Wall shear stress in the helical annular flow with rotating inner cylinder

An experimental and numerical investigation has been performed in order to study the appearance of hydrodynamic instabilities at low bulk axial Reynolds number in the gap between two coaxial cylinders with a diameter ratio of 0.52, 0.8 and 0.9, whose outer cylinder is stationary and the inner one is rotating. Skin friction coefficient and wall shear stress have been measured for fully developed laminar flows of water when the inner cylinder rotates at the speed of 0600 rpm. The axial component of velocity is directly affected by the radial/tangential velocity field and rotation of the inner cylinder is found to have a strong influence on the axial velocity distribution, ultimately leading to two maximum in the case of high eccentred inner cylinder at high rotational speeds.