Turbulence modification by inertial particles and its influence on the spectral energy budget in planar Couette flow

Abstract

Two-way coupled, particle-laden simulations are performed in turbulent Couette flow with the purpose of investigating the spectral extent of the particle influence on the turbulent energy cascade in wall-bounded flows. Direct numerical simulation of the carrier phase is performed in conjunction with the Lagrangian point-particle approximation for particles of three distinct inertia ranges: StK = [O(1),O(10),O(100)]. Simulations are also performed at three increasing Reynolds numbers (Reτ ≈ [125,325,900]) to determine the longevity of these effects as the scale separation between large and small motions is increased. A spectral decomposition of the turbulent kinetic energy (TKE) budget shows that two simultaneous effects of particles are occurring: first, the mere presence of particles causes a reduction of TKE production across nearly the entire wavenumber range, where the particle Stokes number only determines the magnitude of this reduction; second, the direct energy exchange term between the carrier and dispersed phases is relatively small in magnitude compared to changes in production; however, its location in wavenumber space is highly dependent on Stokes number and is influenced heavily by preferential concentration. The combined effect of these distinct processes is important to consider when developing large eddy simulation (or any other) two-way coupled particle-laden turbulence parameterizations.