Study of the Stagnation-Point Boundary Layer in Hypersonic Magnetohydrodynamic Flows

To investigate the effect of a magnetic field on the stagnation-point boundary layer in hypersonic flows, this study developed a magnetohydrodynamic boundary-layer model that incorporates real gas effects. Variations in the boundary layer, including stagnation-point heat flux, heat transfer function, and skin friction function, were examined to elucidate the mechanisms associated with different boundary-layer-edge conditions. Parameters at the boundary-layer edge were obtained using the quasi-one-dimensional stagnation streamline method. The results indicate that the nonequilibrium state at the boundary-layer edge has minimal impact on the inner boundary layer. In contrast, the magnetic strength reduces convective heat transfer primarily by decreasing the velocity gradient at the boundary-layer edge. The enhancement of the heat transfer function is mainly driven by the “acceleration effect” on the flow within the boundary layer, resulting from decreased velocity gradients and increased Lorentz force. This interaction ultimately leads to a saturation effect in the reduction of heat transfer. Additionally, the increase in the skin friction function is primarily due to velocity overshoot within the boundary layer induced by the magnetic field. The Lorentz force induced by the magnetic field expands the inviscid shock layer while simultaneously reducing the boundary-layer thickness. Overall, the stagnation-point boundary-layer model developed in this study not only facilitates rapid assessment of stagnation parameters, but also deepens our understanding of the magnetic field’s role within the stagnation-point boundary layer.