Thermal and flow effects of corner rounding in rarefied hypersonic step flows

This paper examines the effects of corner rounding on the rarefied hypersonic flow over forward steps. The impact of upper corner and upper-lower corner rounding of step on the vortex structure, flow, and wall properties are investigated at different Knudsen and Mach numbers. Considering that previous studies mainly focused on sharp-edged steps, the novelty of present study lies in investigating the corner rounding influences on flow and surface parameters, especially the vortex dynamics and thermal loads. Results indicate that rounding the step corner(s) reduces the vortex size, the flow-field hot spot temperature, and the maximum pressure and heat transfer coefficients on the wall. Upper-lower corners rounding can eliminate the vortex at sufficiently high rounding radii. The vortex vanishes at lower rounding radii as the Knudsen number increases. Higher Knudsen numbers lead to increased surface pressure and heat transfer coefficients and smaller vortices at a constant rounding radius. The results indicate that the maximum wall heat transfer coefficient is more sensitive to step rounding under less rarefied conditions. Conversely, the hot spot temperature within the domain is more sensitive to step corner rounding at higher Knudsen numbers. Higher Mach numbers lead to enhanced heat transfer and pressure coefficients. The peak surface heat transfer and pressure coefficients exhibit more sensitivity to rounding radius at higher Mach numbers.