Abstract: The Roe flux-difference splitting scheme is widely used to simulate subsonic and transonic flow fields due to its characteristics of small dissipation, high resolution, etc. However, an entropy correction method should be proposed when the space is discrete. And the entropy correction will increase dissipation and affect the prediction accuracy of drags. Based on the characteristics of entropy correction for the Roe scheme of the unstructured hybrid grid, a new entropy correction method is presented by improving the original Harten-Yee entropy correction method. To validate the new method, a numerical simulation of the DLR-F4 wing-body configuration is performed. The numerical results are analyzed and compared with that of the original Harten-Yee entropy correction method and no-entropy method. The results indicate that the same residual convergence and more accurate results can be obtained with the new method, and the results show a good agreement with experiment results and the results obtained with no-entropy method. It is found that the new method not only retains the advantages such as robustness, but also minimizes the effect on the prediction accuracy of drags. That verifies the effectiveness of the new method. The DLR-F6 wing-body model of the 3th AIAA Drag Prediction Workshop is studied elaborately using the new method. The influences of grid convergence and Reynolds numbers are studied. The results demonstrate that the new method is much more suitable for viscous calculation of the unstructured hybrid grid, and the precision is similar to the corresponding CFD software. The drag prediction accuracy of the new method is further verified.

Key words: hybrid grid, drag prediction, Roe scheme, entropy correction, DLR-F4 wing-body configuration, DLR-F6 wing-body configuration