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Numerical analysis of O3 depletions by exhaust plume from stratospheric flight at the altitude of 25km was conducted. Expanding box method was employed to simulate a diffusion of exhaust plume in the stratosphere. Concentrations of chemical species and normarized sensitivities of O3 concentration for reactions were estimated by fifth-order BDF method. Chemical kinetics include NOx, HOx and Ox chemistry. As results, it takes over two days that O3 concentration within a plume becomes ambient lebel within 1ppb. O3 perturbations were changed by an effect of plume-emission time, and they are bigger in daytime than in nighttime. Distributions of sensitivities of O3 concentrations for reactions are also changed for the plume-emission time. O3 depletion is greater by NOx than by HOx in exhaust plume.

Instability of a curved compressible shear layer was investigated by the use of linear stability analysis. If velocity of flow along a convex wall is larger than that of flow along a concave wall, flow field is unstable to purely spanwise disturbances and streamwise vortices are formed. Effects of parameters such as convective Mach number, velocity ratio and density ratio on growth rates were investigated. There are negligible effects of compressibility on growth rates of these disturbances, which indicates relatively effective mixing enhancement for flow fields where effects of compressibility is large. Study on viscous fluid showed that growth rates of spanwise disturbances with large wavenumber decrease in comparison to the case of inviscid fluid. As a result, a certain spanwise wavelength having maximum growth rates exists and control of wavelength can contribute to mixing enhancement.

Effects of solid wall on instability of a supersonic shear layer were investigated with the viewpoint of linear stability analysis. It is known that Mach waves become to be radiated from shear layers, as flow Mach number increases. In this case, because closed lower pressure regions of pressure perturbation, which grows to be core of vortex, cannot be formed in the shear layers, growth rates of disturbances are decreased extremely. In the present study, solid wall was set parallel to a supersonic shear layer. It is shown that, with the solid wall, outgoing Mach waves are reflected and turn back to the supersonic shear layer. The outgoing and incoming Mach waves form standing waves, and closed lower pressure regions are formed in the supersonic shear layer. It is shown that, with the solid wall, growth rates of disturbances are increased compared with that for without the solid wall.