Nonlinear, Parametric Generation of Sound by Resonant Mode Conversion.
Abstract
When nonlinear terms are included in the two fluid hydrodynamic descriptions of superfluid helium4, first sound (pressuredensity waves) and second sound (temperatureentropy waves) are coupled. The interaction of two second sound waves to produce a propagating first sound wave is shown to occur at a specific angle which makes the point of intersection of the second sound waves travel at the speed of first sound. The growth of the mode converted first sound wave is calculated with and without attenuation of the primary (second sound) waves from 1.2 K to 2.15 K and from saturated vapor pressure to twenty atmospheres. An experiment to observe this mode conversion process in a waveguide to rectangular crosssection is described.
 Publication:

Ph.D. Thesis
 Pub Date:
 1977
 Bibcode:
 1977PhDT........47G
 Keywords:

 Physics: Acoustics;
 Helium Isotopes;
 Nonlinear Systems;
 Parametric Amplifiers;
 Propagation Modes;
 Resonance;
 Sound Generators;
 Superfluidity;
 Wave Interaction;
 Coupled Modes;
 Entropy;
 Hydrodynamics;
 Sound Pressure;
 Waveguides;
 Acoustics