FLOW STRUCTURE OF THERMAL COUNTERFLOW JET IN HE-II

The flow structure of a thermal counterflow jet is investigated by dir ect measurement of the normal fluid velocity with a laser Doppler velo cimeter (LDV). The temporal and spatial variation of the normal fluid velocity is measured to investigate the detailed properties of a He II thermal counterflow jet. The velocity profile and the variation of th e centre-line velocity with the axial distance are also obtained to de termine the flow structure in the downstream region. It is found that the thermal counterflow jet in the far-field behaves like a fully deve loped turbulent jet in an ordinary fluid. However, it seems that the m ode of development differs from that of an ordinary fluid jet.