STUDY OF FULLY-DEVELOPED, LAMINAR, AXIAL-FLOW AND TAYLOR VORTEX FLOW BY MEANS OF SHEAR-STRESS MEASUREMENTS

The results of a shear stress investigation for combined axial and rotational flow, under conditions of both laminar flow and laminar flow plus Taylor vortices, are presented. These results show that two distinct regimes of shear stress dependency exist. In the primary regime, the shear stress is constant and depends only on the imposed axial flow, the flow being either laminar (Poiseuille and Couette flows) or laminar with vortices, but with the effect of the vortices being negligible. In the secondary regime, the shear stress is shown to depend only on Ta**0**. **7**3**5, irrespective of the imposed axial flow. At low axial flow rates, a tertiary regime was observed, but no satisfactory explanation can be found for this phenomenon. The demarcation between the primary and secondary flow regimes differs markedly from those of other investigators. In the present study, the critical conditions are determined by the point at which vortices begin to have an effect on measurements taken at the outer annular wall rather than the conditions under which vortices are initially formed. Evidence is presented for the vortices being formed within a confined layer near to the inner cylinder and thereafter growing with increasing rotational speed until the outer annular wall is approached, resulting in the much higher critical conditions found in the present study.