..., this study identifies a threshold for the combination of slip parameters: below this threshold, drag torque increases, but it sharply decreases above it. Originality/value This study showcases that the rotational speed of the Tesla disc for zero torque initially increases with small slips but decreases...

.... It is determined physically, the wall expansion mechanism requires more torque with less drag. With the plausible approximations as used in Garrett (2002), the boundary layer fluid flow due to the motion of the sphere is governed by the following unsteady Navier–Stokes equations in spherical coordinates...

...Maged A.I. El‐Shaarawia; Ali A. Al‐Ugla Purpose The paper seeks to focus on obtaining the transient torque required to rotate the inner cylinder in open ended vertical concentric annuli for a fluid of Pr = 0.7 in the laminar natural convection flow regime over a wide range...