Modeling drag force in ellipsoidal particle suspensions with preferential orientation.

High aspect ratio ellipsoidal particle suspensions exhibit preferential orientation under the action of external forces and in the presence of walls. The preferential orientation of the particles has a large effect on the drag force experienced by the suspension. In this paper particle resolved simulations are conducted on ellipsoidal particles of aspect ratio 10 and 2.5 in the Reynolds number range 10 ≤ Re ≤ 200 and solid fractions 0.10 ≤ φ ≤ 0.30. An orientational order parameter −2.0 ≤ S ≤ 1 is used to define the preferential orientation of the suspension. It is shown that in spite of up to 400% variation in mean drag force with S , a simple linear relationship between S = −2 and 1 can describe the variation of drag force. This is a significant finding which establishes that only two data points at S = −2 and 1 are needed to define mean drag at any preferential orientation exhibited by the suspension. It is also shown that the inclination dependent mean drag is quite independent of S at low Reynolds number and solid fraction but shows increasing dependence at higher values. Unlabelled Image • Particle-resolved simulations are performed for prolate ellipsoid suspensions. • Orientational order parameter (S) is used to quantify the orientation preference. • Mean drag shows linear dependence on orientational parameter S. • Inclination dependent drag force is independent of S at low solid fraction (φ). • At larger φ , drag increases with S at identical inclination angles. [ABSTRACT FROM AUTHOR]