The laminar-turbulent transition for flow in pipes, concentric annuli, and parallel plates

Recently Ryan and Johnson proposed a stability parameter for pipe flow. For Newtonian fluids they showed that this parameter Z is proportional to the critical Reynolds number (D anti nu rho/..mu..) and is given by the relation Z = 2 ..sqrt..1/27 N/sub Rec/. They also demonstrated the utility of Z as a stability parameter for the isothermal pipe flow of power-law non-Newtonian fluids. In the present paper a generalized stability parameter will be proposed which is independent of the geometry of the flow system, is proportional to the Reynolds number for Newtonian flow, and contains Ryan and Johnson's results for pipe flows in general as a special case.