Euler–Lagrange modeling of sediment–turbulence interactions in horizontal channel flow

Euler–Lagrange (EL) modeling of sediment-laden, highly turbulent channel flows remains challenging particularly in the near-wall region, because sediment particles are relatively large compared with the local flow scales. The accuracy of EL simulations can deteriorate in two-way and four-way coupled simulations, especially in the presence of large particles relative to the local resolved scales. The issue arises in the inter-phase coupling where the particle force is added to the adjacent fluid-phase momentum equations that introduces disturbance in the local flow field. Using the disturbed field to compute particle forces in subsequent time steps can lead to inaccuracies that become more pronounced as the particle size increases relative to the local flow scales. This occurs because most closure models are derived based on the undisturbed background flow, which is no longer available in the two-way (and four-way) coupled simulations. In this study, a newly developed corrected EL approach coupled with large eddy simulations is employed to model sediment–turbulence interactions in a horizontal channel flow with a Reynolds number of Reτ=583.3 defined based on the bed friction velocity. Sediment particles near the bed are fully resolved in the wall-normal direction (dp+=5.77) but under-resolved in the streamwise and spanwise directions. The recently developed correction scheme by Pakseresht et al. [“A correction scheme for wall-bounded two-way coupled point-particle simulations,” J. Comput. Phys. 420, 109711 (2020)] is employed to adjust the EL approach and recover the undisturbed flow field required for accurate force estimation of large particles. The corrected EL approach successfully captures several key experimental observations of sediment-laden, wall-bounded turbulence, including (i) an increase in the bed friction velocity, (ii) damping of the mean fluid velocity in the outer layer and enhancement in the inner layer, and (iii) increases in turbulence intensities and Reynolds shear stress quadrants near the bed. The promising results and findings of this study can lead to further improvements in the EL predictions of wall-bounded, particle-laden, highly-turbulent flows.