The poloidal asymmetries of parallel flows in edge plasmas are investigated by the 3D fluid turbulence code TOKAM3X. A diverted COMPASS-like magnetic equilibrium is used for the simulations. The measurements and simulations of parallel Mach numbers are compared, and exhibit good qualitative agreement. Small-scale turbulent transport is observed to dominate near the low field side midplane, even though it co-exists with significant large-scale cross-field fluxes. Despite the turbulent nature of the plasma in the divertor region, simulations show the low effectiveness of turbulence for the cross-field transport towards the private flux region. Nevertheless, a complex pattern of fluxes associated with the average field components are found to cross the separatrix in the divertor region. Large-scale and small-scale turbulent transport, along with the drift, drive the asymmetries in parallel flows. A semi-analytical model based on mass and parallel momentum balances allows the poloidal drift effects on the asymmetry pattern to be evaluated. As in the experiments, a reversed B T simulation provides a way of self-consistently separating the effects of turbulent transport and large-scale flows, which must be reversed for a reversed field. The large-scale contribution is found to be responsible for typically 50% of the effect on the Mach number, evaluated at the top of the machine. The presented picture shows the complex interplay between drifts and turbulence, underlining the necessity of a global approach to edge plasma modelling, including a self-consistent description of the turbulence.

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International audienceIn order to improve cross-field transport description, drifts and currents have been implemented in SOLEDGE2D–EIRENE. The derivation of an equation for the electric potential is recalled. The resolution of current equation is tested in a simple slab case. WEST divertor simulations in forward-B and reverse-B fields are also discussed. A significant increase of ExB shear is observed in the forward-B configuration that could explain a favorable L-H transition in this case

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