Abstract:

High fidelity sonic boom prediction and low sonic boom design method is one of the key technologies of next generation environment-friendly supersonic aircraft which has a direct bearing on the feasibility of commercial operation and operation economics.This paper developes a high fidelity sonic boom prediction method based on computational fluid dynamic (CFD), the wave form parameter method and the MARK-VII method. The design of a quiet spike is studied by using the high fidelity sonic boom prediction method. It is found that the critical length of the quiet spike is important. If the length of a quiet spike is shorter than its critical length, the shock wave of the spike will coalesce with the nose shock, which can lead to invalidation of the quiet spike. On the other hand, if the length of the spike is longer than the critical length, the sonic boom will increase too. The critical length of a quiet spike varies with the flight altitude and flight Mach number; therefore the length of a quiet spike changes with flight condition. Multi-order quiet spikes can produce multi-weak shocks to replace the strong nose shock, which can suppress the sonic boom level more effectively. At the same time, the length of each order of spike should be equal to the critical length. Different nose shapes of a quiet spike can produce different detached shocks and shock detachment distances, which can lead to different drag coefficients and temperatures. But the influence of nose shape on far field sonic boom is not obvious. The sonic boom of the quiet spike layout is lower than the original layout, but the drag coefficient is slightly increased.

Key words: supersonic aircraft, shock wave, computational fluid dynamics, acoustic wave propagation, aerodynamic noise