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 35 for “"pressure fluctuation"”.
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Wall Features of Wing-Body Junctions: Towards Noise Reduction
… been found to generate regions of high surface pressure fluctuations and turbulence that are detrimental to structural components and acoustics. With the focus in the military and commercial industry on reducing the acoustical impact of aircraft and their engines, very little research has been …
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Some features of surface pressure fluctuations in turbulent boundary layers with zero and favorable pressure gradients
… are interested in the structure of the surface pressure fluctuations for the development and use of noise prediction techniques for helicopter and turbomachinery rotors. This study, conducted in the Virginia Tech low speed boundary layer wind tunnel, covered the effects of zero and favorable …
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On the Statistical Nature of Boiling Flows - an Experimental Approach
… were used. Two flow-field variables, viz. static pressure fluctuations at the test section outer wall and instantaneous chordal-average vapor fraction, were studied. Matched piezo-electric pressure transducers were used for the pressure fluctuation measurements, and a linearized dual-beam x-ray …
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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 integral …
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Fluid Dynamics and Surface Pressure Fluctuations of Two-Dimensional Turbulent Boundary Layers Over Densely Distributed Surface Roughness
Measurements were made in two-dimensional zero pressure gradient turbulent boundary layers over 5 geometries of three-dimensional densely distributed surface roughness. A 3-velocity component laser Doppler velocimeter was used to measure instantaneous velocities. These measurements permitted an …
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Investigation Of Pressure Fluctuations In The Hyporheic Zone In Response To Flow Around A Hydraulic Structure
… interface. This study maps hyporheic pressure fluctuations as they are related to surface water velocity. The pressure map is used to evaluate lift enhancement and destabilization forces on the riverbed. High pressure events in the subsurface help generate a destabilizing force from …
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Modelling of Wall Pressure Fluctuations Induced by Turbulent Boundary Layer Flow
… to predict the power spectral density of wall pressure fluctuations in the turbulent boundary layer. From the analysis of current semi-empirical models and a large survey of experimental data, it was found that the models proposed by Goody and Smol'yakov have the lowest mean squared error when …
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Preliminary experiment and analysis of supersonic inlet buzz
… the continuous shock oscillation and the static pressure fluctuation. The hypothesis based on internal pressure measurement and shadowgraph pictures during stable operations revealed the substantial influence of the separated flow inside the model. Possible increase in subsonic Mach number at the …
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Unsteady Turbulence Interaction in a Tip Leakage Flow Downstream of a Simulated Axial Compressor Rotor
… and time averaged 3-component turbulence and pressure fluctuation measurements. These measurements are made for tip gap from 0.83% to 3.3% chord and streamwise locations from 0.772% to 1.117% blade spacing axially downstream of the cascade. The phase averaged inflow measurements reveal that …
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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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High Reynolds Number Turbulent Boundary Layer Flow over Small Forward Facing Steps
… to 213,000. The measurements included mean wall pressure, single and 2 point wall pressure fluctuations, single and 2 point velocity fluctuations and, oil flow visualization. Pressure fluctuation measurements were made 5 boundary layer thicknesses upstream of step to 22 boundary layer thickness …
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Impact of vertical internals on the hydrodynamics and heat transfer coefficient in a gas-solid fluidized bed
… hydrodynamic characteristics, flow regime, pressure drop, and heat transfer in a 0.14 m inside diameter gas-solid fluidized bed column of. Two sizes of vertical internal tube bundles (0.0127 and 0.0254 m) of circular arrangement have been implemented to represent the heat exchange tubes …
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Bio-Inspired Trailing Edge Noise Control: Acoustic and Flow Measurements
… a single hot-wire probe, and surface pressure fluctuation microphones. The far-field noise results showed that each treatment successfully reduced the noise, by up to 7 dB in some cases. The surface pressure measurements showed that the spanwise coherence was slightly reduced when the …
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Dynamic Pressure Sensing for the Flight Test Data System
… data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module …
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Characterization of unsteady loading due to impeller-diffuser interaction in centrifugal compressors
… assessed by comparing results against unsteady pressure and velocity measurements in the vaneless space. Simulations are shown to be adequate for identifying the trends of unsteady impeller blade loading with operating and design parameters. However they are not sufficient for predicting the …
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Incompressible flow over a three-dimensional cavity
… of the spectral entropy and energy of the pressure fluctuation is used for predicting the location of transition in the shear-layer flow. Typical results of simulation of incompressible laminar flow past a rectangular cavity for a range of Reynolds numbers are presented. The results …
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Fatigue crack growth in hydrogen pipeline steels
… on the inner diameter surface due to hydrogen pressure fluctuation. This behavior is compared with the life of the line pipe in an inert environment (e.g. natural gas or N2) under the same pressure fluctuations. The hydrogen or the inert environment pressure history is analyzed with the …
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Geomechanical Stability Analysis for Co2 Sequestration in Carbonate Formation
… the mechanism of strain localization due to pore pressure fluctuation.</p><p>Based on these laboratory and numerical tests, it is concluded that two mechanisms are competing for rock failures in deep carbonate formations during CO2 sequestration. One is the faulting induced by pore-pressure …
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Fiber Optic Sensing of Strain and Temperature for Structures in a Hypersonic Flow
… of the plenum box, and the generated backpressure influenced the (acoustic) stiffness of the system. A variety of testing conditions were studied, and 19 experiments were conducted at Mach 6 flow speed. The following parameters were varied in the experiments: fin angle, plenum …
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Simulation of Flow in a Solid Fuel Ramjet Cavity
… Lc). The second is characterized with radial fluctuations in the mixing chamber and features the maximum chamber radius of the ramjet as its scaling length. Mixed (radial and axial) modes in the intermediate frequency range reveal the effect of a slanted aft wall on the acoustics. …
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