Articles | Volume 5, issue 2
Research article
17 May 2017
Research article |  | 17 May 2017

Physical theory for near-bed turbulent particle suspension capacity

Joris T. Eggenhuisen, Matthieu J. B. Cartigny, and Jan de Leeuw

Abstract. The inability to capture the physics of solid-particle suspension in turbulent fluids in simple formulas is holding back the application of multiphase fluid dynamics techniques to many practical problems in nature and society involving particle suspension. We present a force balance approach to particle suspension in the region near no-slip frictional boundaries of turbulent flows. The force balance parameter Γ contains gravity and buoyancy acting on the sediment and vertical turbulent fluid forces; it includes universal turbulent flow scales and material properties of the fluid and particles only. Comparison to measurements shows that Γ = 1 gives the upper limit of observed suspended particle concentrations in a broad range of flume experiments and field settings. The condition of Γ > 1 coincides with the complete suppression of coherent turbulent structures near the boundary in direct numerical simulations of sediment-laden turbulent flow. Γ thus captures the maximum amount of sediment that can be contained in suspension at the base of turbulent flow, and it can be regarded as a suspension capacity parameter. It can be applied as a simple concentration boundary condition in modelling studies of the dispersion of particulates in environmental and man-made flows.

Short summary
Suspension of particles in turbulent flows is one of the most widely occurring physical phenomena in nature, yet no theory predicts the sediment transport capacity of the wind, avalanches, pyroclastic flows, rivers, and estuarine or marine currents. We derive such a theory from universal turbulence characteristics and fluid and particle properties alone. It compares favourably with measurements and previous empiric formulations, making it the first process-based theory for particle suspension.