Inertial torque on a small spheroid in a stationary uniform flow
Peer reviewed, Journal article
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Original versionPhysical Review Fluids. 2021, 6 . 10.1103/PhysRevFluids.6.024302
How anisotropic particles rotate and orient in a flow depends on the hydrodynamic torque they experience. Here we compute the torque acting on a small spheroid in a uniform flow by numerically solving the Navier-Stokes equations. Particle shape is varied from oblate (aspect ratio λ = 1 / 6 ) to prolate ( λ = 6 ) , and we consider low and moderate particle Reynolds numbers ( Re ≤ 50 ) . We demonstrate that the angular dependence of the torque, predicted theoretically for small particle Reynolds numbers, remains qualitatively correct for Reynolds numbers up to Re ∼ 10 . The amplitude of the torque, however, is smaller than the theoretical prediction, the more so as Re increases. For Re larger than 10, the flow past oblate spheroids acquires a more complicated structure, resulting in systematic deviations from the theoretical predictions. Overall, our numerical results provide a justification of recent theories for the orientation statistics of ice crystals settling in a turbulent flow.