Numerical and Mesh Resolution Requirements for Accurate Sonic Boom Prediction of Complete Aircraft Configurations

A careful study is conducted to assess the numerical mesh resolution requirements for the accurate computation of sonic boom ground signatures produced by complete aircraft configurations. The details of the ground signature can depend heavily on the accurate prediction of the pressure distribution in the near-field of the aircraft. It is, therefore, important to accurately describe the geometric details of complete configuration (including the wing, fuselage, nacelles, diverters, etc) and to precisely capture the propagation of shock and expansion waves at large distances from the aircraft. Unstructured, adaptive mesh technologies are are ideally suited for this purpose as they use mesh points only in the appropriate locations within the flow field. In this work, we consider a supersonic business jet (SBJ) configuration that was tested at the NASA Langley Research Center. Near-field data was measured at several locations underneath the flight track. The propagation of these near-field signatures from different altitudes can be shown to result in near N-wave ground booms. In order to examine the effect of both nacelles and empennage, results for three test cases are presented. These test cases represent the complete configuration, the configuration without the nacelles, and the configuration without the nacelles and empennage. Inviscid solution adaptive unstructured meshes with up to 7.2 million nodes and 42.1 million tetrahedra are used to calculate the pressure distributions at several locations below each configuration where comparisons with experimental data are performed. All near-field pressure distributions are propagated to the ground (from an altitude of 50,000 ft) to predict the ground boom and the perceived noise level of the ground signature. Both ∗Research Associate, AIAA Member †Associate Professor, AIAA Member ‡Research Associate, AIAA Member