Numerical Modeling of Axisymmetric and Three-Dimensional Flows in Microelectromechanical Systems Nozzles

A numerical study of three-dimensional effects on the performance of a micronozzle fabricated from  at silicon wafers is performed by use of both continuum and kinetic approaches. The nozzle operates in a low-Reynoldsnumber regime, and viscous effects dominate the gas expansion. Thrust losses occur because the shear on the wall is greater in a  at nozzle conŽ guration than in an axisymmetric conical nozzle. Therefore, the prediction of the micronozzle performance based on axisymmetric or two-dimensional modeling can lead to signiŽ cant design errors. Comparisonof simulationwith recent data shows good agreement in terms of thrust predictions for cold-gas thrusters at Reynolds numbers of approximately 2 £ £ 102.