Use a harmonic analysis to calculate the complex pressure distribution for high operating frequencies. The complex pressure distribution can be used to extract a damping coefficient and a stiffness coefficient. The phase shift between the pressure and the velocity is caused by compression of the fluid. The real pressure component contributes to the damping of the system. The imaginary pressure component contributes to the stiffening of the system.
FRe is the real component of the pressure force. FIm is the imaginary component of the pressure force. Omega (ω) is the frequency (rad/sec). The damping and stiffness coefficients are frequency-dependent. Figure 3.4: Damping and Squeeze Stiffness Coefficients vs. Frequency illustrates the frequency dependency for a typical microsystem application.
The DMPEXT command is used to extract frequency-dependent damping parameters for use with the MDAMP, DMPRAT, ALPHAD, and BETAD command inputs.