ANALYSIS OF AXISYMMETRICAL SHOCK FOCUSING PHENOMENONS BY FLOW VIZUALIZATION,MEASURMENTS OF PRESSURE AND DENSITY AND NUMERICAL CALCULATIONS

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Computational and experimental studies of focusing of shock wave reflected from an axisymmetrical parabolic wall were conducted. The shadowgraph fo a focusing shock wave were optically visualized in the shock tube experiments and compared with the computer shadowgraphs which was developed based on the principle of optical shadowgraph. The comparison gives a fairly good agreement. The gasdynamic focus determined by optical shadowgraphs almost agree with the calculated ones.It is seen from the comparison of the computations and experiments, that the measurement of pressure history at the bottom of the reflector supports the numerical simulation. Furthermore, numerical studies of focusing process with vibrationally excitated case have been performed. The results show that the vibrational relaxation plays an important role for the shok focusing phenomena and the gasdynamic focus defined as the maximum pressure position dose not appear in the case of incident shock Mach numbers lager than 5.