Assessment of Near-Field Sonic Boom Simulation Tools

Abstract

A recent study for the Supersonics Project, within the National Aeronautics and Space Administration, has been conducted to assess current in-house capabilities for the prediction of near-field sonic boom. Such capabilities are required to simulate the highly nonlinear flow near an aircraft, wherein a sonic-boom signature is generated. There are many available computational fluid dynamics codes that could be used to provide the near-field flow for a sonic boom calculation. However, such codes have typically been developed for applications involving aerodynamic configuration, for which an efficiently generated computational mesh is usually not optimum for a sonic boom prediction. Preliminary guidelines are suggested to characterize a state-of-the-art sonic boom prediction methodology. The available simulation tools that are best suited to incorporate into that methodology are identified; preliminary test cases are presented in support of the selection. During this phase of process definition and tool selection, parallel research was conducted in an attempt to establish criteria that link the properties of a computational mesh to the accuracy of a sonic boom prediction. Such properties include sufficient grid density near shocks and within the zone of influence, which are achieved by adaptation and mesh refinement strategies. Prediction accuracy is validated by comparison with wind tunnel data. Nomenclature

Analysis of the Effects of Streamwise Lift Distribution on Sonic Boom Signature

“…The cause of its existence in CFD may be due to inaccurate sting geometry or lack of viscous effects. Similar result for the tail is shown in other validation attempts done by Casper 18 and Wintzer…”

Near field Sonic Boom calculation of Benchmark Cases

“…As the initial trails, the RANS model with Baldwin-Lomax model was used and the near field sonic boom was significantly over-predicted due to the boundary layer thickness. The calculation is then switched to inviscid calculation as the methods used by other groups [42,40,43,44]. The rear part of the cone with constant radius cylinder is extended to the exit boundary for the simplicity of boundary condition treatment.…”

Lobe Balancing Design Method to Create Frozen Sonic Booms Using Aircraft Components

“…The surface geometry from VSP was input into the Cart3D CFD code to obtain pressure profiles. Cart3D was selected because it has been widely used for sonic boom research and has shown good agreement compared with experimental results [56,57]. For this study, Cart3D was used on a workstation at the U.S. Air Force Academy Modeling and Simulation Center.…”

“…Cart3D's adjoint mesh refinement routine was used to increase resolution in the vicinity of the sonic boom. Based on previous sonic boom studies [56,57], the objective function…”