.
The results indicate the viability of the control of large-scale flow fields by exploiting the natural amplification of disturbances triggered by small-scale actuators.
The application of flow control on sharp-edged aircraft wings could lead to improved maneuverability, innovative flight control and weight reduction. These can be achieved by inexpensive, low-power, rugged actuators.Master of Science
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Heim, Eugene Henry DeWendt. "Development of Methods for Improved Data Integrity and Efficient Testing of Wind Tunnel Models for Dynamic Test Conditions in Unsteady and Nonlinear Flight Regimes." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31050.
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Todayâ s high performance aircraft are operating in expanded flight envelopes, often maneuvering at high angular rates at high angles-of-attack, even above maximum lift. Current aerodynamic models are inadequate in predicting flight characteristics in the expanded envelope, such as rapid aircraft departures and other unusual motions. Unsteady flows of aircraft are of real concern. The ability to accurately measure aerodynamic loads directly impacts the ability to accurately model and predict flight. Current wind tunnel testing techniques do not adequately address the data fidelity of a test point under the influence of fluctuating loads and moments. Additionally, forced oscillation test techniques, one of the primary tools used to develop dynamic models, do not currently provide estimates of the uncertainty of the results during an oscillation cycle. Further, in testing models across a range of flight conditions, there are frequently parts of the envelope which are well behaved and require few data points to arrive at a sound answer, and other parts of the envelope where the responses are much more active and require a large sample of data to arrive at an answer with statistical significance. Currently, test methods do not factor changes of flow physics into data acquisition schemes, so in many cases data are obtained over more iterations than required, or insufficient data may be obtained to determine a valid estimate. Methods of providing a measure of data integrity for static and forced oscillation test techniques are presented with examples. A method for optimizing required forced oscillation cycles based on decay of uncertainty gradients and balance tolerances is also presented.Master of Science
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Taylor, Nigel John. "Adaptive wall technology for two-dimensional wind tunnel testing at high subsonic through to low supersonic speeds." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294622.
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Sevier, Abigail. "Feasibility Study for Testing the Dynamic Stability of Blunt Bodies with a Magnetic Suspension System in a Supersonic Wind Tunnel." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1493207020743959.
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Child, Malcolm S. (Malcolm Swope). "The design, fabrication, and testing of a wind tunnel for the study of the turbulent transport of aerosols." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/39361.
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Ng, Eton Yat-Tuen, and eton_ng@hotmail com. "Vehicle engine cooling systems: assessment and improvement of wind-tunnel based evaluation methods." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2002. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080422.100014.
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The high complexity of vehicle front-end design, arising from considerations of aerodynamics, safety and styling, causes the airflow velocity profile at the radiator face to be highly distorted, leading to potentially reduced airflow volume for heat dissipation. A flow visualisation study showed that the bumper bar significantly influenced the cooling airflow, leading to three-dimensional vortices in its wake and generating an area of relatively low velocity across at least one third of the radiator core. Since repeatability and accuracy of on-road testing are prejudiced by weather conditions, wind-tunnel testing is often preferred to solve cooling airflow problems. However, there are constraints that limit the accuracy of reproducing on-road cooling performance from wind-tunnel simulations. These constraints included inability to simulate atmospheric conditions, limited tunnel test section sizes (blockage effects) and lack of ground effect simulations. The work presented in this thesis involved use of on-road and wind-tunnel tests to investigate the effects of most common constraints present in wind tunnels on accuracy of the simulations of engine cooling performance and radiator airflow profiles. To aid this investigation, an experimental technique for quantifying radiator airflow velocity distribution and an analytical model for predicting the heat dissipation rate of a radiator were developed. A four-hole dynamic pressure probe (TFI Cobra probe) was also used to document flow fields in proximity to a section of radiator core in a wind tunnel in order to investigate the effect of airflow maldistribution on radiator heat-transfer performance. In order to cope with the inability to simulate ambient temperature, the technique of Specific Dissipation (SD) was used, which had previously been shown to overcome this problem.
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Unal, Sadullah Utku. "Design, Construction And Preliminary Testin Of An Aeroservoelastic Test Apparatus To Be Used In Ankara Wind Tunnel." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607034/index.pdf.
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In this thesis, an aeroservoelastic test appratus is designed to investigate the flutter phenomena in a low speed wind tunnel environment. Flutter is an aeroelastic instability that may occur at control surfaces of aircrafts and missiles. Aerodynamic, elastic, and inertial forces are involved in flutter. A mathematical model using aeroelastic equations of motion is derived to investigate flutter and is used as a basis to design the test setup. Simulations using this mathematical model are performed and critical flutter velocities and frequencies are found. Stiffness characteristics of the test setup are determined using the results of these simulations. The test setup is a two degrees of freedom system, with motions in pitch and plunge, and is controlled by a servomotor in the pitch degree of freedom. A NACA 0012 airfoil is used as a control surface in the test setup. Using this setup, the flutter phenomena is generated in Ankara Wind Tunnel (AWT) and experiments are conducted to validate the results of the theoretical aeroelastic mathematical model calculations.
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Edwards, Alex T. "Comparison of Strain Gage and Fiber Optic Sensors On A Sting Balance In A Supersonic Wind Tunnel." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/30799.
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Force and moment balances have proved to be essential in the measurement and calculation of aerodynamic properties during wind tunnel testing. With the recent advancements of technology, new fiber optic sensors have been designed to replace the conventional foil strain gage sensors commonly found on balances, thereby offering several distinct advantages. The use of fiber optic sensors on a balance brings with it some potential advantages over conventional strain gage balances including increased resolution and accuracy, insensitivity to electromagnetic interference, and the capability of use at high temperatures. By using the fiber optic sensors, some of the limitations of the conventional balance can be overcome, leading to a better overall balance design.
This thesis considers an initial trial application of new fiber optic sensors on a conventional, six-component sting balance while retaining the original foil strain gage sensors for comparison. Tests were conducted with a blunt, 10º half-angle cone model in the Virginia Tech 9x9 inch Supersonic Wind Tunnel at Mach 2.4 with a total pressure of 48 psia and ambient total temperature of 25.3ºC. Results showed a close comparison between the foil strain gages and the fiber optic sensor measurements, which were set up to measure the normal force and pitching moment on the blunt cone model. A Finite Element Model (FEM) of the sting balance was produced in order to determine the best locations for the fiber optic sensors on the sting balance. Computational Fluid Dynamics (CFD) was also used in order to predict and compare the results acquired from all of the sensors.
Master of Science
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Stephens, Arthur William, and arthur stephens esb ie. "Aerodynamic Cooling of Automotive Disc Brakes." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070108.121737.
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Sufficient heat dissipation is crucial to the effective operation of friction based braking systems. Such cooling is generally provided by ensuring a sufficient supply of cooling air to the heated components, hence the aerodynamics in the region of the brake components is extremely important. The objective of the research was to develop an understanding of how aerodynamics could be used to improve the cooling of automotive disc brakes. Two separate sets of wind tunnel experiments were developed. Tests were performed on a vented disc (rotor) to measure the internal flow through the vents on a rotating vented disc under various conditions, including an isolated disc in still air, the disc in still air with the wheel on, the disc in moving air with the wheel on, and an on-road simulation using a ¼ car. On vehicle tests were also performed in a wind tunnel using a purpose built brake test rig. These tests measured the thermal performance of different brake discs under various operating parameters; including constant load braking, and cooling from high temperature under various speeds, wheels and disc types. It was found that airflow through vented rotors was significantly reduced during simulated on-road driving, compared to when measured in isolation, but not particularly affected by the vehicles speed. In the situations tested, vented discs offered a 40+% improvement in cooling over an equivalent sized solid rotors. However the research indicates that the greatest benefit of vented rotors over solid will be in vehicles where air entering the wheel cavity is limited, such as low drag vehicles. It was also found that the most significant improvements in brake thermal performance could be achieved by maximising the airflow into the region of the brake components; including increasing the open area of the wheel, and increasing the vehicle velocity. Other improvements can be achieved by using a wheel material with good conductive capability, and increasing the mass of the disc. Evidence of vortex shedding was also discovered in the airflow at the exit of an internal vented rotor, any reduction in this flow disturbance should lead to increased airflow with associated improvements in thermal performance.
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Pinn, Jarred Michael. "Effect of End-Plate Tabs on Drag Reduction of a 3D Bluff Body with a Blunt Base." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/698.
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This thesis involves the experimental testing of a bluff body with a blunt base to evaluate the effectiveness of end-plate tabs in reducing drag. The bluff body is fitted with interchangeable end plates; one plate is flush with the rest of the exterior and the other plate has small tabs protruding perpendicularly into the flow. The body is tested in the Cal Poly 3ft x 4ft low speed wind tunnel. Testing is conducted in three phases.
The first phase was the hot-wire measurement of streamwise velocity of the near wake behind the bluff body. An IFA300 thermal anemometry system with a hot-wire probe placed behind the model measures the wake velocity fluctuations. The power spectral density on the model without tabs shows large spikes at Strouhal numbers of 0.266, 0.300, and 0.287 at corresponding Re = 41,400, 82,800, 124,200 where vortex shedding occurs. The model with tabs shows no such peaks in power and therefore has attenuated vortex generation in the wake flow at that location.
The second phase of testing was pressure testing the model through the use of pressure ports on the exterior of the bluff body. A Scanivalve pressure transducer measured multiple ports almost simultaneously through tubing that was connected to the model internally and routed through the model’s strut mount and outside of the wind tunnel. This pressure testing shows that the model with tabs is able to achieve up to 36% increase in Cp at Reh = 41,400 on the base region of the bluff body and no negative pressure spikes that occur as a result of vortex shedding.
The last phase of testing is the measurement of total drag on the model through a sting balance mount. This testing shows that the drag on the model is reduced by 14% at Re = 41,400. However it also shows that as velocity increased, the drag reduction is reduced and ultimately negated at Re = 124,200 with no drag loss at all.
The addition of tabs as a passive flow control device did eliminate vortex shedding and alter the base pressure of the bluff body. This particular model however showed no reduction in total drag on the model at high Reynolds numbers higher than 124,000. Further study is necessary to isolate the exact geometry and flow velocities that should be able to produce more favorable drag results for a bluff body with this type of passive flow control device.
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Fu, Tuan-Chun. "Development of Effective Approaches to the Large-Scale Aerodynamic Testing of Low-Rise Building." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/986.
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Low-rise buildings are often subjected to high wind loads during hurricanes that lead to severe damage and cause water intrusion. It is therefore important to estimate accurate wind pressures for design purposes to reduce losses. Wind loads on low-rise buildings can differ significantly depending upon the laboratory in which they were measured. The differences are due in large part to inadequate simulations of the low-frequency content of atmospheric velocity fluctuations in the laboratory and to the small scale of the models used for the measurements. A new partial turbulence simulation methodology was developed for simulating the effect of low-frequency flow fluctuations on low-rise buildings more effectively from the point of view of testing accuracy and repeatability than is currently the case. The methodology was validated by comparing aerodynamic pressure data for building models obtained in the open-jet 12-Fan Wall of Wind (WOW) facility against their counterparts in a boundary-layer wind tunnel. Field measurements of pressures on Texas Tech University building and Silsoe building were also used for validation purposes. The tests in partial simulation are freed of integral length scale constraints, meaning that model length scales in such testing are only limited by blockage considerations. Thus the partial simulation methodology can be used to produce aerodynamic data for low-rise buildings by using large-scale models in wind tunnels and WOW-like facilities. This is a major advantage, because large-scale models allow for accurate modeling of architectural details, testing at higher Reynolds number, using greater spatial resolution of the pressure taps in high pressure zones, and assessing the performance of aerodynamic devices to reduce wind effects. The technique eliminates a major cause of discrepancies among measurements conducted in different laboratories and can help to standardize flow simulations for testing residential homes as well as significantly improving testing accuracy and repeatability. Partial turbulence simulation was used in the WOW to determine the performance of discontinuous perforated parapets in mitigating roof pressures. The comparisons of pressures with and without parapets showed significant reductions in pressure coefficients in the zones with high suctions. This demonstrated the potential of such aerodynamic add-on devices to reduce uplift forces.
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Rainbird, John. "Blockage tolerant wind tunnel testing of aerofoils at angles of incidence from 0 to 360 degrees, with respect to the self-start of vertical-axis wind turbines." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/61575.
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The need for better quality aerofoil data, extending to incidences well beyond stall, for the modelling of vertical-axis wind turbine (VAWT) start-up is established through blade element-momentum modelling. The model is used to show that differences between existing post-stall data are large enough to impact on turbine performance. The differences between the existing aerofoil data are found to result primarily from inconsistencies introduced by wind tunnel blockage and the potential flow-derived formulae used to correct for it. A blockage tolerant wind tunnel test section has been constructed and calibrated for aerofoil testing. The tunnel has two semi-permeable walls made up of an array of transverse aerofoil-shaped slats. It produces free-air equivalent data without the need for blockage corrections. The ratio of slat to open area in the permeable walls that best minimises blockage has been obtained through testing of five different-sized NACA 0015 aerofoils. In free-air, results for the five aerofoils would be identical. The open area ratio that produces the most consistent results for the five aerofoils, based on a standard deviation analysis of the results, is therefore judged to be the best. The aerofoils are tested in a solid-walled wind tunnel, and the data processed using a selection of blockage corrections. The corrections are also judged using a standard deviation analysis. The tolerant tunnel, configured with the best open area ratio, outperforms the best corrections. Comparisons are made between results from the tolerant and solid-walled tunnels for the smallest (least blocked) aerofoil, with the latter corrected for blockage. Results are equal to within experimental error. Three additional aerofoils (a symmetrical NACA 0018 and two cambered versions of it) are tested in the tunnel. Results are used in a numerical study of virtual camber effects on VAWT blades. The effect is found to be significant in turbines with large blade chord to turbine radius ratios. Assessments of Reynolds number effects between 20,000 and 300,000 and camber, for attached and detached blade flows, on forces are presented for all four profiles. A critical Reynolds number is established, above which a laminar separation bubble is able to form on the aerofoil's suction surface. Lift generation before stall improves greatly at supercritical Reynolds numbers. VAWT start-up is modelled using a blade-element momentum method and the new experimental results. A conclusion is reached on the causes of characteristic VAWT start-up behaviour. The turbines enter an idling phase and either get stuck in it due to the presence of a "dead band" of negative torque production at low tip-speed ratios, or exit it into a rapid acceleration to final highest speeds. The behaviour results from blade Reynolds number effects, specifically the large jump in aerofoil performance at the critical Reynolds number. When turbines successfully self-start, blades are able to operate in local flows with supercritical Reynolds number for a sufficient portion of their rotation to slowly accelerate through the idling phase. When they encounter a "dead band" this is not the case.
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Pickhaver, T. W. "Prediction and validation of the aerodynamic effects of simulated battle damage on aircraft wings." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14688.
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Aerodynamic analysis is an important area of survivability studies. There is a desire to be able to predict the aerodynamic effects of a given damage scenario on an aircraft wing with minimal wind tunnel testing or computational simulations. Due to the limited nature of previous studies, this has not generally been possible. The original contribution of this thesis is a predictive technique developed to estimate the aerodynamic effects of a simulated battle damage hole on an aircraft wing, resulting from a range of attack directions. This technique was successfully validated against experimental data. Testing under two-dimensional conditions was undertaken on a NASA LS(1)-0417MOD aerofoil at a Reynolds number of 500,000. This project simulates the effect of attack direction by varying the offset between upper and lower surface damage holes in both chordwise and spanwise directions. Damage was modelled using circular holes. Lift, drag and pitching moment coefficients were measured and supplemented with surface flow visualisation and surface pressure measurements. Coefficient increments, defined as the difference between the damage cases and a datum undamaged case were used to quantify the effects of the damage, with the performance qualified in terms of weak and strong jets. Weak jets were found to have little effect on the flow and aerodynamic properties, while strong jets caused significant disruption. The effects increased in magnitude with hole size, incidence and proximity of the upper surface hole to the pressure peak. Spanwise offset on the holes had little effect on the jet strength but introduced asymmetry into the surface flow. This effect was found to be due to the behaviour of the flow within the cavity. Three-dimensional testing was undertaken at a Reynolds number of 1,000,000 on a half wing model in order to investigate any changes in the aerodynamic characteristics of the damage when applied to a more representative aircraft wing. The higher Reynolds number exploited the larger wind tunnel working section and provided a value more representative of typical unmanned aerial vehicles. As the damage was moved towards the tip its effects were lessened and the transition from weak jet to strong jet delayed. Spanwise pressure variation from the tip also introduced asymmetry into the jet s surface flow features. Plotting coefficient increments for all attack directions against the pressure coefficient difference between upper and lower surfaces from an undamaged wing, across the equivalent damage hole region highlighted significant trends, which were used as the basis of a predictive technique for a range of hole sizes and attack directions. The validity of the technique was assessed by predicting a previously untested damage case and comparing it against subsequent wind tunnel tests. The results from this validation proved encouraging.
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Johnson, Daniel Kenneth. "The Design and Implementation of a Supersonic Indraft Tube Wind Tunnel for the Demonstration of Supersonic Flows." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1862.
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Historically, the endeavor of scale testing flight vehicles at supersonic Mach numbers, especially for long durations, has required the development of closed-loop wind tunnels, which are extremely expensive both to build and operate due to the high complexity and incredible power required to drive such a system. The intermittent blowdown wind tunnel, indraft tunnel, and shock tunnel have alleviated many of these cost requirements to some degree, whilst facilitating testing at very high Mach numbers and enthalpies; however, these systems require the handling of gases at pressures and temperatures that can be prohibitive for many university settings. The Ludwieg tube provides a simple, elegant method for producing testable supersonic flows at price points significantly lower than the aforementioned test-system architectures. Unfortunately, the spacial footprint and moderate cost required for driver tube and nozzle hardware can make it difficult to implement for many non-research universities.
In this thesis, a new supersonic test system architecture is conceived, designed, implemented, and validated for the purpose of making supersonic aerodynamic testing capability attainable for most universities, by combining properties of the Ludwieg Tube and indraft wind tunnel to reduce the cost needed to produce this capability. This system, the Indraft Tube Tunnel, requires no long driver-tube or test-section hardware, aside from a vacuum chamber. Furthermore, it is safe to operate, as high pressure containment systems are not required for the Indraft Tube Tunnel System. It is designed and operated to draw stagnant atmospheric air through a converging-diverging nozzle to achieve a steady-state Mach number of 2.5. Sufficient pressure ratio to reach the desired Mach number is attained by evacuating the vacuum chamber and placing a thin cellophane diaphragm across the inlet of the nozzle, thus separating the vacuum section from ambient atmosphere. To initiate gas flow, the diaphragm is mechanically burst with a puncture device.
This design requires much less hardware to implement than a typical Ludwieg tube, and had an operating cost of less than one dollar per test. Using this method, steady, uninterrupted Mach 2.44 is attained for a duration of 13.6 ms and a test section diameter of 7 inches. The standard deviation of the Mach number measurements is .08 Mach. A shadowgraph imaging setup is used to view and measure the angle of oblique shockwaves on a simple wedge test-model. The Indraft Tube Tunnel is novel in the field of high-speed aerodynamic testing, and may be implemented by other universities to produce supersonic flows with a relatively small investment in hardware and laboratory space.
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Miller, Ryan R. "A SYSTEM FOR MEASURING THE LIFT AND DRAG FORCES OF A SPINNING GOLF BALL HELD FIXED WITHIN A WIND TUNNEL." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/44.
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A system was designed, built and tested in order to test the aerodynamic properties of a standard golf ball in a wind tunnel manufactured by ELD, Inc. model 406(B). The system consists of a rotating shaft, on which the golf ball is attached, connected to a two-axis force transducer. Additionally, an automated data acquisition system was built for enhanced precision of measurements. Data for wind speeds up to 160 ft/s and rotational speeds up to 8,600 rpm were obtained and analyzed. The purpose of the designed apparatus was to allow for studies to better understand the lift and drag coefficients of golf balls during their flight. Subsequent to testing, it was found that the force transducer was not adequate to measure the lift and drag coefficients with sufficient accuracy. Several suggestions have been made on how to improve the wind tunnel so that better results might be obtained in the future.
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Kim, Daeung. "The Application of CFD to Building Analysis and Design: A Combined Approach of an Immersive Case Study and Wind Tunnel Testing." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25140.
Full textAbstract:
Computational Fluid Dynamics (CFD) can play an important role in building design. For all aspects and stages of building design, CFD can be used to provide more accurate and rapid predictions of building performance with regard to air flow, pressure, temperature, and similar parameters.
Generally, the process involved in conducting CFD analyses is relatively complex and requires a good understanding of how best to utilize computational numerical methods. Moreover, the level of skill required to perform an accurate CFD analysis remains a challenge for many professionals particularly architects. In addition, the user needs to input a number of different items of information and parameters into the CFD program in order to obtain a successful and credible solution.
This research seeks to improve the general understanding of how CFD can best be used as a design assistance tool. While there have been a number of quantitative studies suggesting CFD may be a useful tool for building related airflow assessment, few researchers have explored the more qualitative aspects of CFD, in particular developing a better understanding of the procedures required for the proper application of CFD to whole building analysis. This study therefore adopted a combined qualitative and quantitative methodology, with the researcher immersing himself into a case study approach and defining several lessons-learned that are documented and shared. This research will assist practicing architects and architecture students to better understand the application of CFD to building analysis and design.Ph. D.
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Pierce, Warrick Tait. "Evaluation and performance prediction of a wind turbine blade." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1791.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.The aerodynamic performance of an existing wind turbine blade optimised for low wind speed conditions is investigated. The aerodynamic characteristics of four span locations are determined from surface pressure measurements and wake surveys with a traversed five-hole probe performed in a low speed wind tunnel for chord Reynolds numbers ranging from 360,000 - 640,000. Two-dimensional modelling of the wind tunnel tests is performed with the commercial computational fluid dynamics code FLUENT. The predictive accuracies of five eddy-viscosity turbulence models are compared. The computational results are compared to each other and experimental data. It is found that agreement between computational and experimental results varies with turbulence model. For lower Reynolds numbers, the Transitional-SST turbulence model accurately predicted the presence of laminar separation bubbles and was found to be superior to the fully turbulent models considered. This highlighted the importance of transitional modelling at lower Reynolds numbers. With increasing angles of attack the bubbles were found to move towards the leading edge and decrease in length. This was validated with experimental data. For the tip blade section, computations implementing the k-ε realizable turbulence model best predicted experimental data. The two-dimensional panel method code, XFOIL, was found to be optimistic with significantly higher lift-to-drag ratios than measured. Three-dimensional modelling of the rotating wind turbine rotor is performed with the commercial computational fluid dynamics code NUMECA. The Coefficient of Power (Cp) predicted varies from 0.440 to 0.565 depending on the turbulence model. Sectional airfoil characteristics are extracted from these computations and compared to two-dimensional airfoil characteristics. Separation was found to be suppressed for the rotating case. A lower limit of 0.481 for Cp is proposed based on the experimental data.
Centre for Renewable and Sustainable Energy Studies
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Li, Ruilong. "Effects of Architectural Features of Air-Permeable Roof Cladding Materials on Wind-Induced Uplift Loading." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/659.
Full textAbstract:
Widespread damage to roofing materials (such as tiles and shingles) for low-rise buildings, even for weaker hurricanes, has raised concerns regarding design load provisions and construction practices. Currently the building codes used for designing low-rise building roofs are mainly based on testing results from building models which generally do not simulate the architectural features of roofing materials that may significantly influence the wind-induced pressures. Full-scale experimentation was conducted under high winds to investigate the effects of architectural details of high profile roof tiles and asphalt shingles on net pressures that are often responsible for damage to these roofing materials. Effects on the vulnerability of roofing materials were also studied. Different roof models with bare, tiled, and shingled roof decks were tested. Pressures acting on both top and bottom surfaces of the roofing materials were measured to understand their effects on the net uplift loading. The area-averaged peak pressure coefficients obtained from bare, tiled, and shingled roof decks were compared. In addition, a set of wind tunnel tests on a tiled roof deck model were conducted to verify the effects of tiles’ cavity internal pressure. Both the full-scale and the wind tunnel test results showed that underside pressure of a roof tile could either aggravate or alleviate wind uplift on the tile based on its orientation on the roof with respect to the wind angle of attack. For shingles, the underside pressure could aggravate wind uplift if the shingle is located near the center of the roof deck. Bare deck modeling to estimate design wind uplift on shingled decks may be acceptable for most locations but not for field locations; it could underestimate the uplift on shingles by 30-60%. In addition, some initial quantification of the effects of roofing materials on wind uplift was performed by studying the wind uplift load ratio for tiled versus bare deck and shingled versus bare deck. Vulnerability curves, with and without considering the effects of tiles’ cavity internal pressure, showed significant differences. Aerodynamic load provisions for low-rise buildings’ roofs and their vulnerability can thus be more accurately evaluated by considering the effects of the roofing materials.
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Chen, Ru-Ching. "Development of a Supersonic Nozzle and Test Section for use with a Magnetic Suspension System for Re-Entry Aeroshell Models." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1544179612537658.
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Cruz, Juan Ramón. "An Application of Anti-Optimization in the Process of Validating Aerodynamic Codes." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26960.
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An investigation was conducted to assess the usefulness of anti-optimization in the process of validating of aerodynamic codes. Anti-optimization is defined here as the intentional search for regions where the computational and experimental results disagree. Maximizing such disagreements can be a useful tool in uncovering errors and/or weaknesses in both analyses and experiments.
The codes chosen for this investigation were an airfoil code and a lifting line code used together as an analysis to predict three-dimensional wing aerodynamic coefficients. The parameter of interest was the maximum lift coefficient of the three-dimensional wing, CL max. The test domain encompassed Mach numbers from 0.3 to 0.8, and Reynolds numbers from 25,000 to 250,000.
A simple rectangular wing was designed for the experiment. A wind tunnel model of this wing was built and tested in the NASA Langley Transonic Dynamics Tunnel. Selection of the test conditions (i.e., Mach and Reynolds numbers) were made by applying the techniques of response surface methodology and considerations involving the predicted experimental uncertainty. The test was planned and executed in two phases. In the first phase runs were conducted at the pre-planned test conditions. Based on these results additional runs were conducted in areas where significant differences in CL max were observed between the computational results and the experiment â in essence applying the concept of anti-optimization. These additional runs were used to verify the differences in CL max and assess the extent of the region where these differences occurred.
The results of the experiment showed that the analysis was capable of predicting CL max to within 0.05 over most of the test domain. The application of anti-optimization succeeded in identifying a region where the computational and experimental values of CL max differed by more than 0.05, demonstrating the usefulness of anti-optimization in process of validating aerodynamic codes. This region was centered at a Mach number of 0.55 and a Reynolds number of 34,000. Including considerations of the uncertainties in the computational and experimental results confirmed that the disagreement was real and not an artifact of the uncertainties.Ph. D.
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Lopes, Igor Moreira. "EVALUATION OF TRANSITIONS FOR TESTING AGRICULTURAL VENTILATION FANS WITH THE FAN ASSESSMENT NUMERATION SYSTEM (FANS)." UKnowledge, 2012. http://uknowledge.uky.edu/bae_etds/8.
Full textAbstract:
The Fan Assessment Numeration System (FANS) is an improved air velocity traverse method for measuring in situ fan performance. The FANS has been widely used, but variations of its test procedure are commonly employed to accommodate physical or operational barriers encountered in the field. This laboratory study evaluated the use of transitions to connect a 1.37m FANS unit to two smaller fans (1.22m and 0.91m diameter) and one 1.37m diameter fan. Tests were conducted with the FANS unit positioned on both intake and discharge sides of the fans. Three different transition angles (30o, 45o and 60o) and the use of no transition were evaluated. Discharge tests were also performed with no enclosed connection between FANS and fan housings. A different experiment was conducted for each fan size. Data was analyzed by comparing test results to the control with Dunnett’s procedure. Results showed significant differences as much as 5.3% ± 1.20% for intake treatments, 17.2% ± 3.04% for sealed discharge treatments and 37.1% ± 12.24% for discharge treatments with no enclosed connection. All transition angles produced similar fan test results. Differences between test results from the discharge and control treatments increased as differences between FANS and fan dimensions increased.