Investigations on Sonic Boom Mitigation Effect for Supersonic Transport Based on Quiet Spike

Sonic boom is one of the obstacles restricting the development of Supersonic Transport (SST). This work investigates the effect and law of Quiet Spike, one method of sonic boom passive mitigation. Based on JAXA Wing Body (JWB), the sonic boom mitigation effect of different lengths, diameters and stage numbers of Quiet Spike is studied by using CFD method in the near field and Augmented Burgers Equation method in the far field. Quiet Spike transforms the bow-shaped strong shock at the nose of JWB into multiple oblique shocks, which causes the secondary or multiple overpressure phenomenon in the far field. Single-stage Quiet Spike has critical length and critical diameter that can minimize sonic boom intensity, the mechanism and the law of which are explained briefly below: (a) short Quiet Spike yields a large initial overpressure, due to that its shock tends to be merged with the fuselage shock completely during the propagation; (b) long Quiet Spike leads to a large secondary overpressure, because its shock has little influence on the fuselage shock due to the distance; (c) thin Quiet Spike results in a large initial overpressure, as there is a strong shock at the Quiet Spike and fuselage joint; (d) thick Quiet Spike produces large initial and secondary overpressures at the same time, on account of that it causes a strong shock and has a limited effect on the fuselage shock due to the large shock angle; (e) it is calculated that the single-stage Quiet Spike of JWB has the critical length of 7.27 m and critical diameter of 400 mm. With the increasement of Mach number, the critical length of single-stage Quiet Spike increases at first and then decreases, presenting a design rule of cubic function. Multi-stage Quiet Spike produces multiple oblique shocks and causes the multiple overpressure phenomenon in the far field, mitigating sonic boom intensity further. The result can provide a guidance for the design of Quiet Spike of Supersonic Transport with practical significance.