Determination of instantaneous flow resistance coefficients of oblate ellipsoids at intermediate Reynolds numbers

• Published in: Physics of fluids (1994) Vol. 37; no. 6
• Main Authors: Laín, S., Castang, C., Chéron, V.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.06.2025
• Subjects: Aspect ratio; Correlation; Direct numerical simulation; Drag; Ellipsoids; Flow characteristics; Flow coefficients; Flow resistance; Fluid dynamics; High Reynolds number; Lift; Particle interactions; Particle shape; Reynolds number; Torque; Uniform flow; Unsteady flow
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/5.0270024

This study investigates the hydrodynamic behavior of oblate ellipsoidal particles immersed in a uniform flow, focusing on their flow resistance coefficients, including drag, lift, and pitching torque. Using advanced particle-resolved direct numerical simulations (PR-DNS), the research explores fluid-particle interactions across a range of aspect ratios ( AR = 1.25, 2.5, 5, 10), orientation angles ( 0°≤α≤90°), and Reynolds numbers ( Rep ≤ 200), relevant to industrial and environmental processes. The simulations reveal significant unsteady flow characteristics past oblate particles with AR larger than 5, and values of Rep larger than 100, resulting in oscillatory behaviors in the hydrodynamic force coefficients, which vary with the aspect ratio of the particle. The contributions of pressure and friction to the force coefficients are analyzed individually, providing insights into how aspect ratio and Reynolds number influence flow behavior. At high Reynolds number, the fluctuations are not negligible and the root mean square (rms) values of flow coefficient fluctuations are also provided, distinguishing between periodic and aperiodic regimes. The results of the accurate unsteady PR-DNS are used to derive novel correlations to predict the drag, lift, and torque coefficients of oblate ellipsoidal particles subject to locally uniform flows. A good agreement is observed between the PR-DNS results and the correlations, with median errors of 1.40%, 2.57%, and 3.09%, for the correlations predicting the drag, lift, and torque coefficients, respectively. These correlations can be used to improve Eulerian–Lagrangian frameworks and provide valuable insights into the role of particle shape and orientation in hydrodynamic interactions within complex flow environments.