Investigation of bulk turbulence and nonlinear wave phenomena in liquid helium

Subharmonic Generation/Bifurcation In Liquid Helium--Measurements of the thresholds for the generation of first-sound sub-harmonics show a classical liquid response above the superfluid transition (T = 2.17 K) and bifurcation following the Feigenbaum universal convergence ratio below the superfluid transition. Ion-trapping techniques reveal that the threshold for the generation of the first subharmonic response corresponds to the threshold for acoustic generation of quantum vortex line. Acoustic Streaming In Liquid Helium--Quantitative measurements of acoustic streaming shows a classical response above T= 2.17 K. Below the superfluid transition we have shown that only the normal fluid component streams and that the temperature and frequency dependences are in quantative agreement with the Khalatnikov two-fluid hydrodynamic equations if the coefficient of second viscosity is properly taken into account. Heat Transfer between Copper and Liquid Helium--A conventional Kapitza resistance experiment with an acoustic streaming field directed transverse to the surface normal shows (1) no enhanced heat transfer below the superfluid transition and (2) above the superfluid transition the thermal conductance increases linearly with acoustic velocity amplitude reaching a value of 2.5 times the no sound level for a sound velocity amplitude of 0.8 centimeters/second.