Dissertations / Theses on the topic 'Active aerodynamics'
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Pesiridis, Apostolos. "Turbocharger turbine unsteady aerodynamics with active control." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498148.
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Brzozowski, Daniel Paul. "Dynamic control of aerodynamic forces on a moving platform using active flow control." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42930.
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The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a two degree-of-freedom traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the trailing edge of the airfoil using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and particle image velocimetry (PIV) measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in both trajectory tracking and disturbance rejection maneuvers. The time-varying aerodynamic lift and pitching moment are estimated from a PIV wake survey using a reduced order model based on classical unsteady aerodynamic theory. These measurements suggest that the entire flow over the airfoil readjusts within 2-3 convective time scales, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.
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Wu, Dong-Nan. "Active bounded-state vibration control for structural applications." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12326.
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Chowdhury, Subhradeep. "An experimental investigation of active stall control in compression systems." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12341.
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Griffin, Steven F. "Acoustic replication in smart structure using active structural/acoustic control." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/13085.
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Alan, Luton J. "Numerical simulations of subsonic aeroelastic behavior and flutter suppression by active control /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020348/.
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Williams, Nathan M. "Active flow control on a nonslender delta wing." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501373.
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The effects of active flow control by oscillatory blowing at the leading edge of a nonslender delta wing with a Λ=50° sweep angle have been investigated. Pressure measurements and Particle Image Velocimetry measurements were conducted on a half wing to investigate the formation of leading edge vortices for oscillatory blowing, compared to the stalled flow for the no blowing case. Stall has been delayed by up to 8, and significant increases in the upper surface suction force have been observed. Velocity measurements show that shear layer reattachment is promoted with forcing, and a vortex flow pattern develops. The time averaged location of the centre of the vortical region moves outboard with increased excitation. The near-surface flow pattern obtained from the PIV measurements shows reattachment in the forward part of the wing. There is no measurable jet-like axial flow in the vortex core, which seems to break down at or very near the apex. This highlights that unlike slender delta wings, vortex breakdown is not a limiting factor in the generation of lift for nonslender delta wings. Phase averaged measurements reveal the perturbation due to the pulsed blowing, its interaction with the shear layer and vortex, apparent displacement of the vortex core, and relaxation of the reattachment region. The flow in a phase averaged sense is highly three dimensional. Experiments indicate that unsteady blowing at Strouhal numbers in the region of St=0.5 to St=0.75, and in the region of St=1.25 to St=1.5 can be a highly effective. Reattached flow can develop from stalled flow after pulsing has been initiated with a time constant of tU/c=5 for unsteady blowing at St=0.75, and tU/c=7 for St=1.5. Experiments with excitation from finite span slots located in the forward half of the wing show that partial blowing can be more effective at low momentum coefficients. Force measurements of a full delta wing confirmed that the effectiveness of this method of flow control was not only confined to half delta wings.
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Stiborová, Dana. "Aktivní aerodynamické prvky osobních vozidel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318777.
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In this diploma thesis active aerodynamic components are designed, specifically brake cooling duct and active automotive wing. Cooling duct prototype and also active regulation controlling electronics including the software were created. Road test was performed to measure the duct parameters. Construction design and the active regulation function of the automotive wing were created. The influence of the wing on aerodynamic characteristics of the car was determined.
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Krichene, Assaad. "Active identification and control of aerodynamic instabilities in axial and centrifugal compressors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12062.
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Kuchan, Abigail. "The integration of active flow control devices into composite wing flaps." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44758.
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Delaying stall is always an attractive option in the aerospace industry. The major benefit of delaying stall is increased lift during takeoff and landings as well as during high angle of attack situations. Devices, such as fluidic oscillators, can be integrated into wing flaps to help delay the occurrence of stall by adding energized air to the airflow on the upper surface of the wing flap. The energized air from the oscillator allows the airflow to remain attached to the upper surface of the wing flap. The fluidic oscillator being integrated in this thesis is an active flow control device (AFC). One common method for integrating any device into a wing flap is to remove a section of the flap and mechanically secure the device. A current trend in the aerospace industry is the increased use of fiber-reinforced composites to replace traditional metal components on aircraft. The traditional methods of device integration cause additional complications when applied to composite components as compared to metal components. This thesis proposes an alternative method for integration of the AFC devices, which occurs before the fabrication of wing flaps is completed and they are attached to the aircraft wing.
Seven design concepts are created to reduce the complications from using current methods of integration on composite wing flaps. The concepts are based on four design requirements: aerodynamics, manufacturing, maintenance, and structure. Four of the design concepts created are external designs, which place the AFC on the exterior surface of the wing flap in two types of grooved channels. The other three designs place the AFC inside the wing flap skin and are categorized as internal designs. In order for the air exiting the AFC to reach the upper surface of the wing flap, slots are created in the wing flap skin for the internal designs. Within each of the seven design concepts two design variants are created based on foam or ribbed core types.
Prototypes were created for all of the external design AFC devices and the side inserted AFC and retaining pieces. Wing flap prototypes were created for the rounded groove straight AFC design, the semi-circular groove with straight AFC, and the side inserted AFC designs. The wing flaps were created using the VARTM process with a vertical layup for the external designs. The rounded groove and semi-circular groove prototypes each went through three generations of prototypes until an acceptable wing flap was created. The side inserted design utilized the lessons learned through each generation of the external design prototypes eliminating the need for multiple generations. The lessons learned through the prototyping process helped refine the designs and determine the ease of manufacturing to be used in the design evaluation.
The evaluation of the designs is based on the four design requirements stated above. The assessment of the designs uses two levels of evaluation matrices to determine the most fitting design concept. As a result of the evaluation, all four of the external designs and one of the internal designs are eliminated. The two remaining internal designs' foam core and ribbed variants are compared to establish the final design selection. The vertically inserted AFC foam core design is the most fitting design concept for the integration of an AFC device into a composite wing flap.
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Erlhoff, Ethan Bruce. "Distributed Forcing on a 3D Bluff Body with a Blunt Base, An Experimental Active Drag Control Approach." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/879.
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This paper seeks to explore the effects of an active drag control method known as distributed forcing on a 3D bluff body with a blunt base. The 9.5 x 15.25 x 3 inch aluminum model constructed for this experiment has an elliptically shaped nose and rectangular aft section. The model is fitted with four, 12 Volt fans, forcing the freestream air into and out of 1 mm thick slots on the upper and lower trailing edges. The forcing is steady in time, held at a constant forcing velocity though all Reynolds numbers, but varies roughly sinusoidally in the spanwise direction across the model. Testing was conducted at Reynolds numbers of 50,000, 100,000 and 150,000 at California Polytechnic State University, San Luis Obispo in the Aerospace Engineering Department’s subsonic 3’ by 4’ wind tunnel.
Effectiveness of the distributed forcing method was evaluated by measuring the base pressure on the model using a Scanivalve system. By measuring multiple static pressure ports, it was found that base pressure increased by 15.3% and 4.2% at Reynolds numbers of 50,000 and 100,000 respectively, and showed a decrease of 2.7% at a Reynolds number of 150,000.
Total drag on the model was also measured using a sting balance mount fitted with strain gauges. This test showed a drag reduction of 15.8% and 5.5% for Reynolds numbers of 50,000 and 100,000 respectively, and an increase in drag of 2.0% at Reynolds number of 150,000, when omitting external power required to run the forcing assembly. The forcing assembly was shown to require nearly 12 times the power to operate than it saves in drag reduction at Reynolds number of 50,000. In addition, a thermal anemometry measurement of streamwise velocity of the near wake behind the bluff body was conducted to qualitatively assess the attenuation of the vortex street behind the model. Distributed forcing shows that as the freestream velocity is increased as compared to the forcing velocity, the change in energy spectral density is lessened, and as such, the largest attenuation in vortex shedding is at Reynolds number of 50,000 while nearly no change is seen at the Reynolds number of 150,000.
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Luton, J. Alan. "Numerical simulations of subsonic aeroelastic behavior and flutter suppression by active control." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/41681.
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A method for predicting the unsteady, subsonic, aeroservoelastic response of a wing has been developed. The air, wing, and control surface are considered to be a single dynamical system. All equations are solved simultaneously in the time domain by a predictor-corrector method. The scheme allows nonlinear aerodynamic and structural models to be used and subcritical, critical, and supercritical aeroelastic behavior may be modeled without restrictions to small disturbances or periodic motions. A vortex-lattice method is used to model the aerodynamics. This method accounts for nonlinear effects associated with high angles of attack, unsteady behavior, and deformations of the wing. The vortex-lattice method is valid as long as separation or vortex bursting does not occur. Two structural models have been employed: a linear model and a nonlinear model which accounts for large curvature. Both models consider the flexural-torsional motion of an inextensional wing.
Master of Science
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Eveker, Kevin M. "Model Development for active control of stall phenomena in aircraft gas turbine engines." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12363.
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Castañeda, Vergara David Armando. "Active Control of Flow over an Oscillating NACA 0012 Airfoil." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203.
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Harrison, Neal A. "Active Flow Control of a Boundary Layer Ingesting Serpentine Diffuser." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34163.
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The use of serpentine boundary layer ingesting (BLI) diffusers offers a significant benefit to the performance of Blended Wing Body aircraft. However, the inherent diffuser geometry combined with a thick ingested boundary layer creates strong secondary flows that lead to severe flow distortion at the engine face, increasing the possibility of engine surge. This study investigated the use of enabling active flow control methods to reduce engine-face distortion.
An ejector-pump based system of fluidic actuators was used to directly manage the diffuser secondary flows. This system was modeled computationally using a boundary condition jet modeling method, and tested in an ejector-driven wind tunnel facility. This facility is capable of simulating the high-altitude, high subsonic Mach number conditions representative of BWB cruise conditions, specifically a cruise Mach number of 0.85 at an altitude of 39,000 ft.
The tunnel test section used for this experiment was designed, built, and tested as a validation tool for the computational methods. This process resulted in the creation of a system capable of efficiently investigating and testing the fundamental mechanisms of flow control in BLI serpentine diffusers at a minimum of time and expense.
Results of the computational and wind tunnel analysis confirmed the large potential benefit of adopting fluidic actuators to control flow distortion in serpentine BLI inlets. Computational analysis showed a maximum 71% reduction in flow distortion at the engine face through the use of the Pyramid 1 ejector scheme, and a 68% reduction using the Circumferential ejector scheme. However, the flow control systems were also found to have a significant impact on flow swirl. The Pyramid 1 ejector scheme was found to increase AIP flow swirl by 64%, while the Circumferential ejector scheme reduced flow swirl by 30%. Computational analyses showed that this difference was the result of jet interaction. By keeping the jet flows separate and distinct, the diffuser secondary flows could be more efficiently managed. For this reason, the most practically effective flow control scheme was the Circumferential ejector scheme.
Experimental results showed that the computational analysis slightly over-predicted flow distortion. However, the trends are accurately predicted despite slight variances in freestream Mach number between runs and a slightly lower tested altitude.Master of Science
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Poole, Sean. "The development of a segmented variable pitch small horizontal axis wind turbine with active pitch control." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020583.
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Small scale wind turbines operating in an urban environment produce dismal amounts of power when compared to their expected output [1-4]. This is largely due to the gusty wind conditions found in an urban environment, coupled with the fact that the wind turbines are not designed for these conditions. A new concept of a Segmented Variable Pitch (SVP) wind turbine has been proposed, which has a strong possibility to perform well in gusty and variable wind conditions. This dissertation explains the concept of a SVP wind turbine in more detail and shows analytical and experimental results relating to this concept. Also, the potential benefits of the proposed concept are mentioned. The results from this dissertation show that this concept has potential with promising results on possible turbine blade aerofoil configurations. Scaled model tests were completed and although further design optimisation is required, the tests showed good potential for the SVP concept. Lastly a proof-of-concept full scale model was manufactured and tested to prove scalability to full size from concept models. Along with the proof-of-concept full scale model, a wireless control system (to control the blade segments) was developed and tested.
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Andrews, Stuart P. "Modelling and simulation of flexible aircraft : handling qualities with active load control." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7705.
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The study of the motion of manoeuvring aircraft has traditionally considered the aircraft
to be rigid. This simplifying assumption has been shown to give quite accurate results for
the flight dynamics of many aircraft types. As modern transport aircraft have developed
however, there has been a marked increase in the size and weight of these aircraft. This
trend is likely to continue with the development of future blended-wing-body and supersonic
transport aircraft. This increase in size and weight has brought about a unique set
of aeroelastic and handling quality issues.
The aerodynamic forces and moments acting on an aeroplane have traditionally been
represented using the aerodynamic derivative approach. It has been shown that this quasisteady
aerodynamic model inadequately predicts the aircraft’s stability characteristics,
and that the inclusion of unsteady aerodynamics “greatly improves the fidelity” of aircraft
models.
This thesis thus presents a novel numerical simulation of an aeroelastic aeroplane for
real-time analysis. The model is built around the standard six degree-of-freedom equations
of motion for a rigid aeroplane using the mean-axes system, and includes unsteady
aerodynamics and structural dynamics. This is suitable for pilot-in-the-loop simulation,
handling qualities and flight loads analysis, and control law development. The dynamics
of the structure are modelled as a set of normal modes, and the equations of motion are
realised in state-space form. The unsteady aerodynamic forces acting on the aeroplane
are described by an indicial state-space model, including unsteady tailplane downwash
and compressibility effects. An implementation of the model is presented in the MATLAB/
Simulink environment.
The interaction between the flight control system, the aeroelastic system and the rigidbody
motion of the aeroplane can result in degraded handling qualities, excessive actuator
control, and fatigue problems. The introduction of load alleviation systems for the management
of loads due to manoeuvres and gusts is also likely to result in the handling
qualities of the aeroplane being degraded.
This thesis presents a number of studies into the impact of structural dynamics, unsteady
aerodynamics, and load alleviation on the handling qualities of a flexible civil transport
aeroplane. The handling qualities of the aeroplane are assessed against a number of
different handling qualities criteria and flying specifications, including the Neal-Smith,
Bandwidth, and CAP criterion. It is shown that aeroelastic effects alter the longitudinal
and lateral-directional characteristics of the aeroplane, resulting in degraded handling
qualities. Manoeuvre and gust load alleviation are similarly found to degrade handling
qualities, while active mode control is shown to offer the possibility of improved handling
qualities.
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Yugulis, Kevin Lee. "High Subsonic Cavity Flow Control Using Plasma Actuators." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345552086.
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Sudak, Peter J. "Experimental Investigation of Active Wingtip Vortex Control using Synthetic Jet Actuators." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1305.
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An experiment was performed in the Cal Poly Mechanical Engineering 2x2 ft wind tunnel to quantify the effect of spanwise synthetic jet actuation (SJA) on the drag of a NACA 0015 semispan wing. The wing, which was designed and manufactured for this experiment, has an aspect ratio of 4.20, a span of 0.427 m (16.813”), and is built around an internal array of piezoelectric actuators, which work in series to create a synthetic jet that emanates from the wingtip in the spanwise direction. Direct lift and drag measurements were taken at a Reynolds Number of 100,000 and 200,000 using a load cell/slider mechanism to quantify the effect of actuation on the lift and drag. It was found that the piezoelectric disks used in the synthetic jet actuators cause structural vibrations that have a significant effect on the aerodynamics of the NACA 0015 model. The experiment was performed in a way as to isolate the effect of vibration from the effect of the synthetic jet on the lift and drag. Lift and drag data was supported with pressure readings from 60 pressure ports distributed in rows along the span of the wing. Oil droplet flow visualization was also performed to understand the effect of SJA near the wingtip.
The synthetic jet and vibration had effects on the drag. The synthetic jet with vibration decreased the drag only slightly while vibration alone could decrease drag significantly from 11.3% at α = 4° to 23.4% at α = 10° and Re = 100,000. The lift was slightly increased with a slight increase due to the jet and showed a slight increase due to vibration. Two complete rows of pressure ports at 2y/b = 37.5% and 85.1% showed changes in lift due to actuation as well. The synthetic jet increased the lift near the wingtip at 2y/b = 85.1% and had little to no effect inboard at the 37.5% location, hence, the synthetic jet changes the lift distribution on the wing. Oil flow visualization was used to support this claim. Without actuation, the footprint of the tip vortex was present on the upper surface of the wing. With actuation on, the footprint disappeared suggesting the vortex was pushed off the wingtip by the jet. It is possible that the increased lift with actuation can be caused by the vortex being pushed outboard.
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Hussain, Ali. "The Effect of Spanwise Location of an Active Boundary Layer Fence on Swept Wing Performance." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555516043121521.
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Walter, Daniel James, and Daniel james walter@gmail com. "Study of aerofoils at high angle of attack in ground effect." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080110.145138.
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Aerodynamic devices, such as wings, are used in higher levels of motorsport (Formula-1 etc.) to increase the contact force between the road and tyres (i.e. to generate downforce). This in turn increases the performance envelope of the race car. However the extra downforce increases aerodynamic drag which (apart from when braking) is generally detrimental to lap-times. The drag acts to slow the vehicle, and hinders the effect of available drive power and reduces fuel economy. Wings, in automotive use, are not constrained by the same parameters as aircraft, and thus higher angles of attack can be safely reached, although at a higher cost in drag. Variable geometry aerodynamic devices have been used in many forms of motorsport in the past offering the ability to change the relative values of downforce and drag. These have invariably been banned, generally due to safety reasons. The use of active aerodynamics is currently legal in both Formula SAE (engineering compet ition for university students to design, build and race an open-wheel race car) and production vehicles. A number of passenger car companies are beginning to incorporate active aerodynamic devices in their designs. In this research the effect of ground proximity on the lift, drag and moment coefficients of inverted, two-dimensional aerofoils was investigated. The purpose of the study was to examine the effect ground proximity on aerofoils post stall, in an effort to evaluate the use of active aerodynamics to increase the performance of a race car. The aerofoils were tested at angles of attack ranging from 0° - 135°. The tests were performed at a Reynolds number of 2.16 x 105 based on chord length. Forces were calculated via the use of pressure taps along the centreline of the aerofoils. The RMIT Industrial Wind Tunnel (IWT) was used for the testing. Normally 3m wide and 2m high, an extra contraction was installed and the section was reduced to form a width of 295mm. The wing was mounted between walls to simulate 2-D flow. The IWT was chosen as it would allow enough height to reduce blockage effect caused by the aerofoils when at high angles of incidence. The walls of the tunnel were pressure tapped to allow monitoring of the pressure gradient along the tunnel. The results show a delay in the stall of the aerofoils tested with reduced ground clearance. Two of the aerofoils tested showed a decrease in Cl with decreasing ground clearance; the third showed an increase. The Cd of the aerofoils post-stall decreased with reduced ground clearance. Decreasing ground clearance was found to reduce pitch moment variation of the aerofoils with varied angle of attack. The results were used in a simulation of a typical Formula SAE race car.
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Walker, Michael Monroe. "Replicating the Effects of a Passive Boundary-Layer Fence via Active Flow Control." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524146958877311.
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Patel, Umesh. "Control authority and the design of active controllers for buffet suppression of the F-15 and F/A-18." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/12161.
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Guskey, Christopher R. "NEAR WALL SHEAR STRESS MODIFICATION USING AN ACTIVE PIEZOELECTRIC NANOWIRE SURFACE." UKnowledge, 2013. http://uknowledge.uky.edu/me_etds/27.
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An experimental study was conducted to explore the possible application of dynamically actuated nanowires to effectively disturb the wall layer in fully developed, turbulent channel flow. Actuated nanowires have the potential to be used for the mixing and filtering of chemicals, enhancing convective heat transfer and reducing drag. The first experimental evidence is presented suggesting it is possible to manipulate and subsequently control turbulent flow structures with active nanowires. An array of rigid, ultra-long (40 μm) TiO2 nanowires was fabricated and installed in the bounding wall of turbulent channel flow then oscillated using an attached piezoelectric actuator. Flow velocity and variance measurements were taken using a single sensor hot-wire with results indicating the nanowire array significantly influenced the flow by increasing the turbulent kinetic energy through the entire wall layer.
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Vasilescu, Roxana. "Helicopter blade tip vortex modifications in hover using piezoelectrically modulated blowing." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-11192004-165246/unrestricted/vasilescu%5Froxana%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2005.Dancila, Stefan, Committee Chair ; Sankar, Lakshmi, Committee Member ; Ruzzene, Massimo, Committee Member ; Smith, Marilyn, Committee Member ; Yu, Yung, Committee Member. Vita. Includes bibliographical references.
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Woszidlo, Rene, and Rene Woszidlo. "PARAMETERS GOVERNING SEPARATION CONTROL WITH SWEEPING JET ACTUATORS." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/203475.
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Parameters governing separation control with sweeping jet actuators over a deflected flap are investigated experimentally on a generic "Multiple Flap Airfoil" (MFA). The model enables an extensive variation of geometric and aerodynamic parameters to aid the scaling of this novel flow control method to full-size applications.Sweeping jets exit from discrete, millimeter-scale nozzles distributed along the span and oscillate from side-to-side. The sweeping frequency is almost linearly dependent on the supplied flowrate per actuator. The measured thrust exerted by a row of actuators agrees well with vectored momentum calculations. Frequency and thrust measurements suggest that the jet velocity is limited to subsonic speeds and that any additional increase in flowrate causes internal choking of the flow.Neither the flowrate nor the momentum input is found to be a sole parameter governing the lift for varying distance between adjacent actuators. However, the product of the mass flow coefficient and the square root of the momentum coefficient collapses the lift onto a single curve regardless of the actuator spacing. Contrary to other actuation methods, separation control with sweeping jets does not exhibit any hysteresis with either momentum input or flap deflection. A comparison between sweeping and non-sweeping jets illustrates the superior control authority provided by sweeping jets. Surface flow visualization on the flap suggests the formation of counter-rotating pairs of streamwise vortices caused by the interaction of neighboring jets.The actuation intensity required to attach the flow increases with increasing downstream distance from the main element's trailing edge and increasing flap deflection. No obvious dependence of the ideal actuation location on actuator spacing, flap deflection, angle of attack, or actuation intensity is found within the tested range. Comparisons between experimental and numerical results reveal that the inviscid flow solution appears to be a suitable predictor for the effectively and efficiently obtainable lift of a given airfoil configuration. The flap size affects the achievable lift, the accompanying drag, and the required flap deflection and actuation intensity. By controlling separation, the range of achievable lift coefficients is doubled without significant penalty in drag even when considering a safety margin for the maximum applicable incidence.
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Mariette, Kevin. "Contrôle en boucle fermée pour la réduction active de traînée aérodynamique des véhicules." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI088.
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Le contrôle actif de l’écoulement à l’arrière des véhicules se déplaçant à grande vitesse est un moyen de diminuer efficacement la consommation énergétique des véhicules par la réduction de la traînée aérodynamique. L’intérêt des méthodes actives est leur possible adéquation avec des conditions environnementales variables pour une modification minimale de la forme des véhicules, contrairement aux systèmes exclusivement passifs (profilage, ailerons aérodynamiques …). Toutefois, le contrôle actif nécessite un apport d’énergie qui réduit sa rentabilité énergétique finale. À l’aide d’essais expérimentaux sur une maquette de véhicule simplifié, cette thèse recherche comment employer un contrôle actif à base de jets pulsés à haute fréquence pour assurer une réduction de traînée de véhicule performante, robuste et énergétiquement rentable. Ces recherches sont axées sur : (i) la compréhension des phénomènes à l’origine de la traînée de pression, (ii) la définition d’un modèle de l’écoulement pour le contrôle, et (iii) l’implémentation expérimentale de méthodes de contrôle de traînée efficaces, robustes et à moindre coût énergétique. Les tests en soufflerie réalisés au cours de cette thèse se basent sur les stratégies de contrôle par mode glissant et de commande par extremum seeking qui permettent de concevoir de nouvelles solutions de réduction de la traînée visant à l’amélioration de la robustesse et de la rentabilité du contrôle par jets pulsés. Cette thèse s’inscrit dans le projet ANR ActivRoad issu de la collaboration de trois laboratoires de recherche : le Laboratoire Ampère (INSA, Lyon), l’Institut Pprime (ENSMA, Poitiers) et le LMFA (Centrale, Lyon) ; et le soutien de deux acteurs industriels : le groupe PSA et Volvo TrucksActive flow control techniques can decrease the aerodynamic drag acting on a vehicle moving at high velocity. Instead of exclusively passive techniques, active control can reduce the pressure drag on a vehicle under a wider range of operating conditions without requiring large modifications of the functional shape of the vehicles. However, active control devices require an additional source of energy, which may decrease the global efficiency of the control. Our work aims to reduce significantly the drag of ground vehicles with efficiency and robustness thanks to high frequency pulsed jet control. We present experimental studies on a simplified bluff body mock-up of a ground vehicle and we seek to understand the phenomena linked to the pressure drag on a vehicle. In this thesis, we propose a modelling methodology of the vehicle’s turbulent wake adapted for control purposes. Finally, we design and test experimentally different closed-loop control methods of the wake with high frequency pulsed air jets. The experimental studies performed in a wind tunnel show the efficient application of sliding mode control and extremum seeking techniques for a robust drag control with energy cost considerations. This thesis was financed by the French National Research Agency (ANR) and contributes to the project ActivRoad involving three French laboratories: Ampère (INSA, Lyon), Pprime Institute (ENSMA, Poitiers), and the LMFA (Centrale, Lyon); and two automotive companies: PSA group and Volvo Trucks
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McHugh, Garrett R. "An Experimental Investigation in the Mitigation of Flutter Oscillation Using Shape Memory Alloys." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1479119992818089.
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Lopera, Javier. "Aerodynamic Control of Slender Bodies from Low to High Angles of Attack through Flow Manipulation." Connect to Online Resource-OhioLINK, 2007. http://www.ohiolink.edu/etd/view.cgi?acc_num=toledo1177504352.
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Littlewood, Rob. "Novel methods of drag reduction for squareback road vehicles." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12534.
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Road vehicles are still largely a consumer product and as such the styling of a vehicle becomes a significant factor in how commercially successful a vehicle will become. The influence of styling combined with the numerous other factors to consider in a vehicle development programme means that the optimum aerodynamic package is not possible in real world applications. Aerodynamicists are continually looking for more discrete and innovative ways to reduce the drag of a vehicle. The current thesis adds to this work by investigating the influence of active flow control devices on the aerodynamic drag of square back style road vehicles. A number of different types of flow control are reviewed and the performance of synthetic jets and pulsed jets are investigated on a simple 2D cylinder flow case experimentally. A simplified ¼ scale vehicle model is equipped with active flow control actuators and their effects on the body drag investigated. The influence of the global wake size and the smaller scale in-wake structures on vehicle drag is investigated and discussed. Modification of a large vortex structure in the lower half of the wake is found to be a dominant mechanism by which model base pressure can be influenced. The total gains in power available are calculated and the potential for incorporating active flow control devices in current road vehicles is reviewed. Due to practicality limitations the active flow control devices are currently ruled out for implementation on a road vehicle. The knowledge gained about the vehicle model wake flow topology is later used to create drag reductions using a simple and discrete passive device. The passive modifications act to support claims made about the influence of in wake structures on the global base pressures and vehicle drag. The devices are also tested at full scale where modifications to the vehicle body forces were also observed.
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Huang, X. "Active control of aerodynamic instabilities." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237877.
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Baleriola, Sophie. "Etude expérimentale de la modification des charges aérodynamiques sur pale d'éolienne par du contrôle d'écoulement actif." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2029/document.
Full textAbstract:
L’énergie éolienne est une source d’énergie propre et renouvelable qui fait partie des moyens pour réduire les émissions de gaz à effet de serre et contrer le réchauffement climatique dans le domaine de la production électrique.L’objectif de la thèse est d’optimiser la production d’énergie éolienne par la réduction des fluctuations de charge induites par la turbulence de la couche limite atmosphérique. Ces fluctuations augmentent la fatigue des pales et réduisent la durée de vie des rotors.Cette réduction des fluctuations de charge est réalisée par le biais d’une approche expérimentale et à l’échelle du laboratoire. Deux actionneurs non conventionnels sont étudiés et testés au sein d’un écoulement contrôlé ensoufflerie: il s’agit d’actionneurs plasma et de jets fluidiques. L’objectif est d’effectuer un contrôle de circulation par une action proche du bord de fuite arrondi de la pale afin de modifier la portance du profil.Dans le cadre du projet SMARTEOLE, les deux stratégies sont d’abord testées en parallèle sur un profil bidimensionnel. Pour cette thèse, les actionneurs plasma sont implémentés autour du bord de fuite arrondi afin d’augmenter ou de réduire la portance. Les performances aérodynamiques ont été modifiées dans la partie linéaire de la courbe de portance. Pour des raisons d’efficacité et de fiabilité, le projet est poursuivi avec des jets fluidiques pour aller vers l’étude des pales et du contrôle d’écoulement en rotation. Ces pales sont préalablement testées dans une configuration translationnelle pour évaluer l’effet du contrôle sans les effets de la rotation. Finalement,les pales sont montées sur le banc éolien du laboratoire. Les effets du contrôle sont mis en évidence par les mesures de pression pariétale et de moment de flexion en pied de pale. Le contrôle induit des réductions importantes de fatigue qui motivent la poursuite des travaux dans le domaine du contrôle d’écoulement appliqué aux pales d’éolienneWind energy is a clean and renewable source of energy that remains one of the solutions to cut carbon emissions and curb global warming in the field of power generation. The present thesis objective is the optimisation of wind energy production by the all eviation of blade load fluctuations induced by shear and turbulence in the atmospheric boundary layer. These fluctuations increase the blade fatigue and reduce the life duration of the rotors.This load fluctuation all eviation is assessed with an experimental approach and at a laboratory scale. Two not conventional flow control strategies, plasma actuators and fluidic jets, are implemented and tested in the controlled environment of a wind-tunnel to perform a circulation control by acting in the vicinity of the rounded trailing-edge of the blade in order to modify its lift force.In the scope of the SMARTEOLE project, both plasma and fluidic strategies are, as a first step, tested in parallel on a 2D-airfoil. For this thesis, plasma actuators are implemented over the airfoil trailing-edge to increase ordecrease the lift force. Airfoil performances are indeed modified in the linear part of the lift curve. For efficiency and reliability reasons, it is chosen to pursue the work towards the rotational configuration with the fluidic strategy. Blades are then manufactured and tested first in a translational configuration to evaluate the potentialof the fluidic actuation without rotational effects. Then, blades are mounted in the wind turbine bench of the laboratory. The effects of the actuation are demonstrated through surface pressure and flapwise bending moment measurements. Actuation shows important fatigue reduction motivating the pursue of the investigations on active flow control applied to wind turbine blades
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Sarwar, Wasim. "Active flow control methods for aerodynamic applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669325.
Full textAbstract:
The cylinder in cross flow has been the subject of many numerical and experimental studies since it provides a deep insight of the physical phenomena occurring in a wide range of flow regimes. Despite a number of investigations at Reynolds number (Re = 3900), there has been a constant debate on the important aspects of the flow such as spanwise resolutions, lateral domain extent, convergence of turbulent statistics in the near wake, the so called U-V streamwise velocity profiles at x = 1D,
where D is the cylinder diameter, and the critical Re for the onset of shear layer instability together with its characterization.
In this thesis, an attempt has been made to address some of these issues and report new results through Direct numerical simulations (DNS) by employing spanwise domain extents i.e. Lz = 1.5D; 2D; 2.5D; pD at the moderate flow regime i.e. Re = 2000, where boundary layer is still laminar while the near wake has gone fully turbulent. Intermittent bursts of shear layer instability have been spotted at this Re indicating the signs of the incipient laminar to turbulent transition in the separating shear layer. It is further confirmed that the secondary instability develops in the regions between the opposite sign large scale spanwise vortices and features a phase lag of 135 degree. Pseudo-Floquet analysis gives a good prediction of fastest growing mode consistent with the reported numerical and experimental measurements.
In the second part of the thesis, active flow control (AFC) past circular cylinder has been thoroughly investigated with the aid of parametric analysis at the same Re. We applied spanwise-dependent fluidic actuation, both steady and time-dependent, on the flow past a circular cylinder at Re = 2000. The actuation takes place in two configurations: in-phase blowing and suction from the slits located at ±90 degree (top and bottom) with respect to the upstream stagnation point for both steady and time periodic actuation, and blowing and suction from the top and bottom slits traveling oppositely with respect to each other in the spanwise direction. Optimal forcing amplitude and wavelength are obtained by sweeping across the parametric space. Spanwise-dependent time-independent forcing with wavelength ¿z = 2D has been found the optimal one in terms of drag reduction and attenuation in lift fluctuations. The time-dependent forcing with sinusoids travelling oppositely with respect to each other along the span produced significant reduction in drag force and lift fluctuations, however, the in-phase time periodic actuation with forcing frequency four times the natural vortex shedding frequency resulted in significant increased drag and lift fluctuation, signalling to a potential candidate for the energy harvesting applications.
Finally, in the last part of the thesis, time-dependence of flow inside novel laminar-fluidic-oscillator has been analyzed using DNS. Again, pseudoFloquet stability analysis has been utilized to predict the fastest growing Fourier modes along the homogeneous direction. Supplementary three-dimensional numerical study has also been conducted for the suitable cases at various Re. It has been found that steady flow inside fluidic oscillator’s cavity bifurcates from steady state to time-periodic state through supercritical Hopf bifurcation. The secondary transition inside fluidic oscillator’s cavity occurs through the breaking of flow symmetry about the cavity axis by pitchfork supercritical bifurcation.El cilindro en flujo cruzado ha sido objeto de muchos estudios numéricos y experimentales, ya que proporciona una visión profunda de los fenómenos físicos que ocurren en una amplia gama de regímenes. A pesar de una serie de investigaciones en el número de Reynolds (Re = 3900), ha habido un debate constante sobre los aspectos importantes del flujo, como las resoluciones en el span, la extensión del dominio lateral, la convergencia de estadísticas turbulentas en la estela cercana, el tipo de perfil (U o V) en la estela a x = 1D, donde D es el diámetro del cilindro, y el Re crítico para el inicio de la inestabilidad de la capa de cizalla y su caracterización. En esta tesis, se han intentado abordar algunos de estos problemas e informar nuevos resultados a través de simulaciones numéricas directas (DNS) mediante el uso de extensiones de dominio spanwise de Lz = 1.5D; 2D; 2.5D; pD en un régimen de flujo transicional a Re = 2000, donde la capa límite todavía es laminar mientras que la estela cercana se ha vuelto completamente turbulenta. A este Re h sido detectada inestabilidad intermitente, lo que indicando una transición incipiente laminar-turbulenta de la capa de cizalla. Se confirma además que la inestabilidad secundaria se desarrolla en las regiones entre los vórtices a gran escala del signo opuesto y presenta un desfase de 135 grados. El análisis de pseudo-Floquet da una buena predicción del modo de crecimiento más rápido consistente con las mediciones numéricas y experimentales reportadas. En la segunda parte de la tesis, el control de flujo activo (AFC) sobre el cilindro circular se ha investigado a fondo con la ayuda de análisis paramétrico al mismo Re. Aplicamos una actuación fluídica dependiente de la envergadura, tanto constante como dependiente del tiempo, en el flujo alrededor de un cilindro circular a Re = 2000. La actuación se realiza en dos configuraciones: soplado y succión en fase desde las ranuras ubicadas a ± 90 grados (arriba y abajo) con respecto al punto de estancamiento aguas arriba (tanto para la actuación periódica constante como dependiente del tiempo), y para el soplado y la succión con dependencia temporal tal que viajan en sentido opuesto a lo largo de las ranuras superior e inferior. La amplitud y la longitud de onda de forzado óptimas se obtienen barriendo el espacio paramétrico. Se ha encontrado que el forzado independiente del tiempo pero de amplitud variable en la envergadura con longitud de onda ¿z = 2D es el óptimo en términos de reducción de la resistencia y atenuación en las fluctuaciones de sustentación. El forzado dependiente del tiempo con sinusoides que viajan en sentido opuesto entre sí a lo largo del tramo produce una reducción significativa en la fuerza de resistencia aerodinámica y la fluctuación de la sustentación, sin embargo, la actuación periódica en el tiempo en fase con una frecuencia de forzado cuatro veces mayor que la frecuencia natura de desprendimiento de vórtices resultó en un aumento significativo de la resistencia y fluctuaciones de sustentación, lo cual lo coloca como potencial candidato para aplicaciones de recolección de energía. Finalmente, en la última parte de la tesis, la dependencia temporal del flujo dentro de un nuevo oscilador fluídico laminar se ha analizado utilizando DNS. Nuevamente, el análisis de estabilidad pseudoFloquet se ha utilizado para predecir los modos de Fourier de más rápido crecimiento en la dirección homogénea. También se ha realizado un estudio numérico tridimensional suplementario para varios de los Re considerados. Se ha encontrado que el flujo constante dentro de la cavidad del oscilador fluídico bifurca del estado estacionario al estado periódico en el tiempo mediante una bifurcación supercrítica de Hopf. La transición secundaria dentro de la cavidad del oscilador fluídico ocurre a través de la ruptura de la simetría del flujo en relación al eje de simetría de la cavidad por bifurcación supercrítica pitchfork.
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Barden, Jason. "Active Aerodynamic Control of Heavy Goods Vehicles." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/9293.
Full textAbstract:
Most heavy goods vehicles in service today are fitted with add-on aerodynamic
devices. The most common of which is the cab-mounted roof deflector. Such devices
provide appreciable drag savings, however, they are often not optimised for the
trailer. When a wind yaw angle is present, their savings also diminish as the yaw
angle increases.
The work conducted within this thesis investigated the possibility of using an
adjustable deflector for active flow control. The optimum deflector height for a given
trailer height was initially investigated using wind tunnel testing. The variation of
this optimum with yaw angle and container separation was then investigated. From
the results a 3D look-up table was generated.
A control scheme was proposed that used the 3D look-up table requiring only
three measurable inputs. The three inputs required were: the wind yaw angle, the
container height and the container separation. A pressure differential located on
the deflector was found to linearly relate to the wind yaw angle. This relationship
allowed on-road measurement of the wind yaw angle and therefore enabled the
development of a prototype controller.
Extensive on-road testing and unsteady computational simulation were conducted.
The results obtained indicated a mean yaw angle magnitude of around
5 perturbed by four fundamental low frequencies. These frequencies were identified
in the runs conducted over the test period and an average frequency established.
Higher frequency disturbances were attributed to the wakes of leading heavy goods
vehicles and were filtered by a suitably chosen numerical filter.
Finally, an estimation of the efficiency of the active device was made using a
combination of simulation and full scale testing.
From the results obtained, an optimised deflector generated an average drag reduction
of 7.4%. An estimated additional drag reduction of 1.9% over the optimised
deflector was predicted through use of an active system.
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Yeshala, Nandita. "A coupled lattice Boltzmann-Navier-Stokes methodology for drag reduction." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37097.
Full textAbstract:
Helicopter performance is greatly influenced by its drag. Pylons, fuselage, landing gear, and especially the rotor hub of a helicopter experience large separated flow regions, even under steady level flight conditions the vehicle has been designed for, contributing to the helicopter drag. Several passive and active flow control concepts have been studied for reducing helicopter drag. While passive flow control methods reduce drag, they do so at one optimized design condition. Therefore, passive drag reduction methods may not work for helicopters that operate under widely varying flight conditions. Active flow control (AFC) methods overcome this disadvantage and consequently are widely being pursued.
The present investigator has studied some of these AFC methods using computational fluid dynamics (CFD) techniques and has found synthetic (or pulsed) jets as one of the more effective drag reduction devices. Two bluff bodies, representative of helicopter components, have been studied and the mechanism behind drag reduction has been analyzed. It was found that the increase in momentum due to the jet, and a resultant reduction in the separated flow region, is the main reason for drag reduction in these configurations. In comparison with steady jets, synthetic jets were found to use less power for a greater drag reduction.
The flow inside these synthetic jet devices is incompressible. It is computationally inefficient to use compressible flow solvers in incompressible regions. In such regions, using Lattice Boltzmann equations (LBE) is more suitable compared to solving the incompressible Navier-Stokes equations. The length scales close to the synthetic jet devices are very small. LBE may be used to better resolve these small length scale regions. However, using LBE throughout the whole domain would be computationally expensive since the grid spacing in the LBE solver has to be of the order of the mean free path. To address this need, a coupled Lattice Boltzmann-Navier-Stokes (LB-NS) methodology has been developed.
The LBE solver has been successfully validated in a standalone manner for several benchmark cases. The solver has also been shown to be of second order accuracy. This LBE solver has been subsequently coupled with an existing Navier-Stokes (NS) solver. Validation of the coupled methodology has been done for analytical problems with known closed form solution.
This LB-NS methodology is further used to simulate the flow past a cylinder where synthetic jet devices have been used to reduce drag. The LBE solver is used in the cavity of the synthetic jet nozzle while the NS solver is employed in the rest of the domain. The cylinder configuration was chosen to demonstrate drag reduction on helicopter hub shape geometries. Significant drag reduction is observed when synthetic jets are used, compared to the baseline no flow control case.
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Metka, Matthew. "Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355.
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Kepets, Mark Alexander 1978. "Actively conformable aerodynamic surfaces." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82226.
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Čermák, Jakub. "Numerická analýza bio-mimetického konceptu řízení proudu na povrchu křídla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-317186.
Full textAbstract:
V této diplomové práci je provedena optimalizace profilu křídla vybaveného elastickou klapkou umístěnou na horní straně profilu. Optimalizační proces je proveden s vyžitím CFD prostředků, konkrétně URANS metody. V prvních kapitolách je popsána historie vývoje křídla vybaveného pohyblivými klapkami. Práce pokračuje popisem a zdůvodněním volby numerické metody. Vytvoření geometrie a výpočetní sítě je krátce popsáno. V práci je také prezentována validace a verifikace dané výpočetní metody. Případová studie je zaměřena na profil LS(1)-0417mod vybavený 20%, 30% a 40% dlouhou, pevnou kalpkou na různých úhlech náběhu. Aerodynamická účinnost společně s proudovým polem je analyzována. Je provedena nelineární pevnostní analýza s využitím MKP programu za účelem vyhodnocení ohybové tuhosti a deformovaného tvaru elastické klapky tak, aby byly splněný podmínky nutné pro automatické vychýlení.
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Guttag, Mark A. (Mark Andrew). "Aerodynamic drag on deformable and active structures in high Reynolds number conditions." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115720.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 141-150).
We explore the effect of topography on the aerodynamic behavior of deformable structures, at high Reynolds numbers. We first introduce a novel mechanism to control the aerodynamic drag on cylinders, in the critical Reynolds number regime. We created both axially grooved and dimpled specimens, comprised of latex membranes stretched over rigid acrylic skeletons. By decreasing the internal pressure of the specimens, the latex stretched inward thus changing the shape of the surface. Using a combination of finite element simulations and precision mechanical experiments, we characterized the relationship between the mechanical deformation in the membrane and pneumatic loading. Wind tunnel experiments were used to explore how changing several geometric parameters, of both grooved and dimpled cylinders, affected the aerodynamic performance. We also used the tunable nature of the specimens to automatically control the dependence of the drag coefficient on the Reynolds number. Additionally, we studied the effect of holes in thin flexible strips at high Reynolds numbers. In this investigation, instead of controlling the deformation of the specimens, we modified the initial geometry by cutting holes in strips and examined the deformation under uniform aerodynamic loading. We used a combined experimental and numerical approach to study the effect of perforation on the drag coefficient. The work presented in this thesis, represents an important first step towards utilizing deformation to control the aerodynamic performance of structures.
by Mark Andrew Guttag.
Ph. D.
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Zink, Paul Scott. "A methodology for robust structural design with application to active aeroelastic wings." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12424.
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Chadwick, Kenneth Michael. "An actively cooled floating element skin friction balance for direct measurement in high enthalpy supersonic flows." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134703/.
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Lassaux, Guillaume 1977. "High-fidelity reduced-order aerodynamic models : application to active control of engine inlets." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82238.
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Silkowski, Peter D. (Peter Daniel). "Aerodynamic design of moveable inlet guide vanes for active control of rotating stall." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/42181.
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Pettit, Gregory William. "Model to Evaluate the Aerodynamic Energy Requirements of Active Materials in Morphing Wings." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/36364.
Full textAbstract:
A computational model is presented which predicts the force, stroke, and energy needed to overcome aerodynamic loads encountered by morphing wings during aircraft maneuvers. This low-cost model generates wing section shapes needed to follow a desired flight path, computes the resulting aerodynamic forces using a unique combination of conformal mapping and the vortex panel method, computes the longitudinal motion of the simulated aircraft, and closes the loop with a zero-error control law. The aerodynamic force prediction method has been verified against two more expensive codes. This overall model will be used to predict the performance of morphing wings and the requirements for the active material actuators in the wings.Master of Science
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Karaolis, Nicos M. "The design of fibre reinforced composite blades for passive and active wind turbine rotor aerodynamic control." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235661.
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Djayapertapa, Lesmana. "A computational method for coupled aerodynamic-structural calculations in unsteady transonic flow with active control study." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341506.
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Shukla, Poorva Jahnukumar. "Active Flight Path Control for an Induced Spin Flight Termination System." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78881.
Full textAbstract:
In this thesis, we describe a method for controlling the cycle-averaged velocity direction of a fixed-wing aircraft in an unpowered, helical descent. While the aircraft propulsion system is disabled, either intentionally or due to a failure, the aerodynamic control surfaces (aileron, elevator, and rudder) are assumed to be functional. Our approach involves two steps: (i) establishing a stable, steady, helical motion for which the control surfaces are not fully deflected and (ii) modulating the aircraft control surfaces about their nominal positions to ``slant'' the helical flight path in a desired direction relative to the atmosphere, whether to attain a desired impact location, to counter a steady wind, or both. The effectiveness of the control law was evaluated in numerical simulations of a general transport model (GTM).Master of Science
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Karadal, Fatih Mutlu. "Active Flutter Suppression Of A Smart Fin." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609830/index.pdf.
Full textAbstract:
This study presents the theoretical analysis of an active flutter suppression methodology applied to a smart fin. The smart fin consists of a cantilever aluminum plate-like structure with surface bonded piezoelectric (PZT, Lead- Zirconate-Titanate) patches.
A thermal analogy method for the purpose of modeling of piezoelectric actuators in MSC®/NASTRAN based on the analogy between thermal strains and piezoelectric strains was presented. The results obtained by the thermal analogy were compared with the reference results and very good agreement was observed. The unsteady aerodynamic loads acting on the structure were calculated by using a linear two-dimensional Doublet-Lattice Method available in MSC®
/NASTRAN. These aerodynamic loads were approximated as rational functions of the Laplace variable by using one of the aerodynamic approximation schemes, Roger&
#8217
s approximation, with least-squares method. These approximated aerodynamic loads together with the structural matrices obtained by the finite element method were used to develop the aeroelastic equations of motion of the smart fin in state-space form. The Hinf robust controllers were then designed for the state-space aeroelastic model of the smart fin by considering both SISO (Single-Input Single-Output) and MIMO (Multi-Input Multi-Output) system models. The verification studies of the controllers showed satisfactory flutter suppression performance around the flutter point and a significant improvement in the flutter speed of the smart fin was also observed.
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Jeřábek, Lukáš. "Aerodynamický návrh posledního stupně parní turbíny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378638.
Full textAbstract:
Diploma thesis deals with calculations of a steam turbine with two uncontrolled extraction points according to the assignment, aerodynamics of the last two stages and operating range with respect to ventilation, range of performance and straining of the last blading under the large condensation pressure deviations. For the first three stages the calculation of prismatic action blades is executed. The fourth and the fifth stages are designed with inconstant reaction over the blades length and their calculation is executed with constant circulation method. For these stages, aerofoil design with respect to their aerodynamic qualities is carried out using Bézier curves. During the whole time verification process of aerofoils qualities, their energy losses and isoentropic Mach number distribution is executed in MISES program in cooperation with Doosan Škoda Power.
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Lahaye, Arnaud. "Caractérisation de l'écoulement autour d'un corps de Ahmed à culot droit." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2019.
Full textAbstract:
Le contrôle actif d’écoulement est actuellement étudié dans le but d’améliorer les performances aérodynamiques des véhicules aériens ou terrestres. La diminution de la traînée permettrait de réduire la consommation de carburants fossiles et donc l’émission des gaz à effet de serre des véhicules. Les actionneurs fluidiques sont utilisés comme dispositifs de contrôle depuis une quinzaine d’année. Le contrôle par jet synthétique semble être le plus adapté à une application sur un véhicule de série dans la mesure où l’actionneur ne doit pas être alimenté en fluide. Le travail présenté dans cette thèse combine l’expérimentation physique et la simulation numérique. Elle s’intéresse tout particulièrement au contrôle de l’écoulement autour d’un corps de Ahmed à culot droit à l’aide d’un actionneur de type jet synthétique. Les essais en soufflerie ont été essentiellement utilisés pour caractériser l’écoulement autour du corps de Ahmed et dans son sillage. L’écoulement autour de cette géométrie simplifiée de véhicule terrestre a été caractérisé par des pesées aérodynamiques, des mesures de pressions pariétales, des acquisitions des fluctuations de vitesse par anémomètrie à fil chaud et des mesures de champs de vitesse par Vélocimétrie par Images de Particules. Les grandeurs moyennes et instationnaires de l’écoulement ont ainsi pu être caractérisées. Les simulations numériques à l’aide du code de calcul elsA ont ensuite été réalisées sur une configuration similaire. Les résultats des simulations de l’écoulement non contrôlé ont été confrontés aux résultats expérimentaux. Dans le but d’agir sur la traînée, le contrôle à l’aide d’un actionneur de type jet synthétique a été réalisé sur la même géométrie. Les paramètres de contrôle tels que la quantité de mouvement, la fréquence d’actionnement et l’orientation des jets synthétiques ont été testés numériquement. Le contrôle à l’aide des paramètres testés, a entrainé une augmentation de la traînée qui est due à une réduction de la longueur de la zone de recirculation associée à une diminution de la pression pariétale au niveau du culot de la maquette. Il ressort de ce travail que le contrôle par jet synthétique à basse fréquence orienté selon le sens principal de l’écoulement semble être une voie à explorerActive flow control is currently studied in order to improve aerial or ground vehicle aerodynamics. Diminishing aerodynamic drag leads to a reduction of fuel consumption and so in greenhouse gas emissions of vehicles. Fluidic actuators have been used as control devices for about fifteen years. Considering the fact that the actuator does not need external fluid supply system, synthetic jet control seems to be the most suitable solution that can fit on production vehicles. This thesis combines experimental tests and numerical simulations. It tackles with the flow control around a square back Ahmed body with synthetic jet actuator. Wind tunnel tests have essentially been used to characterize the flow around and in the wake of the Ahmed body. Flow around this simplified geometry of ground vehicle has been characterized using hot wire anemometry, flush mounted pressure taps and two components Particular Image Velocimetry. The steady and unsteady features of the wake flow have thus been characterized. Simulations of this flow have been performed with the computation code elsA. Results of the simulations of the natural flow around the square back Ahmed body have been compared to experimental results. With a view to modifying the drag, flow control thanks to a synthetic jet actuator has been tested on a square back Ahmed body. Parameters of the flow control, such as momentum coefficient, actuation frequency and orientation of the synthetic jet have been numerically investigated. Results show a decrease of the circulation length leading to a diminution of the base pressure and hence to an increase of the drag. Flow control by using a low frequency with slots oriented along the mainstream seems to be a path to explore