Particle motions in sheared suspensions: IX. Spin and deformation of threadlike particles

Abstract The axial spin of slightly curved but rigid cylindrical particles rotating in a velocity gradient have been shown to be in good accord with Jeffery's theoretical equation for ellipsoids of revolution provided that the equivalent ellipsoidal axis ratio is substituted for the true axis ratio in the equation. A theory of deformation of cylindrical particles rotating in a velocity gradient is presented. Equations are developed to calculate the critical value of (gradient × viscosity) at which the shear-induced axial compression causes the particle to buckle. Experiments conducted with Dacron, Nylon, and rayon filaments cut to various axis ratios and dispersed in various liquid media showed reasonably good agreement with the theory. Some observations of the increase of particle deformation beyond the critical gradient for bending are presented.