APM Liquid Loading

In modeling the interaction of a liquid with plate modes, the high frequency of operation necessitates the consideration of viscoelastic response by the liquid. For the simple liquids examined, good agreement was obtained by modeling the liquid as a Maxwellian fluid with a single relaxation time r. When the Maxwellian fluid is driven in oscillatory flow with cot 1, it responds as a Newtonian fluid characterized by the shear viscosity, rj. For wt 1, the oscillation rate approaches the rate of molecular motion in the liquid and energy ceases to be dissipated in 

Viscous coupling of plate modes to an adjacent fluid results in both attenuation of the plate mode and a change in propagation velocity. These can be estimated from a perturbation analysis and are given by [54] 

The effect of liquid entrainment on APM propagation has several inqilica-tions. First, the sensitivity of the device to liquid viscosity enables the device to 

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