Three dimensionality of pulsed second-sound waves in He II

Three dimensionality of three-dimensional (3D) pulsed second-sound waves in He II emitted from a finite size heater is experimentally investigated and theoretically studied based on the two-fluid model in this study. The detailed propagation of the 3D pulsed second-sound wave is presented and reasonable agreement between the experimental and theoretical results is obtained. Heater size has a big influence on the profile of the 3D second-sound wave. The counterflow between the superfluid and normal fluid components becomes inverse in the rarefaction of the 3D second-sound wave. The amplitude of rarefaction decreases due to the interaction between second-sound wave and quantized vortices, which explains the experimental results about the second-sound wave near ${T}_{\ensuremath{\lambda}}$ [L. C. Krysac, Phys. Rev. Lett. 73, 2480 (1994)]. The accumulation of dense quantized vortices in the vicinity of heater surface leads to the formation of a thermal boundary layer, and further increase of heating duration results in the occurrence of boiling phenomena.