Contribution to the 7th AIAA CFD Drag Prediction Workshop Using TAS-code and FaSTAR

Abstract

This work summarizes the contribution of the Japan Aerospace Exploration Agency (JAXA) to the 7th AIAA CFD Drag Prediction Workshop (DPW7). This workshop aims at assessing the capabilities of state-of-the-art computational fluid dynamics (CFD) solvers at off-design conditions on industry relevant geometries, such as the NASA Common Research Model (CRM) wing-body configuration, for which experimental data are available from different wind tunnel facilities. Using the committee-provided 6-member family grids, Reynolds-averaged Navier-Stokes (RANS) calculations have been performed with two of JAXA’s in-house solvers, namely TAS-code and FaSTAR, for the grid convergence (case 1), angle of attack sweep (case 2) and Reynolds number sweep (case 3) studies. For the simulations at target lift-coefficient of 0.58 in case 1, the flow is fully attached on the aircraft and good grid convergence is obtained. The grid sensitivity at high angles of attack, for which large separations occur, remains to be determined. The angle of attack sweep study in case 2 shows that the quadratic constitutive relation (QCR) needs to be applied to the one-equation Spalart-Allmaras model with rotation correction (SA-R) to avoid overpredicting the side-of-body separation. The aerodynamic coefficients differ with the experimental results and need to be arbitrarily shifted to at least match the measurements at low angles of attack. This shift is intended to group all numerical and experimental uncertainties and its necessity is currently under discussion within the workshop. In case 3, when Reynolds number and dynamic pressure are changed, the correct drag trends are captured. When TAS-code and FaSTAR used the same turbulence model, remarkable agreement was achieved, and these results are consistent with those of the other DPW7 participants. The differences with the reference experiments and the difficulties in understanding their origin suggest that a more detailed characterization of the experimental setup is required in order to promote CFD progress in adequately capturing the flow physics during off-design phases of the flight envelope.