AN EXPERIMENTAL-STUDY OF A SUPERFLUID TURBULENT THERMAL COUNTERFLOW JET USING A LASER-DOPPLER VELOCIMETER

Superfluid turbulent feature of a thermal counterflow jet is investiga ted using a laser Doppler velocimeter. The velocity distribution and t urbulent nature in the downstream region of a jet are found similar to those of ordinary fluids, but the evolution to the fully developed tu rbulent jet occurs much faster than ordinary fluid jets. The decay rat e of the 2nd sound Helmholtz oscillation indicates the flow state for small heat input is in a weak superfluid turbulent state different fro m a fully developed superfluid turbulent state. The transition from th e weak to the fully developed states is found to be characterized by t he increase in the turbulent fluctuation of the velocity.