Effects of large computational time steps on the computed turbulence were investigated using a fully implicit method. In turbulent channel flow computations the largest computational time step in wall units which led to accurate prediction of turbulence statistics was determined. Turbulence fluctuations could not be sustained if the computational time step was near or larger than the Kolmogorov time scale.

Effects of the computational time step on numerical solutions for turbulent flow

Evaporation model for interfacial flows based on a continuum-field representation of the source terms

Blanket/first wall challenges and required R&D on the pathway to DEMO

http://www.fusion.ucla.edu/abdou/abdou%20publications/2007/JCP-v227-NiCurrentPart1.pdf

A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part I: On a rectangular collocated grid system

http://www.fusion.ucla.edu/abdou/abdou%20publications/2007/JCP-v227-NiCurrentPart2.pdf

A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part II: On an arbitrary collocated mesh

Progress on the modeling of liquid metal, free surface, MHD flows for fusion liquid walls

Direct simulation of falling droplet in a closed channel

http://www.fusion.ucla.edu/abdou/abdou%20publications/2008/FED-v83-MorleyMHDsimulations(2008).pdf

MHD simulations of liquid metal flow through a toroidally oriented manifold

A general formula for the second-order projection method for solution of unsteady incompressible Navier-Stokes equations is presented. It includes the four- and three-step projection methods. Also, RKCN (Runge-Kutta/Crank-Nicholson) three-step and four-step projection methods are presented, in which the three-stage Runge-Kutta and semi-implicit Crank-Nicholson techniques are employed to update the convective and diffusion terms, respectively. The RKCN projection method is further simplified. The pressure Poisson equation (PPE) is solved only at the final substage for the simplified RKCN projection method, which greatly reduces the computation time. The high-order boundary conditions for the intermediate velocities have also been given for the four-step RKCN projection method and its simplified version. A 2-D vortex flow, a 2-D oscillating cavity flow, and a 3-D lid-driven cavity flow are simulated to validate the analysis. The projection method is also used to do the direct numerical simulation (DNS) of a...

http://www.fusion.ucla.edu/neil/Publications/ProjectionMethodsfortheCalculation.pdf

Projection methods for the calculation of incompressible unsteady flows

A general formula for the second-order projection method combined with the level set method is developed to simulate unsteady, incompressible multifluid flow with phase change. A subcell conception is introduced in a modified mass transfer model to accurately calculate the mass transfer across the interface. The third-order essentially nonoscillatory (ENO) scheme and second-order semi-implicit Crank-Nicholson scheme is employed to update the convective and diffusion terms, respectively. The projection method has second-order temporal accuracy for variable-density unsteady incompressible flows as well. The level set approach is employed to implicitly capture the interface for multiphase flows. A continuum surface force (CSF) tension model is used in the present cases. Phase change and dynamics associated with single bubble and multibubbles in two and three dimensions during nucleate boiling are studied numerically via the present modeling. The numerical results show that this method can handle com...

http://www.fusion.ucla.edu/abdou/abdou%20publications/2005/NHT-Bv48p425-444.pdf

Ming-Jiu Ni

Papers

Progress on the modeling of liquid metal, free surface, MHD flows for fusion liquid walls

Direct simulation of falling droplet in a closed channel

MHD simulations of liquid metal flow through a toroidally oriented manifold

Projection methods for the calculation of incompressible unsteady flows

Numerical Modeling for Multiphase Incompressible Flow with Phase Change