Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 33 for “"zero-pressure gradient"”.
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Net Flow Through Soft Porous Media Generated by a Periodic Mean-Zero Pressure Gradient
… investigate the effect of applying periodic mean-zero pressure gradients to a soft porous medium. These periodic mean-zero pressure gradients are composed of square waves, with a high magnitude positive pressure drop applied for 1/3 of the period and a negative pressure drop with half the …
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Flat plate turbulent boundary layer static temperature distribution with heat transfer
… static temperature-velocity distribution for a zero pressure gradient turbulent boundary layer is derived based on the differential equations for local heat transfer and shear. The present theoretical method of computation is found to give results that correspond well with available experimental …
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Investigation of turbulent boundary layer structure using particle image velocimetry
… fields in the streamwise wall-normal plane of a zero-pressure-gradient turbulent boundary layer. In total, 340 PIV realizations of the boundary layer were obtained at Reynolds numbers based on momentum thickness of Ree = 930, 2370 and 6845. Each realization contains approximately 10000 …
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Numerical Simulation of Vortex Generating Jets in Zero and Adverse Pressure Gradients
… steady blowing of angled jets, subjected to a zero pressure gradient, yielded excellent agreement with the PIV data in terms of vortex formation and strength. Observed flow features include primary and secondary vortices, where the primary vortex eventually dominates the downstream region. A …
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Some unsteady features of turbulent boundary layers
For steady free-stream, zero and favorable pressure gradient turbulent boundary layers, the unsteadiness in the form of turbulent fluctuations was investigated. Phase ensemble-averaged flow characteristics of a large amplitude periodic unsteady turbulent boundary layer was also investigated at a …
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Statistical Analysis of High-Order Moments from Direct Numerical Simulation of a Turbulent Boundary Layer
High-order zero-pressure-gradient turbulent boundary layer statistics are important for turbulence modeling efforts and insight into the nature of turbulent flow. In this thesis, a complete database of third-, fourth-, and fifth-order central velocity moments is presented. The statistics were …
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Wall-modeled Large-eddy Simulation Based on Building-block Flows
… flows. The model is constructed to predict zero-pressure-gradient wall-bounded turbulence, adverse/ favorable pressure gradient effects, separation and laminar flow. The approach is implemented using a Bayesian classifier, which identifies the contribution of each building block in the flow, …
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An Experimental Study of Longitudinally Embedded Vortices in a Turbulent Boundary Layer via the Non-Invasive Comprehensive LDV Technique
… quantities resulting from vortices embedded in a zero pressure gradient turbulent boundary layer. Turbulent boundary layers are found in most flow regimes over large scale vehicles and have been studied for many years. Various systems to control separation of boundary layers have been proposed, …
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Near-wall similarity in two- and three-dimensional turbulent boundary layers
Static pressure, mean velocity, indirect wall shear from Preston tubes, direct wall shear using a two-dimensional (single line of action) floating element device, and direct wall shear measurements from an omnidirectional floating element capable of simultaneously determining magnitude and …
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Experimental Investigations into Shark Skin Inspired Active Flow Control Mechanisms
… smoothplate case. In the first set of tests, a zero pressure gradient case, it was found that the actuation of the flaps increased the overall momentum in the boundary layer near the wall,when compared to the flat plate case. This momentum increase helps support the hypothesis that the flexible …
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A study of the large-scale structure in a supersonic slot injected flow field
… length of the turbulent structures. A zero pressure gradient supersonic boundary layer was studied upstream of the slot injection, and results were compared with previously published data. Structure angles on the order of 50° were obtained throughout the majority of the boundary layer, …
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Verification of Statistical Turbulence Models in Aerodynamic Flows
… CFL3D and FUN3D. The benchmark cases are the zero pressure gradient boundary layer of flow over a flat plate and a two-dimensional bump in a channel. A number of flow profiles obtained with NASAs definitions of 'standard' versions of the Spalart-Allmaras, Shear Stress Transport, and k-\u03c9 …
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The Rough Wall High Reynolds Number Turbulent Boundary Layer Surface Pressure Spectrum
… very few studies investigating the rough wall pressure spectra under fully rough flows, which are relevant to many common engineering applications operating within this regime. This investigation uses the Virginia Tech Stability Wind Tunnel to perform experiments on a series of high Reynolds …
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Turbulent Boundary Layer Flow Over a Bump
… While two-dimensional (2D) TBLs under zero-pressure-gradient (ZPG) conditions are well understood, real-world boundary layers often experience complex three-dimensional (3D) effects due to surface curvature and pressure gradients. These conditions introduce flow skewing, anisotropy, and …
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Large-eddy simulation of turbulent wall-pressure fluctuations using the finite element method
In the present dissertation, turbulent wall-pressure fluctuations are characterized. To capture the turbulent characteristics of the flow, large-eddy simulation is used to resolve the large scale motions of the flow directly. A wall-adapting local eddy-viscosity model is selected to account for …
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Transition in boundary layer flows
… influence of freestream turbulence and pressure gradient upon transition within a boundary layer developing on a flat plate is elucidated by a series of controlled experiments.<br/><br/>From the data accumulated, the concept of statistical similarity in transition regions is extended to …
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Turbulent Boundary Layers over Rough Surfaces: Large Structure Velocity Scaling and Driver Implications for Acoustic Metamaterials
… of controlling acoustic waves driven by pressure fluctuations from flow. A turbulent boundary layer scaling analysis was performed on zero-pressure-gradient turbulent boundary layers over rough surfaces, for 30,000≤〖Re〗_θ≤100,000. Relationships between fluctuating pressures and velocities …
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Structure of Turbulent Boundary Layers and Surface Pressure Fluctuations on a Patch of Large Roughness Elements
Measurements were made in a zero pressure gradient turbulent boundary layer over two roughness patches containing hemispherical and cubical elements. The elements were 3 mm in height and spaced 16.5 mm apart in an array containing 7 streamwise rows and 6 spanwise columns for a total of 42 elements …
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An Experimental Study of Turbulent Boundary Layers Subjected to High Free-stream Turbulence Effects
… two-dimensional turbulent boundary layers at zero pressure gradient subjected to high free-stream turbulent intensities of up to 7.9% in preparations for high free-stream turbulence studies on three-dimensional boundary layers, which will be done in the future in the Aerospace and Ocean …
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Fluid Dynamics and Surface Pressure Fluctuations of Turbulent Boundary Layers Over Sparse Roughness
… have been performed on a two-dimensional zero pressure gradient turbulent boundary layer over sparsely spaced hemispherical roughness elements of 2 mm diameter. Laser Doppler velocimetry was used to measure all three components of velocity. The friction velocity was calculated using an …
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