Numerical study of three-dimensional flow and aerodynamic characteristics of a cylindrical cavity in rarefied hypersonic flows

Abstract

Cylindrical cavity configuration frequently appears on the surface of an aerospace vehicle while flow physics of rarefied hypersonic flows over it are not clear yet. This work presents a comprehensive numerical study to reveal flow structures inside the cavity and aerodynamic surface quantities, including the pressure on and heat flux to the surfaces of three-dimensional cylindrical cavities using the DSMC method. The results showed that the traditional cavity flow types based on the classical categorization are not suitable for characterizing rarefied hypersonic flows over cylindrical cavities due to more diverse flow patterns induced by the curved cylindrical sidewall, especially for the cylindrical cavity with a shallow depth. Both the pressure on and heat flux to the striped area near the top lip of downstream curved sidewall are always the strongest due to the violent airflow collision there, which is a depth range of about 0.4 y/H away from the top lip, but those for the cavity floor are usually quite weak because the gas over it moves slowly. With the increase of cavity depth, the weaker pressure on and heat flux to the cavity floor appear because the rising curved sidewall makes it more difficult for freestream to permeate into the cavity, whereas the maximum pressure on and peak heat flux to the downstream curved sidewall seem to be unchanged. The severe rarefaction effect at 90 km make the flow pattern and temperature distribution inside the cavity different from those for 50, 60, and 70 km. As the freestream Mach number is increased from 13.4 to 33.5, the streamline patterns and velocity contours around and inside the cavity only change slightly, consequently leading to similar numerical trends of both the pressure on and heat flow to the cavity surfaces.