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 current research interest is in the mixing enhancement. In the first part of the present study, 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 waves, named as class A and class B supersonic instability waves, can be identified. In addition to unstable waves, two families of neutral waves, named as class C and class D 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. As such they are very relevant to the supersonic combustion problem. The second part of the study explores the possibility of enhancing the rate of supersonic mixing by means of a periodic Mach wave system. The Mach wave system may be generated by small amplitude waviness of the confining channel walls. 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. / Source: Dissertation Abstracts International, Volume: 51-05, Section: B, page: 2446. / Major Professor: Christopher K. W. Tam. / Thesis (Ph.D.)--The Florida State University, 1990.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_78257 |
| Contributors | Hu, Fang Qiang., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 130 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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