Дисертації: "Turbulent Boundary Layer (TBL)"

1

Nironi, Chiara. "Concentration fluctuations of a passive scalar in a turbulent boundary layer." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00964852.

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This experimental study analyses the dynamics of concentration fluctuations in a passive plume emitted by a point source within the turbulent boundary layer. We aim to extend the popular study of Fackrell and Robins (1982) about concentration fluctuations and fluxes from point sources by including third and fourth moments of concentration. We also further inquire into the influence of source conditions, such as the source size, source elevation and emission velocity, on higher order concentration moments. The data set is completed by a detailed description of the velocity statistics within the TBL, with exhaustive information on both the temporal and spatial structure of the flow. The experimental data-set has been used to test two different modeling ap- proaches: an analytical meandering plume model (in one and in three dimen- sions) and a Lagrangian stochastic micro-mixing model.

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2

Zhang, Yufang. "Coupled convective heat transfer and radiative energy transfer in turbulent boundary layers." Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00969159.

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If radiation plays an important role in many engineering applications, especially in those including combustion systems, influence of radiation on turbulent flows, particularly on the turbulent boundary layers, is still not well known. The objective is here to perform a detailed study of radiation effect on turbulent flows. An optimized emission-based reciprocal (OERM) approach of the Monte-Carlo method is proposed for radiation simulation using the CK model for radiative gas properties. OERM allows the uncertainty of results to be locally controlled while it overcomes the drawback of the original emission-based reciprocity approach by introducing a new frequency distribution function that is based on the maximum temperature of the domain. Direct Numerical Simulation (DNS) has been performed for turbulent channel flows under different pressure, wall temperatures and wall emissivity conditions. Flow field DNS simulations are fully coupled with radiation simulation using the OERM approach. The role of radiation on the mean temperature field and fluctuation field are analyzed in details. Modification of the mean temperature profile leads to changes in wall conductive heat fluxes and new wall laws for temperature when radiation is accounted for. The influence on temperature fluctuations and the turbulent heat flux is investigated through their respective transport equations whose balance is modified by radiation. A new wall-scaling based on the energy balance is proposed to improve collapsing of wall-normal turbulent flux profiles among different channel flows with/without considering radiation transfer. This scaling enables a new turbulent Prandtl number model to be introduced to take into account the effects of radiation. In order to consider the influence of radiation in the near-wall region and predict the modified wall law, a one-dimensional wall model for Large Eddy Simulation (LES) is proposed. The 1D turbulent equilibrium boundary layer equations are solved on an embedded grid in the inner layer. The obtained wall friction stress and wall conductive flux are then fed back to the LES solver. The radiative power term in the energy equation of the 1D wall model is computed from an analytical model. The proposed wall model is validated by a comparison with the former DNS/Monte-Carlo results. Finally, two criteria are proposed and validated. The first one is aimed to predict the importance of wall radiative heat flux while the other one predicts whether a wall model accounting for radiation in the near wall region is necessary. A parametric study is then performed where a k-ǫ model and a turbulent Prandtl number model are applied to simulate the velocity and temperature field of different channel flows under various flow conditions. The obtained criteria values are analyzed and compared.

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3

Ben, Nasr Ouissem. "Numerical simulations of supersonic turbulent wall-bounded flows." Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-01059805.

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This work deals with spatially-evolving supersonic turbulent boundary layers over adiabatic and cold walls at M∞ = 2 and up to Re0 ≈ 2600 using 3 different SGS models. The numerical methodology is based on high-order split-centered scheme to discretize the convective fluxes of the Navier-Stokes equations . For the adiabatic case, it is demonstrated that all SGS models require a comparable minimum grid-refinement in order to capture accurately the near-wall-turbulence. Overall, the models exhibit correct behavior when predictiong the dynamic properties, but show different performances for the temperature distribution in the near-wall region. For the isothermal case, it is found that the compressibility effects are not enhanced due to the wall cooling. As expected, the total temperature fluctuations are not negligible in the near-wall region. The study shows that the anti-correlation linking both velocity and temperature fields, derived from the Morkovin's hypothesis, is not satisfied.

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4

Liu, Bilong. "Acoustical Characteristics of Aircraft Panels." Doctoral thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4102.

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5

Ma, Wei. "Experimental investigation of corner stall in a linear compressor cascade." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00728374.

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In applied research, a lack of understanding of corner stall, i.e. the three-dimensional (3D) separation in the juncture of the endwall and blade corner region, which has limited the efficiency and the stability of compressors. Both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) still need to be calibrated for turbomachinery applications. In the fundamental research of the turbulent boundary layer (TBL), there are a lot of findings of the effects of curvature and pressure gradients, which also play an important role in physics of corner stall. The purpose of this thesis is (i) to carry out an experiment in a cascade, (ii) to gain a database that could be used to calibrate both RANS and LES, and (iii) to give some basic explanations of corner stall through investigating the TBL on the suction side at the mid-span which is more complex than those in the basic investigations but simpler than those in a real engine. A detailed and accurate experiment of 3D flow field through a linear compressor cascade has been set up. Experimental data were acquired for a Reynolds number of 3.82×10 ^5 based on blade chord and inlet flow conditions. Measurements have been achieved by hot-wire anemometry, pressure taps on blade and endwall, five-hole pressure probe, oil visualization, 2D particle image velocimetry (PIV),and two-component laser Doppler anemometry (LDA). An original and complete database was thus obtained. The TBL on the suction side at mid-span was investigated. The wall-normal negative pressure gradient restrains the separation, on the contrary to its influence in the corner stall. The streamwise adverse pressure gradient can be responsible for the development of Reynolds stresses. The remarkable phenomenon at measurement stations near the trailing edge of blade is that an inflection point occurs in each profile of the mean streamwise velocity. At this inflection point, the magnitudes of the Reynolds stresses reach their maximum values, and the direction of energy diffusion also changes. The velocity field in the corner stall was presented. Bimodal histograms of velocity exist in the experiment. The bimodal points mainly appear in the region around the mean interface of separated flow and non-separated flow. At a bimodal point the local two velocity components are non-independent from each other, due to the aperiodic interplay of two basic modes in the flow field. Two modes were proposed to interpret the physics of bimodal behaviour.

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6

Lögdberg, Ola. "Turbulent Boundary Layer Separation and Control." Doctoral thesis, KTH, Linné Flow Center, FLOW, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9821.

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Boundary layer separation is an unwanted phenomenon in most technical applications, as for instance on airplane wings, ground vehicles and in internal flow systems. If separation occurs, it causes loss of lift, higher drag and energy losses. It is thus essential to develop methods to eliminate or delay separation.In the present experimental work streamwise vortices are introduced in turbulent boundary layers to transport higher momentum fluid towards the wall. This enables the boundary layer to stay attached at larger pressure gradients. First the adverse pressure gradient (APG) separation bubbles that are to be eliminated are studied. It is shown that, independent of pressure gradient, the mean velocity defect profiles are self-similar when the scaling proposed by Zagarola and Smits is applied to the data. Then vortex pairs and arrays of vortices of different initial strength are studied in zero pressure gradient (ZPG). Vane-type vortex generators (VGs) are used to generate counter-rotating vortex pairs, and it is shown that the vortex core trajectories scale with the VG height h and the spanwise spacing of the blades. Also the streamwise evolution of the turbulent quantities scale with h. As the vortices are convected downstream they seem to move towards a equidistant state, where the distance from the vortex centres to the wall is half the spanwise distance between two vortices. Yawing the VGs up to 20° do not change the generated circulation of a VG pair. After the ZPG measurements, the VGs where applied in the APG mentioned above. It is shown that that the circulation needed to eliminate separation is nearly independent of the pressure gradient and that the streamwise position of the VG array relative to the separated region is not critical to the control effect. In a similar APG jet vortex generators (VGJs) are shown to as effective as the passive VGs. The ratio VR of jet velocity and test section inlet velocity is varied and a control effectiveness optimum is found for VR=5. At 40° yaw the VGJs have only lost approximately 20% of the control effect. For pulsed VGJs the pulsing frequency, the duty cycle and VR were varied. It was shown that to achieve maximum control effect the injected mass flow rate should be as large as possible, within an optimal range of jet VRs. For a given injected mass flow rate, the important parameter was shown to be the injection time t1. A non-dimensional injection time is defined as t1+ = t1Ujet/d, where d is the jet orifice diameter. Here, the optimal t1+ was 100-200.
QC 20100825

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7

Hystad, Ida. "Numerical Modelling of Turbulent Boundary Layer." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26365.

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Most physical problems involving viscous fluid flows are characterized by turbulence where instabilities and large velocity gradients generate fluctuations in the flow field. Towed sonar arrays are exposed to turbulence in the boundary layer formed around the cable. Problems are related to the cable rotating around its own axis due to variations in tension force caused by the towing vehicle. Numerical calculations of a pressure driven flow along a cylinder are performed for the purpose of investigating the turbulent boundary layer around the cable. In this study, the numerical software OpenFOAM has been used in order to solve the flow field. The Reynolds Average Navier-Stokes (RANS) approach was applied, providing a time-average solution of the flow quantities. The results were used in a comparative study with data obtained from Large Eddy Simulation (LES). Simulations were carried out for two Reynolds numbers based on the shear velocity; Re_tau=[240,550]. The cylinder was assigned two different rotational velocities in addition to a case with zero rotation. Results show that the normalized mean velocity profile is in good agreement with the universal law-of-the-wall and previous published data. Comparison with LES data indicated good agreement with Reynolds shear stresses and the normalized mean velocities in the case of a non-rotating cylinder. However, deviations were observed when rotation was applied. In order to ensure the quality of the numerical results a convergence study was performed. Special attention was paid to the near-wall region in order to capture all levels of the boundary layer.

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8

Lögdberg, Ola. "Turbulent boundary layer separation and control /." Stockholm : Mekanik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9821.

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9

Miller, Teresa S. "Turbulent boundary layer models for acoustic analysis." Diss., Wichita State University, 2011. http://hdl.handle.net/10057/3933.

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An analysis of the three types of turbulent boundary layer (TBL) models for acoustic analysis is presented because current preferred models over-predict TBL contributions to aircraft interior noise predictions. The mean square pressure is a measure of the total energy due to the pressure fluctuations beneath a turbulent boundary layer. The single point wall pressure spectrum sorts the energy into frequencies. The normalized wavenumber-frequency spectrum sorts the energy into wavenumbers. The pressure fluctuations beneath a turbulent boundary layer are found by solving the Poisson equation. In this work, the Poisson equation is solved both numerically and analytically using data from an LES/DES simulation. The numerical solution uses the point Gauss-Seidel method and has reasonable results. The analytical solution uses an eigenvalue expansion method that is less successful. The empirical mean square pressure models predict a relatively large spread in the pressure fluctuation values. It is difficult to draw any meaningful conclusions on which mean square pressure model is preferred when compared to data from the Spirit AeroSystems 6x6 duct. The single point wall pressure spectrum models are evaluated and the two more modern models of Smol’yakov and Goody seem to perform the best. These models are also compared to data from the Spirit AeroSystems 6x6 duct. The spectrum at low frequencies rolled off similar to the Goody model. This analysis indicates that the Goody model is the appropriate single point wall pressure spectrum model for aircraft applications. Important features of the normalized wavenumber-frequency spectrum models are presented and can be classified as either separable or non-separable. Separable models in the Corcos normalized wavenumber-frequency spectrum model class tend to over-predict the response for a range of cases. Both the non-separable Chase 1 and Smol’yakov-Tkachenko models appear to match the M.I.T. low noise, low turbulence wind tunnel data throughout the range of comparison. The Smol’yakov-Tkachenko model does not lend itself to straight forward Fourier transforms needed by the acoustic models. But the Chase 1 model can be converted from wavenumber-frequency spectrum to the cross spectrum, so it is the preferred model for aircraft applications. Therefore, the preferred turbulent boundary layer models for aircraft interior noise predictions are the single point wall pressure spectrum model of Goody and the normalized wavenumber-frequency spectrum model of Chase 1.
Dissertation (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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10

Shaikh, F. N. "Turbulent spots in a transitional boundary layer." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319596.

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11

Belcher, Stephen E. "Turbulent boundary layer flow over undulating surfaces." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279606.

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12

Wikramanayake, Palitha Nalin. "Turbulent wave-current bottom boundary layer flows." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14353.

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13

Brereton, Ashley. "Phytoplankton aggregations in a turbulent boundary layer." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/15833/.

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Phytoplankton aggregations come in a wide range of space and time scales and, as such, simulating such behavior is computationally restrictive. I present a Large-eddy simulation of the upper mixed layer, resolving scales of o(1m). I then show how aggregations are promoted by nutrient upwellings (something which macroscale models struggle to emulate), facilitated primarily by Langmuir circulations. I then demonstrate how certain levels of turbulent mixing encourage planktonic thin layering, a phenomenon which is widely observed.

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14

Lögdberg, Ola. "Vortex generators and turbulent boundary layer separation control." Licentiate thesis, KTH, Mechanics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4152.

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Boundary layer separation is usually an unwanted phenomenon in most technical applications as for instance on airplane wings, on ground vehicles and in internal flows such as diffusers. If separation occurs it leads to loss of lift, higher drag and results in energy losses. It is therefore important to be able to find methods to control and if possible avoid separation altogether without introducing a too heavy penalty such as increased drag, energy consuming suction etc.

In the present work we study one such control method, namely the use of vortex generators (VGs), which are known to be able to hinder turbulent boundary layer separation. We first study the downstream development of streamwise vortices behind pairs and arrays of vortex generators and how the strength of the vortices is coupled to the relative size of the vortex generators in comparison to the boundary layer size. Both the amplitude and the trajectory of the vortices are tracked in the downstream direction. Also the influences of yaw and free stream turbulence on the vortices are investigated. This part of the study is made with hot-wire anemometry where all three velocity components of the vortex structure are measured. The generation of circulation by the VGs scales excellently with the VG blade height and the velocity at the blade edge. The magnitude of circulation was found to be independent of yaw angle.

The second part of the study deals with the control effect of vortex generators on three different cases where the strength of the adverse pressure gradient (APG) in a turbulent boundary layer has been varied. In this case the measurements have been made with particle image velocimetry. It was found that the streamwise position where the VGs are placed is not critical for the control effect. For the three different APG cases approximately the same level of circulation was needed to inhibit separation. In contrast to some previous studies we find no evidence of a universal detachment shape factor H_12,that is independent of pressure gradient.

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15

Lögdberg, Ola. "Vortex generators and turbulent boundary layer separation control /." Stockholm : Department of Mechanics, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4152.

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16

Renoud, Robert W. "Boundary layer response to an unsteady turbulent environment." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22931.

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17

Erm, Lincoln. "Low-Reynolds-number turbulent boundary layers /." Connect to thesis, 1988. http://eprints.unimelb.edu.au/archive/00000226.

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18

Mackerrell, O. S. "Some hydrodynamic instabilities of boundary layer flows." Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381355.

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19

Hernandez, Medina Santiago. "Turbulent interface phenomena in a temporally developing boundary layer." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14721/.

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The purpose of the current study was to examine the characteristics and behavior of the turbulent/non-turbulent interface on a temporally developing boundary layer. Flow topology, turbulent statistics, enstrophy budgets and spectral statistics were computed with the purpose of acquiring meaningful results.

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20

Skote, Martin. "Studies of turbulent boundary layer flow throughdirect numerical simulation." Doctoral thesis, KTH, Mechanics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3089.

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21

Angele, Kristian. "Experimental studies of turbulent boundary layer separation and control." Doctoral thesis, KTH, Mechanics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3565.

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The object ofthe present work is to experimentally study thecase ofa turbulent boundary layer subjected to an AdversePressure Gradient (APG) with separation and reattachment. Thisconstitutes a good test case for advanced turbulence modeling.The work consists ofde sign of a wind-tunnel setup, developmentofP article Image Velocimetry (PIV) measurements and evaluationtechniques for boundary layer flows, investigations ofs calingofb oundary layers with APG and separation and studies oftheturbulence structure ofthe separating boundary layer withcontrol by means ofs treamwise vortices. The accuracy ofP IV isinvestigated in the near-wall region ofa zero pressure-gradientturbulent boundary layer at high Reynolds number. It is shownthat, by careful design oft he experiment and correctly appliedvalidation criteria, PIV is a serious alternative toconventional techniques for well-resolved accurate turbulencemeasurements. The results from peak-locking simulationsconstitute useful guide-lines for the effect on the turbulencestatistics. Its symptoms are identified and criteria for whenthis needs to be considered are presented. Different velocityscalings are tested against the new data base on a separatingAPG boundary layer. It is shown that a velocity scale relatedto the local pressure gradient gives similarity not only forthe mean velocity but also to some extent for the Reynoldsshear-stress. Another velocity scale, which is claimed to berelated to the maximum Reynolds shear-stress, gives the samedegree of similarity which connects the two scalings. However,profile similarity achieved within an experiment is notuniversal and this flow is obviously governed by parameterswhich are still not accounted for. Turbulent boundary layerseparation control by means ofs treamwise vortices isinvestigated. The instantaneous interaction between thevortices and the boundary layer and the change in the boundarylayer and turbulence structure is presented. The vortices aregrowing with the boundary layer and the maximum vorticity isdecreased as the circulation is conserved. The vortices arenon-stationary and subjected to vortex stretching. Themovements contribute to large levels ofthe Reynolds stresses.Initially non-equidistant vortices become and remainequidistant and are con- fined to the boundary layer. Theamount ofi nitial streamwise circulationwas found to be acrucial parameter for successful separation control whereas thevortex generator position and size is ofseco ndary importance.At symmetry planes the turbulence is relaxed to a nearisotropic state and the turbulence kinetic energy is decreasedcompared to the case without vortices.

Keywords:Turbulence, Boundary layer, Separation,Adverse Pressure Gradient (APG), PIV, control, streamwisevortices, velocity scaling.

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22

Badr, Mohammad Ali. "Shock wave turbulent boundary layer interaction over a protrusion." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3942.

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This research attempts to investigate an important and common phenomenon in aerodynamics called shock interaction in a turbulent flow’s boundary layer. Due to advancements in current computational units, more complex geometries could be simulated with providing more accurate results. The tools used in this investigation are computational turbulent model of hybrid RANS/LES, called detached eddy simulation (DES). DES and its variant delayed detached eddy simulation (DDES) were the two computational schemes used for numerical simulation. Two protrusions were focused on in this work: a symmetrical bump and a proposed aircraft UHF antenna. Computation where performed with commercial software Cobalt and FLUENT in the High Performance Computing Center (HiPeCC) in Wichita State University. Computational simulation is costly in terms of energy consumption and time usage. Even so with the advanced computational units of HiPeCC, using in average of 18 processors, total simulation for this research took over 2 months of simulation.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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23

Gwilliam, David J. "Separating boundary layer response to an unsteady turbulent environment." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/27259.

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24

Kral, Linda Dee. "Numerical investigation of transition control of a flat plate boundary layer." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184621.

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A numerical model has been developed for investigating boundary layer transition control for a three-dimensional flat plate boundary layer. Control of a periodically forced boundary layer in an incompressible fluid is studied using surface heating techniques. The spatially evolving boundary layer is simulated. The Navier-Stokes and energy equations are integrated using a fully implicit finite difference/spectral method. The Navier-Stokes equations are in vorticity-velocity form and are coupled with the energy equation through the viscosity dependence on temperature. Both passive and active methods of control by surface heating are investigated. In passive methods of control, wall heating is employed to alter the stability characteristics of the mean flow. Both uniform and nonuniform surface temperature distributions are studied. In the active control investigations, temperature perturbations are introduced locally along finite heater strips to directly attenuate the instability waves in the flow. A feedback control loop is employed in which a downstream sensor is used to monitor wall shear stress fluctuations. Passive control of small amplitude two-dimensional Tollmien-Schlichting waves and three-dimensional oblique waves are numerically simulated with both uniform and nonuniform passive heating applied. Strong reductions in both amplitude levels and amplification rates are achieved. Active control of small amplitude two-dimensional and three-dimensional disturbances is also numerically simulated. With proper phase control, in phase reinforcement and out of phase attenuation is demonstrated. A receptivity study is performed to study how localized temperature perturbations are generated into Tollmien-Schlichting waves. It is shown that narrow heater strips are more receptive in that they maximize the amplitude level of the disturbances in the flow. It is also found that the local temperature fluctuations cause mainly a strong normal gradient in spanwise vorticity. Control of the early stages of the nonlinear breakdown process is also investigated. Uniform passive control is applied to both the fundamental and sub-harmonic routes to turbulence. A strong reduction in amplitude levels and growth rates results. In particular, the three-dimensional growth rates are significantly reduced below the uncontrolled levels. Active control of the fundamental breakdown process is also numerically simulated. Control is achieved using either a two-dimensional or three-dimensional control input.

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25

Ha, Siew-Mun. "An experimental study of coherent structures in a three-dimensional turbulent boundary layer." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07122007-103942/.

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26

Ahn, Seungki. "Some unsteady features of turbulent boundary layers." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53090.

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For steady free-stream, zero and favorable pressure gradient turbulent boundary layers, the unsteadiness in the form of turbulent fluetuations was investigated. Phase ensemble-averaged flow characteristics of a large amplitude periodic unsteady turbulent boundary layer was also investigated at a redueed frequency k = 0.61 based on the length of the eonverging and diverging test section with amplitude to mean velocity ratio of 0.8. ln steady flow cases, both zero and favorable pressure gradient flows show good two—dimensional flow characteristics and mean flow characteristics are compared with other researchers’ data. Measured power spectral data show good agreement with those of Klebanoff, Ueda and Hinze, Perry, Lim and Henbest for the zero pressure gradient flows and Jones and Launder for the favorable pressure gradient flow. The power spectral data measured in the turbulent wall region of the zero pressure gradient flow closely follow the model equation proposed by Perry, Lim and Henbest. Convective wave speed also show good agreement with those of Favre, Gaviglio and Dumas and Sternberg within the experimental uncertainties. ln the inner region of the boundary layer where y+ < 40, convective wave speed is higher than local mean velocity at all eddy scales as observed by Kline, Reynolds, Schraub and Runstadler. In the unsteady flow case, in the absence of flow reversal, the flow behaves in a quasi-steady manner and can be described by the steady flow structure as in the case of moderate amplitude flows. The Ludwieg·Tillmann skin friction equation and the Perry-Schofield universal velocity defect law hold at these phases. Except the laminariscent velocity profile observed during the acceleration phases, the large amplitude unsteady flow shows basically the same flow characteristics as the moderate amplitude flows.
Master of Science

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27

Ailinger, Kevin Gerard. "Measurements of surface shear stresses under a three-dimensional turbulent boundary layer using oil-film laser interferometry." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11012008-063040/.

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28

Johnstone, Henry Webb 1956. "CONFINED JET-INDUCED MIXING AT A DENSITY INTERFACE (TURBULENT, SHEAR FLOW)." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/292003.

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29

Österlund, Jens M. "Experimental studies of zero pressure-gradient turbulent boundary layer flow." Doctoral thesis, KTH, Mechanics, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2894.

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30

Efros, Vladislav. "Structure of turbulent boundary layer over a 2-D roughness." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13214.

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The roughness is an important parameter in wall-bounded flows, as most surfaces are rough. The main effect of the roughness is to increase the drag as the near wall is affected by the roughness. In recent years a lot of efforts has been used to find out what effect has the roughness on the outer layer. In other words is there any differences in outer layer, boundary layer or channel flow, between rough and smooth-surface? Jimenez (2004) suggests that for δ/k > 40 there are no differences, in agreement with Townsend’s hypothesis, the roughness merely acts to increase the surface stresses, without changing the structure in the flow. This was challenged by Krogstad et. al (1999) who showed, for boundary layer over 2−D roughness, there is a difference in the outer layer due to the roughness. However for a channel flow Krogstad et. al (2004) has found no differences. The main impediment is how to obtain a reliable estimate for the friction velocity, uτ, which is the main scaling parameter of principal interest. In channel flow the uτ may be obtained directly from the stream-wise pressure gradient. A common technique for boundary layer over smooth surface is the Clauser chart. This method is subjected to large uncertainties for rough surface, because the number of unknowns is increased from one, Cf , for smooth surface to three, (Cf , _, the shift in origin and Δu/uτ shift in velocity), for rough surface. The need for an independent measurement of the wall shear stress has led to the present work. A floating-balance has been designed to obtain the shear stress on the rough surface. The balance was tested in channel flow, adverse pressure gradient flow and zero pressure gradient boundary layer and the velocity field was investigated using a two-component LDA system. The results showed that the shear stress, from balance, was underestimated by ∼ 4%. Turbulent boundary layer is a complicated nonlinear system; Clauser (1956) compared it with a black box. A better understanding of this system may be obtained by changing one of its inputs and to examine its output. An experimental investigation on the response of a turbulent boundary layer to sudden change in roughness, from smooth to rough, using floating balance to measure the shear stress is also a part of the present work. The structure of the turbulent boundary layer over 2 − D roughness was invesitigated using LDA and PIV system. All the moments up to third order were determined from the LDA measurements. From the PIV measurements twopoint correlations in x − y plane were obtained. The effect of large scales on the features of the flow-using POD was also investigated

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31

Ferro, Marco. "Experimental study on turbulent boundary-layer flows with wall transpiration." Doctoral thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217125.

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Wall transpiration, in the form of wall-normal suction or blowing through a permeable wall, is a relatively simple and effective technique to control the behaviour of a boundary layer. For its potential applications for laminar-turbulent transition and separation delay (suction) or for turbulent drag reduction and thermal protection (blowing), wall transpiration has over the past decades been the topic of a significant amount of studies. However, as far as the turbulent regime is concerned, fundamental understanding of the phenomena occurring in the boundary layer in presence of wall transpiration is limited and considerable disagreements persist even on the description of basic quantities, such as the mean streamwise velocity, for the rather simplified case of flat-plate boundary-layer flows without pressure gradients. In order to provide new experimental data on suction and blowing boundary layers, an experimental apparatus was designed and brought into operation. The perforated region spans the whole 1.2 m of the test-section width and with its streamwise extent of 6.5 m is significantly longer than previous studies, allowing for a better investigation of the spatial development of the boundary layer. The quality of the experimental setup and measurement procedures was verified with extensive testing, including benchmarking against previous results on a canonical zero-pressure-gradient turbulent boundary layer (ZPG TBL) and on a laminar asymptotic suction boundary layer. The present experimental results on ZPG turbulent suction boundary layers show that it is possible to experimentally realize a turbulent asymptotic suction boundary layer (TASBL) where the boundary layer mean-velocity profile becomes independent of the streamwise location, so that the suction rate constitutes the only control parameter. TASBLs show a mean-velocity profile with a large logarithmic region and without the existence of a clear wake region. If outer scaling is adopted, using the free-stream velocity and the boundary layer thickness (δ99) as characteristic velocity and length scale respectively, the logarithmic region is described by a slope Ao=0.064 and an intercept Bo=0.994, independently from the suction rate (Γ). Relaminarization of an initially turbulent boundary layer is observed for Γ>3.70×10−3. Wall suction is responsible for a strong damping of the velocity fluctuations, with a decrease of the near-wall peak of the velocity-variance profile ranging from 50% to 65% when compared to a canonical ZPG TBL at comparable Reτ. This decrease in the turbulent activity appears to be explained by an increased stability of the near-wall streaks. Measurements on ZPG blowing boundary layers were conducted for blowing rates ranging between 0.1% and 0.37% of the free-stream velocity and cover the range of momentum thickness Reynolds number 10000<Reθ<36000. Wall-normal blowing strongly modifies the shape of the boundary-layer mean-velocity profile. As the blowing rate is increased, the clear logarithmic region characterizing the canonical ZPG TBLs gradually disappears. A good overlap among the mean velocity-defect profiles of the canonical ZPG TBLs and of the blowing boundary layers for all the Re number and blowing rates considered is obtained when normalization with the Zagarola-Smits velocity scale is adopted. Wall blowing enhances the intensity of the velocity fluctuations, especially in the outer region. At sufficiently high blowing rates and Reynolds number, the outer peak in the streamwise-velocity fluctuations surpasses in magnitude the near-wall peak, which eventually disappears.
Genom att använda sig av genomströmmande ytor, med sugning eller blåsning, kan man relativt enkelt och effektivt påverka ett gränsskikts tillstånd. Genom sin potential att påverka olika strömningsfysikaliska fenomen så som att senarelägga både avlösning och omslaget från laminär till turbulent strömning (genom sugning) eller som att exempelvis minska luftmotståndet i turbulenta gränsskikt och ge kyleffekt (genom blåsning), så har ett otaligt antal studier genomförts på området de senaste decennierna. Trots detta så är den grundläggande förståelsen bristfällig för de strömningsfenomen som inträffar i turbulenta gränsskikt över genomströmmande ytor. Det råder stora meningsskiljaktigheter om de mest elementära strömningskvantiteterna, såsom medelhastigheten, när sugning och blåsning tillämpas även i det mest förenklade gränsskiktsfallet nämligen det som utvecklar sig över en plan platta utan tryckgradient. För att ta fram nya experimentella data på gränsskikt med sugning och blåsning genom ytan så har vi designat en ny experimentell uppställning samt tagit den i bruk.Den genomströmmande ytan spänner över hela bredden av vindtunnelns mätsträcka (1.2 m) och är 6.5 m lång i strömningsriktningen och är därmed betydligt längre än vad som använts i tidigare studier. Detta gör det möjligt att bättre utforska gränsskiktet som utvecklas över ytan i strömningsriktningen. Kvaliteten på den experimentella uppställningen och valda mätprocedurerna har verifierats genom omfattande tester, som även inkluderar benchmarking mot tidigare resultat på turbulenta gränsskikt utan tryckgradient eller blåsning/sugning och på laminära asymptotiska sugningsgränsskikt. De experimentella resultaten på turbulenta gränsskikt med sugning bekräftar för första gången att det är möjligt att experimentellt sätta upp ett turbulent asymptotiskt sugningsgränsskikt där gränsskiktets medelhastighetsprofil blir oberoende av strömningsriktningen och där sugningshastigheten utgör den enda kontrollparametern. Det turbulenta asymptotiska sugningsgränsskiktet visar sig ha en medelhastighetsprofil normalt mot ytan med en lång logaritmisk region och utan förekomsten av en yttre vakregion. Om man använder yttre skalning av medelhastigheten, med friströmshastigheten och gränsskiktstjockleken som karaktäristisk hastighet respektive längdskala, så kan det logaritmiska området beskrivas med en lutning på Ao=0.064 och ett korsande värde med y-axeln på Bo=0.994, som är oberoende av sugningshastigheten. Om sugningshasigheten normaliserad med friströmshastigheten överskrider värdet 3.70x10^-3 så återgår det ursprungligen turbulenta gränsskiktet till att vara laminärt. Sugningen genom väggen dämpar hastighetsfluktuationerna i gränsskiktet med upp till 50-60% vid direkt jämförelse av det inre toppvärdet i ett turbulent gränsskikt utan sugning och vid jämförbart Reynolds tal. Denna minskning av turbulent aktivitet verkar härstamma från en ökad stabilitet av hastighetsstråken närmast ytan. Mätningar på turbulenta gränsskikt med blåsning har genomförts för blåsningshastigheter mellan 0.1 och 0.37% av friströmshastigheten och täcker Reynoldstalområdet (10-36)x10^3, med Reynolds tal baserat på rörelsemängds-tjockleken. Vid blåsning genom ytan får man en stark modifiering av formen på hastighetesfördelningen genom gränsskiktet. När blåsningshastigheten ökar så kommer till slut den logaritmiska regionen av medelhastigheten, karaktäristisk för turbulent gränsskikt utan blåsning, att gradvis försvinna. God överens-stämmelse av medelhastighetsprofiler mellan turbulenta gränsskikt med och utan blåsning erhålls för alla Reynoldstal och blåsningshastigheter när profilerna normaliseras med Zagarola-Smits hastighetsskala. Blåsning vid väggen ökar intensiteten av hastighetsfluktuationerna, speciellt i den yttre regionen av gränsskiktet. Vid riktigt höga blåsningshastigheter och Reynoldstal så kommer den yttre toppen av hastighetsfluktuationer i gränsskiktet att överskrida den inre toppen, som i sig gradvis försvinner.

QC 20171101

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32

Zhang, Fan. "The modelling of particle resuspension in a turbulent boundary layer." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1372.

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The work presented concerns the way small particles attached to a surface are resuspended when exposed to a turbulent flow. Of particular concern to this work is the remobilization of radioactive particles as a consequence of potential nuclear accidents. In this particular case the focus is on small particles, < 5 microns in diameter, where the principal force holding such particles onto a surface arises from van der Waals inter-molecular forces. Given its suitable treatment of the microphysics of small particles, it was decided here to aim to develop improved versions of the Rock’n’Roll (R’n’R) model; the R’n’R model is based on a statistical approach to resuspension involving the rocking and rolling of a particle about surface asperities induced by the moments of the fluctuating drag forces acting on the particle close to the surface. Firstly, a force (moment) balance model has been modified by including the distribution of the aerodynamic force instead of considering only its mean value. It was also possible to improve the representation of the adhesive-force distribution where it is customary to include a substantial reduction factor to take account of surface roughness. The R’n’R model is significantly improved by using realistic statistical fluctuations of both the stream-wise fluid velocity and acceleration close to the wall obtained from Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) of turbulent channel flow; in the standard model a major assumption is that these obey a Gaussian distribution. The flow conditions are translated into the moments of the drag force acting on the particle attached to the surface (using O’Neill’s formula for the aerodynamic drag forces in terms of the local flow velocities). In so doing the influence of highly non-Gaussian forces (associated with the sweeping and ejection events in a turbulent boundary layer) on the resuspension rate has been examined along with the sensitivity of the fluctuation statistics to LES and DNS. We have found most importantly that the statistics of both fluctuating forces and its derivative (normalized on their rms values) are noticeably independent of the normalized distance from the wall, y+ within the viscous sublayer (y+ < 6) – if this were not the case then modelling fluctuations with different particle sizes would be far more complex. In particular as a result of the analysis of our DNS/LES data 3 distinct features of the modified R’n’R model have emerged as playing an important part in the resuspension. The first is the typical forcing frequency ω due to the turbulent (fluctuating) aerodynamic drag forces acting on the particle attached to a surface (in the modified R’n’R model based on the DNS results (y+ = 0.1) it is a factor of 4 > the value in the original model based on Hall’s measurements of the lift force). This naturally has a significant effect of increasing the fraction resuspended for very short times (ωt ~< 1) iv and is the controlling influence over the entire range of times from short to long term resuspension. The second is the value of the ratio of the root-mean-square (rms) drag force to its mean value which in the modified model is nearly twice (1.8) than that in the original. This feature of the model is largely responsible for the greater fraction resuspended after times ~ 1s (times which are sufficient to include the transition period from short term resuspension to long term resuspension rates (~t-1). The third feature introduces changes in the resuspension because the distribution of aerodynamic drag forces in the modified model is distinctly non-Gaussian behaving more like a Rayleigh distribution. This means that the distribution of the drag force decays much more slowly in the wings of the distribution than the equivalent Gaussian (with the same rms) so that for very large values of the adhesive force / rms drag force ~ 8 (at the extreme end of the DNS measurements), the resuspension rate constant is a factor of 30 larger than that for an equivalent Gaussian model. Thus although the fraction of particles resuspended is very small in these instances, the differences between the modified and original models can be very large. This is particularly important when we consider resuspension from multilayer deposits. When we consider these influences in the context of a broad range of adhesive forces due to surface roughness, we find that in general, the modified model gives around 10% more for the fraction of particle resuspension fraction than the original R’n’R model (for an initial log normal distribution of adhesive forces), however the difference could become significant (3 to 7 times greater depending on the range of values of the adhesive-force spread factor) when the friction velocity is small (i.e., smaller resuspension fraction). As for the short-term resuspension rate, the difference between the modified and original model becomes significant when this is dominated by the typical forcing frequency (ω+ is 0.0413 for the original model, 0.08553 for LES approach and 0.127143 for DNS for y+ = 6). The sensitivity to the adhesive-force spread factor has also been studied and the results indicate that the modified model removes particles much more easily than the original model in conditions of small friction velocity and a smoother surface (i.e., small spread factor). Finally in this phase of the work, the correlation between the distribution of the fluctuating force and its derivative has been checked for both LES and DNS statistics. The results demonstrate that this correlation has a very slight effect on particle resuspension compared with the result from the uncorrelated curve-fitted model. In view of recent numerical data for lift and drag forces in turbulent boundary layers (Lee & Balachandar), the lift and drag we have considered and the impact of these data on predictions made by the non-Gaussian R’n’R model are compared with those based on O’Neill formula. The results indicate that, in terms of the long-term resuspension fraction, the difference is minor. It is concluded that as the particle size decreases the L&B method will lead to less-and-less long-term resuspension. Finally the ultimate model that has been developed in this work is a hybrid version of the R’n’R model adapted for application to multilayer deposits based on the Friess and Yadigaroglu multilayer v approach. The deposit is modelled in several overlying layers where the coverage effect (masking) of the deposit layers has been studied; in the first instance a monodisperse deposit with a coverage ratio factor was modelled where this was subsequently replaced by the more general case of a polydisperse deposit with a particle size distribution. The results indicate that, in general, as the number of modelled layers increases the resuspension fraction of the whole deposit after a certain time decreases significantly. In other words, it takes a much longer time to resuspend a thicker deposit. Taking account of the particle size distribution slightly increases the short-term resuspension. However, this change decreases the long-term resuspension significantly. The model results have been compared with data from the STORM SR11 test (ISP-40) and the BISE experiments. In general, both comparisons indicate that with smaller spread of the adhesive force distribution (i.e., the range of adhesive force distribution is narrower) the new multilayer model agrees very well with the experimental data. It can be inferred that multilayer deposits lead to much narrower distributions of adhesive force.

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33

Richardson, G. A. "Algebraic stress modelling for shock-wave/turbulent boundary-layer interactions." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267213.

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34

Silva, Freire Atila P. "An asymptotic approach for shock-wave/turbulent boundary layer interactions." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330307.

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35

Leung, Andrew Wing Che. "An investigation of three-dimensional shockwave/turbulent-boundary layer interaction." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284191.

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36

Siddons, J. T. "The vertical distribution of phytoplankton in a turbulent boundary layer." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3018308/.

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37

Barrantes, Analía Inés. "Turbulent boundary layer flow over two-dimensional bottom roughness elements." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42585.

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38

Rathnasingham, Ruben. "System identification and active control of a turbulent boundary layer." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10468.

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39

Musgrave, Patrick Francis. "Turbulent Boundary Layer over a Piezoelectrically Excited Traveling Wave Surface." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/97011.

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Recent studies have utilized spanwise traveling waves to alter the turbulent boundary layer with the aim of reducing skin friction drag. Spanwise traveling waves are a promising active drag reduction technique; however, the wave generation methods used in previous studies are bulky and could not be practically implemented. This research has developed an implementable traveling wave generation method and then fundamentally demonstrated how it changes the turbulent boundary layer, which is in a manner consistent with skin friction/shear stress reduction. Traveling waves were generated on a two-dimensional surface using low-profile piezoelectric actuators, in an open-loop fashion, and with minimal frequency limitations. The wave generation method was developed to generate tailored traveling wave patterns; thus, yielding control over the propagation direction, number of wave-fronts, and regions of the surface containing traveling waves. These tailored traveling waves have the capacity not just for affecting the boundary layer, but also for other applications such as propulsion. The implementable traveling wave generation method was then tested in a low-speed wind tunnel and shown to alter the structure of the turbulent boundary layer. The boundary layer is pushed off the wall, and the viscous sublayer is thickened, indicating a reduction in shear stress. Analysis of the boundary layer at positions phase-locked to the wave oscillation suggests that the traveling waves induce a phase-lag effect in the flow. This phase-lag produces a stretching of the viscous sublayer and may contribute to the skin friction reduction. The effects of standing waves on the turbulent boundary layer were also investigated and compared with traveling waves. The results indicate that both wave types alter the boundary layer in the same manner. Standing waves are simpler to generate than traveling waves, suggesting that standing waves may be an effective skin friction reduction method. Before traveling or standing waves can be implemented, further research is necessary to investigate the interaction between the wave pattern and the turbulent phenomena and also to quantify the skin friction reduction and overall net energy usage.
Ph. D.

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40

Sen, Mehmet Ali. "Proper Orthogonal Decomposition Methodology to Understand Underlying Physics of Rough-Wall Turbulent Boundary Layer." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SenMA2007.pdf.

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41

Ölçmen, Semih M. "An experimental study of a three-dimensional pressure-driven turbulent boundary layer /." This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06062008-172023/.

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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990.
Vita. Abstract. Two computer disks in pocket of volume. Includes bibliographical references (leaves 119-127). Also available via the Internet.

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42

Dasi, Lakshmi Prasad. "Statistical characteristics of turbulent chemical plumes." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21256.

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43

Coronado, Domenge Patricia X. "Delayed-Detached-Eddy Simulation of Shock Wave/Turbulent Boundary Layer Interaction." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/220.

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The purpose of this thesis is to study the shock/wave turbulent boundary layer interaction by using delayed-detached-eddy simulation (DDES) model with a low diffusion E-CUSP (LDE) scheme with fifth-order WENO scheme. The results show that DDES simulation provides improved results for the shock wave/turbulent boundary layer interaction compared to those of its predecessor the detached-eddy simulation (DES). The computation of mesh refinement indicates that the grid density has significant effects on the results of DES, while being resolved by applying DDES simulation. Spalart in 1997 developed the Detached-Eddy Simulation (DES) model, which is a hybrid RANS and LES method, to overcome the intensive CPU requirement from LES models. Near the solid surface within a wall boundary layer, the unsteady RANS model is realized. Away from the wall surface, the model automatically converts to LES. The Delayed-Detached-Eddy Simulation (DDES) was suggested by Spalart in 2006 to improve the DES model previously developed. The transition from the RANS model to LES in DES is not grid spacing independent, therefore a blending function is introduced to the recently developed DDES model to make the transition from RANS to LES grid spacing independent. The DDES is validated by computing a 3D subsonic flat plate turbulent boundary layer. The first case studied using DDES is a 3D transonic channel with shock/turbulent boundary layer interaction. It consists of two straight side walls, a straight top wall, and a varying shape in span-wise direction for a bottom wall. The second case studied consists of a 3D transonic inlet-diffuser. Both results are compared with experimental data. The computed results of the transonic channel agree well with experimental data.

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44

Diakoumakos, Elias. "Turbulent boundary layer with heat transfer and periodic free-stream velocity." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46745.

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45

Mitchell, G. "Interaction of a synthetic Jet with a thermal turbulent boundary layer." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492487.

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An experimental study has been performed to determine the influence of a synthetic jet on a thermal turbulent boundary layer. Measurements were carried out using a slot type synthetic jet operated in a water channel. PlV measurements were used to determine how the synthetic jet influenced the velocity field. Two formation methods of the synthetic jet were observed. At high jet to crossflow velocity ratios, the vortices produced by the jet move away from the wall, whereas at low velocity ratios they remain near the surface. As a result of the jet/crossflow interaction, there is a zone of reversed flow immediately downstream of the orifice accompanied by an increase in the velocity fluctuations. The velocity fluctuations decay with increasing distance downstream of the orifice. The magnitude of the velocity fluctuations decays with increasing distance downstream ofthe orifice. As part of a thermal study, LIF was used for temperature measurements of the fluid. During the expulsion cycle, the thermal boundary layer downstream of the orifice thickens, whereas during the suction cycle, the downstream thermal boundary layer is annihilated as it is entrained into the orifice. Hot-films connected to a constant current anemometer measured the plate temperature. The vortices produced by the synthetic jet sweep cool fluid towards the wall, reducing the surface temperature. Due to the oscillatory nature of the synthetic jet flow, the surface temperature fluctuates at the jet formation frequency. Finally, the synthetic was found to enhance the surface heat transfer. The gain in heat transfer is a result of increased mixing near the wall due to interaction of the synthetic jet with the boundary layer. A more powerful synthetic jet provides greater improvement in the average heat transfer. As the power of the synthetic jet increases, the efficiency ofthe jet at improving heat transfer reduces.

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46

Hood, Innes William. "Turbulent natural convection coupled with thermal radiation in a boundary layer." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27887.

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Turbulent natural convection coupled with thermal radiation in an absorbing gas, adjacent to a vertical heated plate has been studied. The results of a simplified theoretical model are compared with experimental data obtained using a heated vertical plate in a carbon dioxide and nitrogen gas mixture. The theoretical model assumes a gray, optically thin, nonscattering and infinite gas adjacent to a black, isothermal plate. In addition, the Boussinesq approximation was applied, using the velocity and temperature profiles of Eckert and Jackson. The momentum and energy equations were solved by an integral technique, with the radiation term modelled by two different methods: the mean beam length method; and an exponential kernal approximation. The experimental work consisted of obtaining the temperature and velocity profiles of a turbulent natural boundary layer at one location over a range of carbon dioxide and nitrogen gas compositions, and calculating and comparing the enthalpy flux for the different cases. Results are given in terms of a combined convective and radiative Nusselt number as a function of gas absorptivity. It was found that Eckert and Jackson's velocity profile did not predict the flow accurately. By modifying the profile to fit the data, good ageement between the theory and experiment was obtained.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

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47

Gagné, Jean-François. "An improved method for modelling fully rough turbulent boundary layer flows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq36888.pdf.

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48

Mahmoudnejad, Niloufar. "Numerical simulation of wall-pressure fluctuations due to turbulent boundary layer." Diss., Wichita State University, 2011. http://hdl.handle.net/10057/5151.

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Pressure fluctuations associated with turbulent boundary layer have been a prominent issue over the past few decades. In order to simulate pressure fluctuations beneath a turbulent boundary layer, a numerical investigation was performed in the current study. Four different turbulence models were employed to calculate the pressure and velocity fluctuations. A new approach of direct numerical simulation (DNS) was developed, as well. The proposed DNS scheme was hybrid of sixth-order weighted compact scheme (WCS) and modified weighted essentially non-oscillatory (WENO) scheme, which is called modified WENO-WCS scheme (MWWS) hereafter. A variety of benchmark problems were investigated to evaluate the accuracy of the proposed numerical scheme. Several empirical/semi-empirical mean square pressure models and single-point wall-pressure spectrum models were investigated to compare mean square wall pressure values. Reynolds-averaged Navier-Stokes based on Spalart-Allmaras (RANS-SA) and Delayed detached-eddy simulation based on Spalart-Allmaras (DDES-SA) turbulence models showed agreement with the Lowson, Lilley and Hodgson, and Goody models. Shear stress transport (RANS-SST) and DDES-SST models showed agreement with the Lowson, Farabee and Casarella, Lilley and Hodgson, and Goody models. The MWWS scheme was in agreement with Lowson and Goody models. Five single-point wall-pressure spectrum models were investigated and compared with numerical results. In low frequency region, results obtained by DDES-SA model and MWWS scheme were in agreement with the Goody model, while RANS-SA, RANS-SST, and DDES-SST turbulence models showed agreement with the Robertson model. In High frequency region, all investigated numerical methods were in agreement with the Goody and Efimtsov (1) models.
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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49

Pilatis, N. "Turbulent boundary layer prediction in three-dimensional ducts with core vorticity." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376873.

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50

Stretch, D. D. "The dispersion of slightly dense contaminants in a turbulent boundary layer." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377257.

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Дисертації з теми "Turbulent Boundary Layer (TBL)"

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