TY - JOUR

T1 - Effect of particle density in turbulent channel flows with resolved oblate spheroids

AU - Eshghinejadfard, Amir

AU - Hosseini, Seyed Ali

AU - Thévenin, Dominique

N1 - Funding Information:
The authors acknowledge the financial support of the EU-programme ERDF (European Regional Development Fund) grant no. ZS/2016/4/78155 within the research Center of Dynamic Systems (CDS).
Publisher Copyright:
© 2019 Elsevier Ltd

PY - 2019/4/30

Y1 - 2019/4/30

N2 - The present paper studies the effect of particle density in a turbulent channel flow laden with resolved oblate spheroids at a frictional Reynolds number of Re τ =180. Direct numerical simulations are performed by using the lattice Boltzmann method (LBM) for solving the flow field. Particle-fluid interactions are modeled by the immersed boundary method (IBM). Simulations are done for dense regimes of heavy and neutrally-buoyant particles with a volume fraction of 5%. The particle-fluid density ratios are 8.0 and 1.0 for heavy and neutrally-buoyant particles, respectively. Results show that particle inertia can significantly modify the fluid and particle statistics. Heavy particles cause a higher reduction of the fluid streamwise velocity with respect to the single-phase flow. Turbulence is attenuated by both particle types but the reduction is stronger with heavy particles than that with neutrally-buoyant ones. Moreover, increasing the density of particles is found to create smaller but more energetic vortices. Quadrant analysis shows that the contribution of ejection and sweep events in the Reynolds shear stress reduce on increasing the particle density. The local volume fractions of the two particle types are also seen to be different. While the volume fraction of neutrally-buoyant particles reach a constant value at a certain distance from the walls, the concentration of heavy oblate spheroids increases gradually all the way up to channel center. Both particle types show preferential orientation near the walls, where the symmetry axis is normal to the wall. However, this preferential orientation is less pronounced when increasing the particle inertia. Finally, the translational velocity fluctuations of heavy particles are found to be higher in the streamwise direction, but lower in the wall-normal direction.

AB - The present paper studies the effect of particle density in a turbulent channel flow laden with resolved oblate spheroids at a frictional Reynolds number of Re τ =180. Direct numerical simulations are performed by using the lattice Boltzmann method (LBM) for solving the flow field. Particle-fluid interactions are modeled by the immersed boundary method (IBM). Simulations are done for dense regimes of heavy and neutrally-buoyant particles with a volume fraction of 5%. The particle-fluid density ratios are 8.0 and 1.0 for heavy and neutrally-buoyant particles, respectively. Results show that particle inertia can significantly modify the fluid and particle statistics. Heavy particles cause a higher reduction of the fluid streamwise velocity with respect to the single-phase flow. Turbulence is attenuated by both particle types but the reduction is stronger with heavy particles than that with neutrally-buoyant ones. Moreover, increasing the density of particles is found to create smaller but more energetic vortices. Quadrant analysis shows that the contribution of ejection and sweep events in the Reynolds shear stress reduce on increasing the particle density. The local volume fractions of the two particle types are also seen to be different. While the volume fraction of neutrally-buoyant particles reach a constant value at a certain distance from the walls, the concentration of heavy oblate spheroids increases gradually all the way up to channel center. Both particle types show preferential orientation near the walls, where the symmetry axis is normal to the wall. However, this preferential orientation is less pronounced when increasing the particle inertia. Finally, the translational velocity fluctuations of heavy particles are found to be higher in the streamwise direction, but lower in the wall-normal direction.

KW - Heavy particle

KW - Lattice Boltzmann method

KW - Oblate spheroid

KW - Turbulent flow

UR - http://www.scopus.com/inward/record.url?scp=85063743283&partnerID=8YFLogxK

U2 - 10.1016/j.compfluid.2019.01.027

DO - 10.1016/j.compfluid.2019.01.027

M3 - Article

AN - SCOPUS:85063743283

SN - 0045-7930

VL - 184

SP - 29

EP - 39

JO - Computers and Fluids

JF - Computers and Fluids

ER -