A numerical and experimental investigation of rolling and sliding motion of rotating spheres inside a cylinder

Rotating spheres in cylindrical channels roll or slide along the channel depending on physical and geometric conditions. For a thorough investigation of phenomenon, finite-element modelling is utilized to obtain resistance coefficients for motion sphere channel, with an emphasis near-wall motion. Extracted are compared data literature exploring conditions rolling versus sliding channel. Sliding occurs due pressure build-up nip region between wall rotating small confinement ratios, whereas when shearing forces dominant larger ratios. According numerical results, flow reversal takes place reduces shear as well. Rolling demonstrated experiments by using magnetic spherical particles, which rotated means external field inside filled viscous fluids. Faster axial velocities observed narrow while than wider same rotation rate sphere. Experiment observations evaluated from coefficients, showing that distance wall, dominated roughness, plays important role velocity