Wall Effects on the Rheology of Dilute Suspensions of Ellipsoidal Particles

This study investigates the effect of walls on the rheology of dilute suspensions of neutrally buoyant ellipsoidal particles in shear flow at low Reynolds numbers. Due to

their geometry, ellipsoids follow Jeffery orbits under shear, characterized by the orbit constant C. We examine two limiting cases - log-rolling and tumbling. To isolate wall effects, particle interactions are minimized by maintaining a dilute regime and fixed volume fraction while varying wall separation (Ly). Rheological quantities such as intrinsic viscosity, stresslet, Reynolds stresses, and normal stress differences are analyzed. Reducing Ly increases intrinsic viscosity; for example, at Re = 1, it is 19.26% higher at Ly = 1.2 than at Ly = 3.0. In tumbling, confinement also enhances stresslet asymmetry and magnitude and amplifies normal stress differences. For log-rolling, the first normal stress difference increases while the second decreases with decreasing Ly. These findings serve as a foundation for future studies on suspensions of “hairy” structures, modeled as porous shells with solid cores.