A gas bubble in a liquid, such as a simple air bubble in water can resonate when it is excited with an acoustic wave at the bubbles natural resonant frequency. So we have resonance effects in fluid-gas systems.
What about the case of fluid-solid system. Say we have some circular rods made of a solid material and we place them in a liquid. Is it possible to have resonance in this case?
Imagine that you have some circular rods.
They will have some natural frequencies of oscillation.
If these roods are dirty you might put them into an ultrasonic cleaning bath and the rods will have dirt removed from them by the water transmitting ultrasonic vibrations to the metal rings and causing them to vibrate.
If you could change the frequency of the sound waves you could imagine that there will be frequencies at which the metal rings exhibit maximum amplitude vibrations - resonance.
