Underexpanded Micro-nozzle Flow Simulation with Coupled Thermal-Fluid Modeling

Simulation of micro-thrusters intended for space propulsion relies on accurate modeling of those physical processes that occur highly coupled in the micron-sized scale. In fact, micronozzles exhibit significant differences when compared to their large-scale counterparts, so their modeling requires accounting for specific aspects to achieve success in the prediction. The goal of the present investigation is to simulate the steady and transient operation of a micro-thruster in underexpansion for cold and hot inert gas under a multiphysics, continuum-based Navier-Stokes approach with slip-flow conditions. The modeling incorporates three major effects: gas rarefaction in the slip regime, viscous dissipation and solid-gas heat transfer. Non-equilibrium effects have been addressed with the implementation of a 2^nd -order slip-model for velocity and temperature on the walls. The results summarize the attained micro-thruster performance and wafer thermal response. Their dependence on the thermal-fluid coupling is analyzed.