Is the critical Reynolds number universal?

This paper is devoted to checking whether the critical Reynolds number is universal in identical conditions for the flow of different fluids. The laminar-turbulent transition in a circular pipe flow has been tested experimentally. The flows of inert gases (He, Ne, Ar, Kr, Xe), molecular gases (N-2, CO, CO2, SF6), and two similar liquids (H2O, D2O) have been tested. A considerable, up to 40%, difference in critical Reynolds numbers was observed. The possible reasons for nonuniversality of the critical Reynolds number are discussed. (C) 2002 MAIK Nauka/Interperiodica.