Computation of a three-dimensional uniform, steady Newtonian flow past oblate spheroidal particles is undertaken. The main objective of the present study is to compute the hydrodynamic forces on oblate spheroidal particles as a function of the particle orientation, for different particle aspect ratios and a large range of particle Reynolds number. The results of the simulations are used to provide a new complete set of correlations for drag, lift, and torque coefficients. These correlations are derived for an aspect ratio ranging from 0.2 to 1, for particle Reynolds number up to 100, and for all orientations. In addition, it is found that the Stokesian evolution of the drag and lift coefficients as a function of the incidence remains still valid at moderate particle Reynolds number; that is, drag coefficient evolves as sine squared and lift coefficient evolves as (sin ϕ cos ϕ).

Direct numerical simulations (DNSs) have been performed to examine the inertia, shape, and gravity field effects on the dynamics of ellipsoidal particles within a vertical turbulent channel flow. To investigate the effects induced by the particle inertia and shape, computations have been conducted for three aspect ratios and two response times. The influence of gravity has been examined through a comparison with DNS data provided in earlier studies without gravity. The originality of this study is that the prediction of the hydrodynamic force and pitching torque acting on the non-spherical particles has been carried out with recent expressions valid outside the Stokes flow regime. With the data extracted from the DNS, a statistical analysis of the particle spatial distribution, orientation, and translational and angular velocities is carried out. Results show that the presence of a significant mean relative velocity between the dispersed and continuous phases greatly modifies the dynamics of non-spherical particles. Without gravity, the dynamics of ellipsoids is close to that of spheres, whereas it becomes strongly dependent on the particle shape with gravity.

Computation of a dilute suspension of prolate spheroidal particles in a turbulent channel flow is undertaken to study the influence of inertia and shape on acceleration statistics. A pseudo-spectral direct numerical simulation is coupled with Lagrangian tracking under the one-way coupling assumption. Simulations are carried out at friction Reynolds number , for three aspect ratios , 3 and 10, and two Stokes numbers St=5 and 30. Results indicate that, as a consequence of the filtering effect of inertia, particle acceleration RMS decreases with increasing inertia. In addition, the normalised streamwise acceleration PDFs depart from that of the conditional fluid and their tails become narrower as inertia is increased. Furthermore, acceleration statistics show that particle elongation has a significant effect on the mean drag and on the particle selective sampling. Moreover, the classification of elongated particle behaviour in turbulent channel flow based on a global Stokes number is questioned. The zero-crossing acceleration autocorrelation timescales presented points out the need for a local dimensionless number estimation adapted to the case of prolate spheroids.

In this work, a computational fluid dynamics of a linear shear flow past an oblate spheroid resting on a surface was conducted. The present study aims to compute the hydrodynamic forces experienced by oblate spheroids in contact with a smooth surface. Using the computational results, we derive correlations for the hydrodynamic drag, lift, and drift coefficients. These correlations are provided for an aspect ratio ranging from 0.2 to 1, for particle Reynolds numbers up to 7. In addition, it is found that the Stokesian evolution of the drag coefficient as a function of the orientation remains valid in the considered configuration; that is, the drag coefficient evolves as a so-called “square-sine” profile. Surprisingly, it was found that the lift induced by shear was also found to evolve as “square-sine” with respect to the spheroid orientation. Furthermore, we found that the drift coefficient evolves as a so-called cosine-sine profile with respect to the spheroid orientation.