'Pumping' action of a rotating fluid flow

Experimental results are reported on the behavior of a viscous elastic fluid in a spherical resonator with two orifices which is excited by monochromatic deformation waves of low amplitude and frequency. The rotating fluid was found to have a 'pumping' effect, i.e., the fluid particles rotated synchronously in the resonator so as to induce an axisymmetric incoming flow in one orifice and an axisymmetric outgoing flow in the other. The pumping was caused by the deformation waves, which excited the resonator at its natural frequency, and a mechanism is proposed and verified experimentally. The distinctive feature of pumping rotational flows is that the fluid (gas or liquid) in the resonator rotates about an axis normal to the plane containing the axes passing through the orifices at which the acoustic wave energy is radiated (reflected) and absorbed in the resonator; gas is sucked into the absorbing orifice and expelled from the reflecting orifice.