Sonic Boom Assessment of a Hypersonic Transport Vehicle with Advanced Numerical Methods

摘要

Sonic boom is one of the major aspect to be considered in the development of a hypersonic civil aircraft concept. A possible solution to compute the level of sonic boom at the ground is to use a multi-layer propagation strategy combining different solvers for each step of the propagation from the aircraft to the ground. Nevertheless, the main scientific and technical difficulties to predict this phenomenon are the near-field computations for high Mach numbers, the apparition of caustics and shadow zones at the ground and the influence of the atmospheric turbulence. The first layer is evaluated by computing the pressure field sufficiently far from the vehicle, using advanced CFD methods based on an automatic mesh refinement process. The pressure field obtained this way is extracted on a cylinder which is then used as an input for acoustic propagation by a state-of-the art ray tracing software. The propagation in the turbulent Planetary Boundary Layer is finally handled by an original numerical model. A nonlinear scalar wave equation taking into account diffraction, absorption, ground reflection, shock waves, mean stratified flow and three-dimensional turbulence is solved by means of a dedicated one-way high performance numerical solver. This one is used to quantify sonic boom penetration into the shadow zone for different turbulent intensities.