Narrow Results

Liquid metal first wall is attractive in fusion reactor designs because of its high heat removal and self-refreshment capabilities. In liquid wall study, method of forming stable liquid flows on the front surface of blanket has to be found. In order to do this, free surface magneto-hydrodynamic (MHD) effects and flow velocity distributions of liquid metal under gravity have been studied. In our study, liquid metal flows down along ducts half-opened to face the plasma. Net electromagnetic force forms from induced eddy current interacting with the confinement magnetic field (12T) in the liquid metal flow. For liquid metal lithium (about 4cm thick), distributions of velocity along the flow direction have been obtained by combined calculations of free surface flow and electromagnetic analysis. The results show that MHD baffle might be used to get stable in front of the blanket.

The traditional weakly compressible SPH (WCSPH) method has been reported to suffer from large density variations, resulting in non-physical pressure fluctuations. In this article, a truly incompressible SPH (ISPH) method is developed and extended to free surface flows of shear-thinning fluids, in which the viscosity is modeled by the Cross model. The ISPH method employs a pressure Poisson equation to satisfy the incompressibility constraints, and the Navier-Stokes equations are solved in a Lagrangian form using a two-step fractional method. The method is firstly verified by solving the impact of a Newtonian droplet with a horizontal rigid plate in comparison with the available literature data. Then, ISPH is extended to simulate the phenomena of a Newtonian and a Cross droplet impact and spreading over an inclined rigid plate. In particular, the different flow features between Newtonian and Cross droplets after the impact are discussed. All numerical results show that ISPH method can not only extend to free surface flows of shear-thinning fluids, but also reduce the pressure noise in comparison with WCSPH.

In this paper a new approach is developed to simulate the extrudate swell of viscoelastic fluid. Lattice Boltzmann model is used to solve the complex Navier-Stokes equations and constitutive equations simultaneously at each time iteration. The type of cell is re-initialized by calculating the mass fluxes between neighboring cells after each iteration. The boundary conditions are treated with the non-equilibrium extrapolation method. Finally, by tracking the moving interface, the shape of the extrudate swell is acquired.