The turbulent flow between concentric cylinders both rotating in the same or opposite directions is investigated theoretically. A finite difference scheme is developed to solve the boundary layer equations covering the flow. A two-equation model of turbulence was employed in this study. Modifications have been made to the model to take into account the effect of rotating on of the cylinders and the existing of the wall. The effect of changing the radius ratio, axial Reynolds number and angular velocity ratio on the hydraulic friction head loss of air is studied . Distributions for axial mean velocity, tangential mean velocity, turbulence intensity and shear stress in both the entrance region and fully developed region are predicted, also. Comparisons of the present numerical results with other investigators results show good agreement.
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