In 2018, I have been granted an ANR JCJC (young researcher) for 4 years to develop new sediment transport experiments, acquire new high-resolution data and develop accurate subgrid models for Eulerian-Eulerian two-phase flow models for sediment transport applications. Please find below a short summary of the project.

  • Julien CHAUCHAT (PI - associate prof., GINP, LEGI)
  • David HURTHER (senior researcher, CNRS, LEGI)
  • Guillaume BALARAC (associate prof., GINP, LEGI)
  • Cyrille BONAMY (research engineer, CNRS, LEGI)
  • Tian-Jian HSU (Prof., University of Delaware, USA)
  • Helder GUTA (PhD student, 2019-, LEGI)
  • Antoine MATHIEU (PhD student, 2018-, LEGI)

The project SHEET-FLOW develops a two-phase flow approach that potentially incorporates most of the physical processes at stake. It relies on a close synergy between modelling and advanced acoustic instrumentation resolving velocities and concentration at the turbulent scales. This program will be applied to the well-controlled open-channel flows in the 10-m tilting flume facility available at LEGI (Grenoble, France). A wide range of flow conditions and sediment properties will be tested involving lightweight PMMA particles (1 and 3 mm size) and medium and coarse sands. The flow forcing will cover the sheet flow regime or intense bed-load transport corresponding to Shields number in 0.5 to 2. For these conditions, particles inertia is expected to influence sediment fluxes and turbulence damping mechanisms. Another important feature is the role of intermittent sediment bursts on the hydrodynamic roughness. All these processes will be investigated during the project.

Manip1 Manip2 Manip3

The ultimate goal of the SHEET-FLOW project is to develop accurate Sub-Grid Scale (SGS) models for turbulence resolving two-phase flow simulations or Large Eddy Simulations (LES) of sediment transport in the sheet flow regime. These SGS models encompass fluid-particle forces and fluid and particle phases stress. Different modeling choices will be tested among which the Germano’s decomposition, the gradient diffusion model (istotropic and anisotropic) and the dynamical structure model. A priori analysis of high-reosolution LES simulations will be used to infer the functional dependencies of the sub-grid models on local filtered variables, such as velocity, concentration and their spatial gradients, as well as the grid size. The two-phase LES results will be used to investigate the fine-scale processes leading to turbulence modulation mechanisms, turbulent dispersion of particles and the interplay of intermittent turbulence and inter-granular interaction on the resulting transport dynamics under sheet flow conditions. The methodology will consist in investigating the turbulent kinetic energy budget and the relative contributions of the different stresses to the overall.

Artistic view of turbulence resolving two-phase flow simulation of suspended-load (sedFOAM)

The LES results will be used to derive turbulence-averaged parameterizations for two-phase flow models. This last objective is critical to accurately upscale fine-scale turbulence-particle interaction processes in larger scale problems such as dunes evolution during river floods, wave driven sediment transport over sandbars or turbidity currents at the continental margins.