Numerical simulation of heat transfer and pressure distributions in micronozzles with surface discontinuities on the divergent contour

• We model a rarefied flow in array-arranged convergent–divergent micronozzles.
• We investigate the influence of the curvature and discontinuities on the divergent surface contour.
• Computational results indicate a small dependence of the surface aerothermodynamic loads on the divergent curvature.
• Presence of sharp corners along the divergent contour has a strong effect in the surface coefficients

This work describes two-dimensional numerical simulations of rarefied gas flows in convergent–divergent micronozzles. Array-arranged micronozzles with rectangular cross-section and convex–concave divergent shape are considered. The primary goal of this paper is to assess the sensitivity of the pressure, skin friction and heat transfer coefficients as well as the impact on the specific impulse due to the presence of surface discontinuities on the divergent contour of the micronozzles. The knowledge of thermal and mechanical loads present on the micronozzle surfaces is essential to predict operational conditions of a propulsive system. Because of the rarefied nature observed in micronozzle flows and the ability to deal with complex geometries, the Direct Simulation Monte Carlo method is employed to simulate the flow structure. For the conditions investigated, the computational results indicate a small dependence of the surface aerothermodynamic loads on the divergent curvature. On the other hand, these loads were strongly affected by the existence of singularities on the divergent contour, e.g., sharp corners. In spite of these findings, the specific impulse computed along the exit section was essentially the same for all investigated cases.