On the orientational dependence of drag experienced by spheroids

On the orientational dependence of drag experienced by spheroids

Pacha Sanjeevi, S.K. (TU Delft Intensified Reaction and Separation Systems)
Padding, J.T. (TU Delft Intensified Reaction and Separation Systems; Eindhoven University of Technology)

2017

The flow around different prolate (needle-like) and oblate (disc-like) spheroids is studied using a multi-relaxation-time lattice Boltzmann method. We compute the mean drag coefficient CD,ϕ at different incident angles ϕ for a wide range of Reynolds numbers ( Re ). We show that the sine-squared drag law CD,ϕ=CD,ϕ=0∘+(CD,ϕ=90∘−CD,ϕ=0∘)sin2ϕ holds up to large Reynolds numbers, Re=2000 . Further, we explore the physical origin behind the sine-squared law, and reveal that, surprisingly, this does not occur due to linearity of flow fields. Instead, it occurs due to an interesting pattern of pressure distribution contributing to the drag at higher Re for different incident angles. The present results demonstrate that it is possible to perform just two simulations at ϕ=0∘ and ϕ=90∘ for a given Re and obtain particle-shape-specific CD at arbitrary incident angles. However, the model has limited applicability to flatter oblate spheroids, which do not exhibit the sine-squared interpolation, even for Re=100 , due to stronger wake-induced drag. Regarding lift coefficients, we find that the equivalent theoretical equation can provide a reasonable approximation, even at high Re , for prolate spheroids.

multiphase and particle-laden flows
particle/fluid flow

http://resolver.tudelft.nl/uuid:ae34984f-0c44-4958-945b-9b4b42bd909f

https://doi.org/10.1017/jfm.2017.239

2017-11-02

0022-1120

Journal of Fluid Mechanics, 820

Accepted Author Manuscript

Institutional Repository

journal article

© 2017 S.K. Pacha Sanjeevi, J.T. Padding