A numerical method based upon the immersed boundary technique for thefluid-solid coupling and on a soft-sphere approach for solid-solid contact isused to perform direct numerical simulation of the flow-induced motion of athick bed of spherical particles in a horizontal plane channel. The collisionmodel features a normal force component with a spring and a damper, as well asa damping tangential component, limited by a Coulomb friction law. The standardtest case of a single particle colliding perpendicularly with a horizontal wallin a viscous fluid is simulated over a broad range of Stokes numbers, yieldingvalues of the effective restitution coefficient in close agreement withexperimental data. The case of bedload particle transport by laminar channelflow is simulated for 24 different parameter values covering a broad range ofthe Shields number. Comparison of the present results with reference data fromthe experiment of Aussillous et al. (J. Fluid Mech. 2013) yields excellentagreement. It is confirmed that the particle flow rate varies with the thirdpower of the Shields number once the known threshold value is exceeded. Thepresent data suggests that the thickness of the mobile particle layer(normalized with the height of the clear fluid region) increases with thesquare of the normalized fluid flow rate.
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