Turbulent Helical Flow in an Annulus

Turbulent flow of an incompressible fluid in the annular space between concentric rotating cylinders with an axial pressure gradient is investigated experimentally and theoretically. The concept of a tensor eddy viscosity is used to develop the theory which predicts mean velocity distributions and resistance characteristics of fully developed turbulent flow in an annulus with either rough or smooth boundaries. Resistance characteristics and transition phenomena are observed in an annulus with the inner cylinder rotating. For a given axial flow, the axial resistance increases with increasing speed of rotation, in agreement with theoretical predictions. The transition from purely turbulent flow to turbulent flow with vortices, as inferred from changes in axial pressure gradient, is found to occur at a constant value of the ratio of average axial velocity to tangential velocity. For a given angular velocity, the tangential resistance is found to be reduced by the introduction of axial flow.