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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 23 for “"pressure spectra"”.
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Investigation of the baroreflex of the rat : steady state and dynamic features
… feedback systems in the body to maintain blood pressure variation within the homeostatic range. In this dissertation, the important features of the carotid and aortic baroreflexes have been extensively investigated on ventilated, central nervous system intact, neuromuscular blocked (NMB) rats …
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The Wall Pressure Spectrum of High Reynolds Number Rough-Wall Turbulent Boundary Layers
… layer and the generation of a fluctuating pressure field imposed on the surface. While numerous studies have investigated the wall pressure fluctuations over zero-pressure gradient smooth walls, few studies have examined the effects of surface roughness on the wall pressure field. …
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The Effects of Pressure Gradient and Roughness on Pressure Fluctuations Beneath High Reynolds Number Boundary Layers
… family of continually varying, bi-directional pressure gradient distributions are investigated in both wind tunnel experiments and steady 2D and 3D Reynolds Averaged-Navier-Stokes (RANS) computations. The effects of pressure gradient, pressure gradient history, roughness, combined roughness and …
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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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Ice-Induced Unsteady Flowfield Effects on Airfoil Performance
… were presumed to be the cause of large-scale pressure fluctuations upstream of reattachment at small angles of attack. Pressure spectra near reattachment exhibited wide bandwidth frequency peaks that indicated a non-periodic phenomenon and corresponded to the regular mode often associated with …
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Statistical Scaling of Turbulent Surface Pressure in the Atmospheric Boundary Layer
… the atmosphere produces fluctuations in static pressure through a variety of mechanisms. These fluctuations are of interest both to atmospheric scientists, as a fluid dynamic property, and to acousticians, as a source of wind noise. At the ground surface, previous work has found the dominant …
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Simulation of fluctuating wind pressures on low building roofs
Wind pressure fluctuations acting on low building roofs are important for the prediction of peak pressure values and for fatigue design purposes. Collection of several time histories of pressure fluctuations, using traditional wind tunnel measurements is time consuming and expensive. Within this …
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Experimental measurement of combustion noise and comparison to a predictive model
… The data are presented in the form of acoustic pressure spectra and over-all sound pressure levels. The experiment consisted of a geometrically simple pre-mixed burner with five interchangeable nozzles whose diameters varied from 0.117 cm to 0.541 cm. The fuels examined in the experiment were …
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Wall Jet Boundary Layer Flows Over Smooth and Rough Surfaces
The aerodynamic flow and fluctuating surface pressure of a plane, turbulent, two-dimensional wall jet flow into still air over smooth and rough surfaces has been investigated in a recently constructed wall jet wind tunnel testing facility. The facility has been shown to produce a wall jet flow with …
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A Study of Bio-Inspired Canopies for the Reduction of Roughness Noise
… was used to perform far-field noise and surface pressure fluctuation measurements in the presence of various combinations of rough surfaces and suspended canopies. All canopies were demonstrated to have a strong influence on the surface pressure spectra, and attenuations of up to 30 dB were …
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The Effect of Composition on the High-Pressure Behavior of Rare-Earth Phosphate Minerals
… are isostructural with xenotime (I41/amd). Raman spectra are consistent with previous studies and high-pressure spectra showed no phase transitions up to 10 GPa under hydrostatic conditions. The spectra were used to develop Kieffer-type lattice vibrational models to calculate heat capacities of …
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The characterization of the flowfield of a dump combustor
… stable mode. Stability was identified by the pressure spectra obtained under various running conditions using piezoelectric pressure transducers wired to a spectrum analyzer. Operational parameters such as fuel composition, fuel injection location, acoustic configuration, and equivalence ratio …
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Pressure Shielding Mechanisms in Bio-Inspired Unidirectional Canopy Surface Treatments
Reduction of surface pressure fluctuations is desirable in various aerodynamic and hydrodynamic applications. Over the past few years, studies on canopy surface treatments have been conducted to investigate the fundamental mechanisms of surface pressure attenuation termed as pressure shielding. …
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An experimental study of flow over a 6 to 1 prolate spheroid at incidence
… transition. Forces and moments tests, surface pressure distribution measurements as well as the surface presure fluctuations, and mini-tuft flow visualization tests were made to document the flow characteristics on the surface of the body with an artificial boundary layer trip. It was found …
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Broadband Noise Prediction of an Axial Compressor Operating at Low Reynolds Number
… was needed for convergence of velocity and pressure spectra describing acoustic sources, a relatively coarse LES could still provide similar estimates of second order statistics such as Reynolds stresses. When compared to experiment, the LES results show a pleasing ability to accurately …
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Pressure Fluctuations in a High-Reynolds-Number Turbulent Boundary Layer over Rough Surfaces of Different Configurations
The pressure fluctuations under a high Reynolds Number, rough-wall, turbulent, boundary layer have been studied in the Virginia Tech Stability Wind Tunnel. Rough surfaces of varying element height (1-mm, 3-mm), shape (hemispheres, cylinders) and spacing (5.5-mm, 10.4-mm, 16.5-mm) were investigated …
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The far-infrared absorption spectrum of low temperature hydrogen gas
… pm), over the temperature range 21-38 K, and the pressure range0.6-3 atmospheres. The spectra cover the very weak and broad collision-induced translational absorption band of 112 which at these low temperatures is observed well isolated from the 112 rotational lines. Translational absorption …
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A study on flow development in an APU-style inlet and its effect on centrifugal compressor performance
… steadiness was achieved by tuning the pressure controller using a PID control method and utilizing multi-layer screens downstream of the APU inlet. Less than 1% relative unsteadiness was achieved for full range operation.</p> <p>The flow field inside the rectangular-sectioned 90? bend …
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Mathematical Modelling of Acoustic Diffraction Noise Embracing Diverse Boundary Conditions
… the incident gust to its far-field scattered pressure. We sum the solutions for all possible eddies using a turbulence spectrum that associates each eddy with its expected energy and length scales. This approach is valid for both leading and trailing-edge noise models. Slight changes in …
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The Space-time Structure of an Axisymmetric Turbulent Boundary Layer Ingested by a Rotor
… turbulent boundary layer under a strong adverse pressure gradient is experimentally studied for its relevance to marine applications, urban air-transportation and turbulence ingestion noise. The combined effect of lateral curvature and streamwise pressure gradient are examined on the mean flow, …
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