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13.12 exhibits a round-tip bullet with a detached shock. The distance of the detachment is determined to a large degree by the upstream Mach number. The zone A is zone where the flow must be subsonic because at the body the velocity must be zero (the no-slip condition). In such a case, the gas must go through a shock. While at zone C the flow must be supersonic. The weak oblique shock is predicted to flow around the cone. The flow in zone A has to go through some acceleration to became supersonic flow. The explanation to such a phenomenon is above the level of this book (where is the ``throat'' area question13.25. Yet, it can be explained as the subsonic is ``sucked'' into gas in zone C. Regardless of the explanation, these calculations can be summarized by the flowing equation
where is a function of the upstream Mach number which tabulated in the literature.
The constant and the function are different for different geometries. As a general rule, the increase in the upstream Mach results in a decrease of the detachment distance. Larger shock results in a smaller detachment distance, or, alternatively, the flow becomes ``blinder'' to obstacles. Thus, this phenomenon has a larger impact for a relatively smaller supersonic flow.
Next: Issues Related to the Up: Oblique Shock Previous: Maximum Value of Oblique Index Created by:Genick Bar-Meir, Ph.D.
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