Flat-shaped Nose Design Optimization for Low-boom Supersonic Transport Configuration

The intense sonic boom generated by supersonic transport (SST) remains a significant obstacle for commercial supersonic flight. One crucial and sensitive factor influencing the intensity of sonic booms is the bow shock, which is closely related to the nose design of an SST. A flat-shaped nose can be applied to generate a multi-stage bow shock signature on the ground, thereby reducing sonic boom intensity. However, the underlying mechanism of mitigating sonic booms was not fully understood. This paper presents a flat-shaped nose design optimization, aimed at minimizing on-track ground loudness for a large-sized SST. The evolutionary process of the shock system and the formation of bow shock are analyzed. The sonic boom mitigation mechanism by employing a flat-shaped nose is then revealed. Results show that a strong nose shock followed by an extensive expansion wave is generated by a flat-shaped nose, with the expansion wave playing a crucial role in preventing shock coalescence during propagation. Consequently, a multi-stage bow shock is formed under both on-track and certain off-track conditions. For the configuration studied, the application of a flat-shaped nose results in a reduction of ground loudness of 3.68 PLdB on-track and an average of 2.33 PLdB across the full carpet.