New results in cryogenic helium flows at ultra-high Reynolds and Rayleigh numbers

Liquid helium I, II and cryogenic helium gas are used to generate and study highly turbulent flows under controlled laboratory conditions. These three working fluids have remarkable versatility, allowing extremely large value s and dynamic ranges of the Reynolds (Re) and Rayleigh (Ra) numbers to be r eached. In particular, cryogenic helium gas has been used to study turbulen t thermal convection in a range 10(6) less than or equal to Ra 10(17), by f ar the largest ever attained in a controlled experiment on turbulence. The upper limit exceeds previous studies by nearly three orders of magnitude.