Prolate spheroidal particles’ behavior in a vertical wall-bounded turbulent flow

Abstract

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.

Forces and torques on a prolate spheroid: low-Reynolds-number and attack angle effects

“…[20] and Ouchene et al [32]. The latter formula has been corrected for some typos pointed out by Arcen et al [3]. The attack angle dependence of CD is also shown in Figure 9, but for higher Reynolds numbers.…”

“…In an earlier paper by Jiang et al [23] we showed computed results for drag, lift and torques for a 6:1 prolate spheroid at 45° attack at Re = 50 and compared with the Hölzer and Sommerfeld [20] and Zastawny et al [50] correlations. Such force-and torque-correlations have recently been used in simulations of turbulent channel flow by van Wachem et al [46], Tavakol et al [44] and Arcen et al [3].…”

“…This is obviously associated with the separated flow behind the spheroid seen in Figure 6(d), which inevitably increased the pressure drag. [32] corrected for some typos pointed out by Arcen et al [3]. Entries for θ = 0° and 90° are not included.…”

Correlations for inclined prolates based on highly resolved simulations

“…This definition is consistent with the most recent efforts to model the forces and torques via empirical correlation functions by Zastawny et al (2012), Ouchene et al (2016) and Sanjeevi, Kuipers & Padding (2018). Lately, the functions by Ouchene et al (2016) have been reformulated by Arcen et al (2017). In Ouchene et al (2016), drag and lift force correlations are derived for and using a commercial solver to generate the data.…”

Response Behavior of Nonspherical Particles in Homogeneous Isotropic Turbulent Flows

“…Again the hydrodynamic forces and torques were computed with Stokes regime expressions. Beyond the Stokes regime, van Wachem et al [28] and Ouchene et al [29] studied a turbulent channel flow laden with ellipsoidal particles using LES and DNS, respectively, employing the flow coefficients developed by themselves in previous works.…”