Numerical study on three-dimensional effects in a supersonic strut-jet turbulent combustion flow

The supersonic combustion flow experiment conducted by the German Aerospace Center (DLR) employs a strut-based jet as a flame stabilization device, yielding comprehensive measurements including pressure, velocity, temperature and root mean square of turbulent fluctuating velocity. This dataset serves as a critical validation case for flamelet model evaluation. Previous RANS studies predominantly adopted two-dimensional (2D) simulations to simplify mesh generation. However, the DLR combustor configuration with 15 circular fuel injection holes inherently suggests three-dimensional (3D) flow characteristics. This study systematically compares 2D and 3D RANS approaches while varying the number of modeled fuel injectors (1-3 holes) to investigate geometrical dimensionality effects. Results reveal that under non-reacting conditions, congruence between the 3D computational solutions of single- and triple-injector configurations is observed, rendering fuel injector quantity irrelevant in 3D simulations. For reacting cases, weak inter-injector interactions cause minor discrepancies between the 3D computational results of single- and three-injector configurations. In both non-reacting and reacting flows, fuel injected from circular injectors initially exhibits three-dimensional effects. Turbulent mixing causes the spanwise gradients of flow parameters to diminish. Beyond 15 mm downstream of the injector exits, both non-reacting and reacting flows transition to quasi-2D states. Consequently, the flow distributions within the combustor predicted by 2D RANS have satisfactory agreement with 3D RANS results. Thus, 2D RANS can provide grid simplification advantages while maintaining reasonable fidelity.