PULSED NONLINEAR SOUND IN SUPERFLUID HE-4 AND HE-4-HE-3 MIXTURES

Sound modes in He-4 and He-4-He-3 mixtures which arise out of the two- fluid equations are made up zip a vector convective flow and scalar te mperature changes. A method for modeling nonlinear pulses of sound wit h geometric approximations to the vector and scalar components has rec ently been applied towards understanding nonlinear second sound near t he lambda point.(6) The same method may be used, in general, for model ing linear and nonlinear sounds in Helium II. We demonstrate with a mo del for nonlinear second sound pulses in He-3-He-4 mixtures and compar e the results to experimental observations.