Numerical Investigation of Dual-Mode Operation in a Rectangular Scramjet Flowpath

Abstract

Three-dimensional turbulent simulations with combustion modeling are employed to understand fundamental phenomena encountered in the Hypersonic International Flight Research Experimentation Flight 2 scramjet flowpath. Experimental data from the ground-test campaign as well as a grid resolution study are used to validate the results of the simulations. These confirmed results are then leveraged to explain the physics of dual- and scramjet-mode operation in a steady sense, including detailed examinations of shock structure, boundary-layer separation, and combustion chemistry. Simulations of the flight and ground tests are compared in order to characterize the effects of the inlet on the boundary-layer development and internal shock structures. Overall, agreement with ground-test data is excellent, and the simulations show highly complex three-dimensional structures in the flowpath. Boundary-layer separation induced shock–boundary-layer interactions dominate dual-mode operation, whereas at higher Mach numbers a flameholding effect of the barrel shock from fuel injection is striking. The effects of the inlet are found to be of great importance to accurately model flight tests; however, the same macroscale effects as observed in the ground-test simulations are dominant. These steady simulations set the stage for future transient simulations focusing on mode-transition and unstart.