Simulation of gas damping in microstructures with nontrivial geometries

Methods to calculate the fluid depending forces in movable micromechanical structures will be shown in this paper. In most cases fluid flow within narrow air gaps can be simply described by the Reynolds gas film equation. Analytical solutions are known for simple plate shapes. New ways to describe the damping and squeeze film effect for nontrivial plate shapes using analogy relations are discussed. Reynolds equation fails in the case of large air gaps between plates or if free outstream conditions are not valid. In these cases the general Navier-Stokes-Equation must be used. FE-tools with fluidmechanical capabilities are able to solve this partial differential equation and allow a damping analysis. Phase shift between plates velocity and reaction forces can be interpreted as additional inertial or squeeze forces. Results of simulation and experimental analysis are verified on a gyroscope and a micromirror array