hi, I am modelling an ultrasonic standing wave field acting on suspended particles in a continuous medium. I am just curious. Do the acoustic radiation forces act on the continuous medium too? For example in an oil-in-water emulsion, do the acoustic radiation forces act on the water (continuous phase)? Or is it only on the oil droplets (suspended particles)?
Ideally yes, but maneuvering the desired particle will depend on the difference in acoustic impedance of the two mediums and the directivity (beam-width) of your ultrasonic beam.
yes, on both, actually, acoustic radiation are pressure waves forcing both the medium and suspended particles. Can not exist acoustic radiation without the medium. However, small particles whose size is comparable to the radiation wavelength, absorbe and react easily to the acoustic waves.
Yes, the Ultrasound field act on the two medium, because is a wave that propagates in the mixed medium, and the acoustic force (Primary and secondary bjerknes) in the case of a standing wave will segregates the two phases (if the power is lower than the cavitation threshold) or will mix them even in a stronger way (if the power is higher than the cavitation threshold)
However if you have only water (or only oil) the acoustic field will generate bubbles (if there are oxygen with in), and you could probably have luminescence effect.
Acoustic radiation pressure acts on interfaces. In the bulk, there is a similar phenomenon called acoustic streaming which creates steady currents.
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