This discussion led me to read the EPO Patent Application more carefully. I never really bothered with this one becasue it was "old" and no actual patent was ever issued that I can tell.
In Meyer's EP0 103656 Patent Application, Meyer explains what he means by resonance and resonant cavity. Meyer says:
"The spacing between the plates comprises a resonant cavity to a particular frequency. The direct current voltage is pulsed at a
repetition rate that matches the frequency of the resonant cavity."
In this same document Meyer goes on to say:
"It has been found that the distance between the plates of the exciters will have, or can be adjusted to have, a wavelength, or
partial wavelength, or multiple wavelength related to the motion of the water molecule in traveling from one plate to the other."
And in refering to the spherical plate device:
"...the distance from the outer surface of the central element to the inner surface of the outer spherical element will be at some
wavelength to the molecular motion of travel. When the wavelength is matched with a physical force equal in frequency to that
wavelength, the inner area becomes a resonant cavity and the water molecule will forcefully be driven repeatedly."
Meyer uses the term "physical force equal in frequency". I take this to mean the motion/inertia of the water molecule and not the pulsed DC, as that would be an electrical force. Meyer goes on to say that coaxial tubes work in the same manner as the spherical design.
So when we take Meyer literally, the resonant cavity is not the tube itself but the space between the 2 tubes. Therefore, the "wavelength" and the related resonant frequency of the cavity , is a function of the distance betweeen the tubes and not the resonant frequency of the tube itself (as if it were an organ pipe). It is not likely that the wavelength of the acoustic resonant frequency of the tubes will be the same as the wavelength of the distance between the tubes.
Does anyone see where I am going with this ?
Goey