![]() Moreover, static firing tests are expensive to conduct. Hence, the model proposed in NASA SP-8072 is not suitable as a design tool for new launch pads. Therefore, it is necessary to create a model to modify the prediction results for each launch pad. ![]() The method proposed in NASA SP-8072 is based on a large amount of flight data and the result of static firing tests that were conducted by the organization in the United States it does not consider the effects of the launch pad and the facility because the model proposed in NASA SP-8072 assumes that sound sources are distributed along a jet path. ![]() 2 performed a static firing test of 1:42 scale booster in order to investigate the effects of launch pad shape on the acoustic level. Traditionally, the acoustic level has been predicted by means such as a semi empirical method proposed in NASA SP-8072 by Eldred 1 or subscale tests. Therefore, prediction and reduction of the acoustic level at the lift off are necessary. The acoustic waves reflect from the ground surface and the launch facility, causing the vibration of the payload in the fairing. In particular, the exhaust gas from a rocket engine generates strong acoustic waves. The calculation shows the following yields: (1) unsteady fluctuation of hydrodynamic forces become smaller as the Mach number increases under the same Reynolds number condition, (2) the drag coefficient increases with the Mach number due to an increase in the pressure drag by the shock wave, and (3) an accurate prediction of the drag coefficient in the supersonic regime using traditional models might be difficult.Ĭertain acoustic phenomena are caused by fluid behavior. The analysis is conducted by assuming a rigid sphere with a Reynolds number of between 50 and 300, based on the diameter of the sphere and the freestream velocity and a freestream Mach number of between 0.3 and 2.0, together with the adiabatic wall boundary condition. The calculation is performed on a boundary-fitted coordinate system with a high-order scheme of sufficient accuracy. In this study, analysis of flow properties around a sphere and its aerodynamic coefficients in the high-Mach-and-low-Reynolds-numbers conditions is carried out by direct numerical simulations solving the three-dimensional compressible Navier–Stokes equations. ![]()
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