Interactions of isotropic and homogeneous turbulence with shock waves.
Item
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Title
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Interactions of isotropic and homogeneous turbulence with shock waves.
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Identifier
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AAI9618046
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identifier
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9618046
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Creator
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Briassulis, George Konstantinos.
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Contributor
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Adviser: Yiannis Andreopoulos
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Date
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1996
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Mechanical | Engineering, Aerospace
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Abstract
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An experimental study of the interaction of a normal shock wave with decaying grid generated turbulence has been performed using time resolved pressure, velocity, temperature and Mach number measurements in a shock tube. Spatial resolution of the order of 7-26 Kolmogorov viscous length scales was achieved in the measurements of turbulence. A variety of turbulence generating grids provide a wide range of turbulence scales with flow Mach numbers ranging from 0.3 to 0.7 and shock Mach numbers from 1.2 to 1.6.;Analysis of the acquired data revealed that the amplification of the pressure fluctuations after the interaction of the normal shock wave with the flowfield depend on the grid's mesh size (initial turbulence level) and shock strength. Furthermore, spectral analysis confirmed that there exists amplification in the wavenumbers after the interaction and this amplification is not constant for the whole range of wavenumbers resolved.;The present results verified a proposed power law decay of the turbulent Mach number M{dollar}\rm\sb{lcub}t{rcub}{dollar} in the range of 0.01 to 0.1. Mach number fluctuations were increased with increasing mean flow Mach number and decrease with coarser grid.;The dissipation rate of kinetic energy was found to decrease after the interaction while the dissipative, Taylor's microscale and Kolmogorov's length scale were found to increase. Integral length scales were found to substantially decrease through the interaction with the shock wave in all investigated cases. It appears that at the weakest of the present interactions the eddies are compressed in the longitudinal direction drastically while their extent in the normal direction remains relatively the same. As the shock strength increases the lateral length scale increases while the longitudinal decreases. At the strongest interaction of the present cases the eddies are compressed in both directions. The outcome of the interaction strongly depends on the initial conditions.;The present results clearly show that most of the changes, either attenuation or amplification occur at large x/M distances where the length scales of the incoming flows are large and turbulence intensities low. Thus large in size eddies with low velocity fluctuations are affected the most by the interaction with the shock.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
