skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Confined supersonic mixing layers: A computational investigation of instability and mixing enhancement

Abstract

Hydrodynamic instability of a compressible shear mixing layer plays a very important role in controlling and promoting the mixing processes in supersonic combustion problems. At supersonic convective Mach numbers, the natural mixing rates of the shear layer are observed to be very small. The linear spatial instability problem of a supersonic shear mixing layer inside a rectangular channel is solved. A systematic way of calculating and classifying all the normal modes is developed. It is demonstrated that a vortex sheet at high supersonic convective Mach number, neutrally stable when unconfined, becomes unstable when confined. Extensive numerical computations indicate that two classes of unstable supersonic instability waves can be identified. In addition to unstable waves, two families of neutral acoustic waves can also be identified. The characteristics of the unstable waves as well as the neutral waves are determined. It is concluded that the new supersonic instabilities found in this study are the dominant instabilities of a confined mixing layer at high supersonic convective Mach numbers. Thus, they are very relevant to the supersonic combustion problem. The possibility of enhancing the rate of supersonic mixing by means of a periodic Mach wave system is explored. The stability of the periodic basicmore » flow is analyzed numerically by the Floquet theory and the spectral-collocation method. The convergence of the numerical solutions is discussed. New secondary instabilities of the shear layer induced by the periodic Mach waves are found computationally. The growth rate of the new instabilities is found to vary nearly linearly with the ratio of the wavy wall amplitude to the wave length. Therefore, it is a potentially promising scheme for the enhancement of supersonic mixing.« less

Authors:
Publication Date:
Research Org.:
Florida State Univ., Tallahassee, FL (USA)
OSTI Identifier:
5894863
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Ph.D. Thesis
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMBUSTION KINETICS; SUPERSONIC FLOW; COMPRESSIBLE FLOW; CONFINEMENT; LAYERS; MACH NUMBER; MIXING; SOUND WAVES; STABILITY; CHEMICAL REACTION KINETICS; FLUID FLOW; KINETICS; REACTION KINETICS; VELOCITY; 400800* - Combustion, Pyrolysis, & High-Temperature Chemistry

Citation Formats

Hu, F Q. Confined supersonic mixing layers: A computational investigation of instability and mixing enhancement. United States: N. p., 1990. Web.
Hu, F Q. Confined supersonic mixing layers: A computational investigation of instability and mixing enhancement. United States.
Hu, F Q. Mon . "Confined supersonic mixing layers: A computational investigation of instability and mixing enhancement". United States.
@article{osti_5894863,
title = {Confined supersonic mixing layers: A computational investigation of instability and mixing enhancement},
author = {Hu, F Q},
abstractNote = {Hydrodynamic instability of a compressible shear mixing layer plays a very important role in controlling and promoting the mixing processes in supersonic combustion problems. At supersonic convective Mach numbers, the natural mixing rates of the shear layer are observed to be very small. The linear spatial instability problem of a supersonic shear mixing layer inside a rectangular channel is solved. A systematic way of calculating and classifying all the normal modes is developed. It is demonstrated that a vortex sheet at high supersonic convective Mach number, neutrally stable when unconfined, becomes unstable when confined. Extensive numerical computations indicate that two classes of unstable supersonic instability waves can be identified. In addition to unstable waves, two families of neutral acoustic waves can also be identified. The characteristics of the unstable waves as well as the neutral waves are determined. It is concluded that the new supersonic instabilities found in this study are the dominant instabilities of a confined mixing layer at high supersonic convective Mach numbers. Thus, they are very relevant to the supersonic combustion problem. The possibility of enhancing the rate of supersonic mixing by means of a periodic Mach wave system is explored. The stability of the periodic basic flow is analyzed numerically by the Floquet theory and the spectral-collocation method. The convergence of the numerical solutions is discussed. New secondary instabilities of the shear layer induced by the periodic Mach waves are found computationally. The growth rate of the new instabilities is found to vary nearly linearly with the ratio of the wavy wall amplitude to the wave length. Therefore, it is a potentially promising scheme for the enhancement of supersonic mixing.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1990},
month = {1}
}

Miscellaneous:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that may hold this item.

Save / Share: