Cartesian Mesh Simulations for the Third AIAA Sonic Boom Prediction Workshop

Abstract

Simulation results are presented for all cases from the Third AIAA Sonic Boom Prediction Workshop. An inviscid, embedded-boundary Cartesian-mesh flow solver is used in conjunction with adjoint-based mesh adaptation to compute near-field pressure signatures. Specialized techniques are applied to maximize accuracy and minimize cost on Cartesian meshes. Regions of the flow most sensitive to discretization error are identified using Richardson extrapolation. Timing results and mesh sizes for near-field cases demonstrate that decomposition into multiple offtrack simulations is efficient in both computational time and wall-clock time, with results among the least computationally expensive of those presented at the workshop. Pressure signals are propagated to the ground using an augmented Burgers equation solver to predict boom carpets. Ground signatures and loudness metrics are presented for a standard atmosphere as well as an atmosphere with wind profiles that affect overall noise levels and can significantly widen the boom carpet. Mesh convergence studies show that high sampling frequencies, around 500 kHz, are required for on-track propagation; the sampling frequency increases at large off-track angles due to longer acoustic ray paths. Overall, the approach presented here yields accurate results for predicting low-sonic-boom signatures.