Study and modification of cross-flow induced transition model based on local variables

The transition prediction model proposed by Langtry and Menter needs to be modified for predicting cross-flow induced transition. Local variable Helicity is found to be capable of indicating cross-flow information in the boundary layer, so it can be used to construct cross-flow transition prediction which is compatible with complex configuration and modern computational fluid dynamics (CFD) parallelized computation. The cross-flow transition prediction model based on Helicity parameter is realized and has the ability to capture the influence of different Reynolds numbers for infinite swept wing NLF(2)-0415 with sweep angle of 45°. However, the difference between the realized model result and experimental data for 6:1 prolate spheroid is large. In this paper, cross velocity factor is considered to modify the realized model aimed at improving the shortcoming of realized model. The solver of cross velocity is simplified and approximated for local calculation, which makes the modified cross-flow model retain the superiority of totally using only local variables. Finally, NLF(2)-0415 wing, 6:1 prolate spheroid and DLR-F5 wing are simulated by the modified model. The comparison between the simulation and experiment data indicates that the modified cross-flow transition prediction model can capture cross-flow induced transition phenomenon.