Particle-resolved direct numerical simulation of particle-laden turbulence modulation with high Stokes number monodisperse spheres

Graphic processing units (GPU)-accelerated direct numerical simulations of particle-fluid systems based on lattice Boltzmann method combined with discrete element method are successfully performed. This method is validated to be accurate and efficient in the four-way coupling simulation of particle-fluid systems. Particle-laden homogeneous isotropic turbulence under particle size d(p) = 30.1 eta (the Kolmogorov length scale), a wide range of solid volume fraction phi V = 2 % - 20 % and particle Stokes number St = 503.87 - 50 387 are systematically studied. The additional energy dissipation rate epsilon(addi) induced by particles is quantitatively calculated. One criterion for turbulence enhancement or attenuation based on energy balance is proposed and successfully used in different particle-laden turbulence. The relative magnitude of two-way coupling rate psi and particle-induced dissipation epsilon(addi) is the direct factor determining the modulation effect on turbulence. Turbulence laden with high Stokes number particles is enhanced. Turbulence laden with high volume fraction particles transited rapidly from enhancement to attenuation, which is attributed to the more rapid decay of psi relative to epsilon(addi) in the freely decaying turbulence.