2014 年 62 巻 3 号 p. 77-84
This paper describes the effectiveness of the direct simulation for the sonic boom prediction over the whole computational domain from the body to the ground and the nature of the sonic boom propagation for the hypersonic vehicle. Both the near and far fields around an axi-symmetric paraboloid are numerically obtained by the axi-symmetric Euler analyses assuming the uniform atmosphere. Moreover, the three dimensional Euler analyses with the gravity term have been conducted to consider the variation of the atmospheric properties with the altitude. Consequently, it is confirmed that the direct simulations are the same level of accuracies of waveform parameter method. Furthermore, the nature of the sonic boom propagation does not change up to Mach 7 in the uniform atmosphere and Mach 5 in the real atmosphere, when the small disturbance is assumed. Therefore, the evaluation method for the sonic boom propagation at the supersonic speed is applicable to predict the sonic boom strength at the hypersonic speed. At the ground level, the sonic boom intensity generated by the Mach 5 flight at 25km altitude is less than the intensity by the Mach 2 flight at 15km altitude.