0000000000358720
AUTHOR
R. P. Wehrum
On the existence of higher waves in a layer of superfluid helium
The two implicit equations that contain the dispersion laws of waves propagating in a He II layer of variable thickness are formally investigated for solutions that go beyond those associated with the layer modifications of first and second sound: A series of symmetric and antisymmetric layer modes are found to exist by calculating the distribution of roots of the dispersion equations in the complex wave number plane as a function of layer thickness and angular frequency. All these modes turn out to be strongly attenuated and can be regarded as layer modifications of the viscous wave. Phase velocities, attenuation coefficients, and velocity profiles of some of them are calculated numericall…
Dispersion relations of wave modes in helium II layers
Dispersion relations of (sound-like) wave modes, which can exist in a helium II layer of arbitrary width, are calculated numerically. The basis of our considerations is the complete system of the linearized Landau-Khalamikov equations, in which only the dissipative processes involved with η and ζ2 are taken into account. Apart from the linearization, no approximation or averaging is performed. The thermal expansion of helium II is taken into account. Symmetry properties of the velocities of flow, usually required, are dropped here. A hint is given as to how all the Khalatnikov coefficients may be measured by sound absorption experiments.