UNS3D Near-Field Predictions for the Third AIAA Sonic Boom Prediction Workshop

Abstract

This paper presents the results of turbulent flow simulations prepared for the Third AIAA Sonic Boom Prediction Workshop. Solutions were prepared for two geometries that exhibited shock–plume interaction features: the NASA biconvex shock–plume interaction wind-tunnel model, and the NASA C608 low-boom concept aircraft. The unstructured, finite volume Navier–Stokes solver UNS3D was used to predict the turbulent near-field flow with Menter’s shear stress transport turbulence model. Four solver setups with different combinations of the flux function, gradient reconstruction, and slope limiter were applied to each geometry. UNS3D predictions were compared against a grid-specific ensemble dataset created using workshop participant submissions and experimental data when available. Predictions of the biconvex geometry were found to be in good agreement with both the experimental and ensemble datasets. The weighted least-squares with QR decomposition (LSQR) gradient reconstruction approach was only successful for the biconvex geometry, with no converged cases being achieved on C608 grids. The Dervieux limiter, used only to aid simulations on the C608 using weighted LSQR, was observed to be too dissipative to be of practical use. Near-field predictions of the C608 geometry using Green–Gauss gradient reconstruction and a modified Venkatakrishnan limiter were found to correlate well with the ensemble data. The perceived level of the resulting sonic boom carpet was 1.5 dB quieter along the first 20 deg of the carpet than the ensemble mean, and it peaked at an azimuth angle of 30 deg with a value of 76.1 dB. A study of the undertrack near-field pressure signature revealed the components of the predicted signatures responsible for the variances observed in the sonic boom carpet.