Forcing homogeneous turbulence in direct numerical simulation of particulate flow with interface resolution and gravity
Abstract
We consider the case of finitesize spherical particles which are settling under gravity in a homogeneous turbulent background flow. Turbulence is forced with the aid of the random forcing method of Eswaran and Pope ["An examination of forcing in direct numerical simulations of turbulence," Comput. Fluids 16(3), 257278 (1988)], while the solid particles are represented with an immersedboundary method. The forcing scheme is used to generate isotropic turbulence in vertically elongated boxes in order to warrant better decorrelation of the Lagrangian signals in the direction of gravity. Since only a limited number of Fourier modes are forced, it is possible to evaluate the forcing field directly in physical space, thereby avoiding fullsize transforms. The budget of boxaveraged kinetic energy is derived from the forced momentum equations. Mediumsized simulations for dilute suspensions at low Taylorscale Reynolds number Re_{λ} = 65, small density ratio ρ_{p}/ρ_{f} = 1.5, and for two Galileo numbers Ga = 0 and 120 are carried out over long time intervals in order to exclude the possibility of slow divergence. It is shown that the results at zero gravity are fully consistent with previous experimental measurements and available numerical reference data. Specific features of the finitegravity case are discussed with respect to a reduction of the average settling velocity, the acceleration statistics, and the Lagrangian autocorrelations.
 Publication:

Physics of Fluids
 Pub Date:
 December 2015
 DOI:
 10.1063/1.4936274
 arXiv:
 arXiv:1511.02638
 Bibcode:
 2015PhFl...27l3301C
 Keywords:

 Physics  Fluid Dynamics
 EPrint:
 accepted for publication in Phys. Fluids