Effect of particle orientation on the drag force in random arrays of prolate ellipsoids in low‐Reynolds‐number flows

This work provides a recipe for creating drag, lift and torque closures for static assemblies of axisymmetric, non-spherical particles. Apart from Reynolds number Re and solids volume fraction ǫ s , we propose four additional parameters to characterize the flow through non-spherical particle assemblies. Two parameters consider the mutual orientations of particles (the orientation tensor eigenvalues S 1 and S 2 ) and two angles represent the flow direction (polar and azimuthal angles α and β). Interestingly, we observe that the hydrodynamic forces on the particles are independent of the mutual particle orientations. Rather, the most important parameter representing the particle configuration itself is the incident angle φ of the individual particles with respect to the incoming flow. Moreover, we observe that our earlier finding of sine-squared scaling of drag for isolated particles (Sanjeevi & Padding 2017) holds on average even for a multiparticle system in both the viscous and inertial regimes. Similarly, we observe that the average lift for a multiparticle system follows sine-cosine scaling, as is observed for isolated particles. Such findings are very helpful since the pressure drop of a packed bed or porous media can be computed just with the knowledge of orientation distribution of particles and their drag at φ = 0 • and φ = 90 • for a given Re and ǫ s . With the identified dependent parameters, we propose drag, lift and torque closures for multiparticle systems.

S = (〈〉, {bold-italicpp}^{T}) .

…”

Section: Simulation Setupmentioning

confidence: 99%

Hydrodynamic forces on monodisperse assemblies of axisymmetric elongated particles: Orientation and voidage effects

Sanjeevi

Padding

2020

“…Since nonspherical particles are popular in practical applications, some researchers have focused on formulating the drag relation for isolated nonspherical particles. For a comprehensive review on this topic, the reader can refer to Li et al 7 …”

Section: Introductionmentioning

confidence: 99%

“…In CFD‐DEM simulations, 8‐10 the most used approach to calculate the drag force on nonspherical particles at arbitrary solid volume fractions and particle orientations is to combine the drag correlation for isolated nonspherical particles proposed by Holzer and Sommerfeld 11 and the correction factor proposed by Di Felice 12 . However, through comparing with the results from PR‐DNSs, researchers 7,13‐15 reported that this approach might not be sufficiently accurate since it under‐predicted the drag force on nonspherical particles at various occasions.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, for multi‐particle systems with nonspherical particles, the majority of studies are focused on investigating the drag force on elongated particles, such as prolate ellipsoids 7 and fibers 16 . Limited studies pay attention to oblate ellipsoids even if they are one of the most commonly particles in industrial applications.…”

Section: Introductionmentioning

confidence: 99%

“…However, they restricted their simulations in close‐packed dense flows. Most recently, Li et al 7 systematically performed PR‐DNSs of flow past arrays of ellipsoids under different conditions. They found that, other than the solid volume fraction, the particle orientation and the aspect ratio AR also have marked effects on the drag force experienced by ellipsoids.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of particle orientation on the drag force in random arrays of oblate ellipsoids in low‐Reynolds‐number flows

Jiang

Huang

et al. 2020

Self Cite

Through particle‐resolved direct numerical simulations of flows past random arrays of oblate ellipsoids at low Reynolds numbers, this work demonstrates how the drag force on oblate ellipsoids depends on the Hermans orientation factor S, the mean crosswise sphericity φ⊥, the aspect ratio AR, and the solid volume fraction c. Wide ranges of S, AR, and c are considered and they are in the intervals (−0.5, 1), (0.2, 0.8), and (0.1, 0.4), respectively. This study extends the work on prolate ellipsoids by Li et al (AIChE Journal, 2019, 65, e16621). Based on the simulation results, two models are respectively developed using S and φ⊥as the independent orientation factor. The model based on S could give accurate prediction of the drag force and the lateral force exerted on arrays of particles. The model based on φ⊥ is able to use one generalized drag correlation for both oblate and prolate ellipsoids.

Effect of anisotropic microstructures on fluid–particle drag in low‐Reynolds‐number monodisperse gas–solid suspensions

Chen

et al. 2020

Local structural anisotropy prevails in gas–solid suspensions. It causes strong fluctuations in the drag on individual particles. In this work, the anisotropy of microstructures is quantified by a second‐order structure tensor, which is determined with a directionally dependent mean free path length. Direct numerical simulations of low‐Reynolds‐number flows past anisotropic and isotropic BCC, FCC, and random arrays of monodisperse spheres in sufficiently large domains are performed. The results show that, at the same solid volume fraction, the differences between the mean drag in principal directions of anisotropic arrays and that in isotropic arrays correlate well with functions of eigenvalues of the structure tensor for the anisotropic arrays. Anisotropic drag models for different arrays are proposed. Assessment of the model for random arrays shows that it well captures fluctuations in the mean drag at microscales of several sphere diameters, where the traditional model fails to give satisfactory predictions.