3D simulations with k-epsilon realizable turbulence model

Simulations with finer mesh

Hypothesis and Goals

The preliminary 3D simulations using k-epsilon realizable (RKE) turbulence model failed to converge to a satisfactory level. Based on the results and discussion of previous models , a finer mesh in z-direction should the first attempt to resolve the convergence issue.

Methods and Procedures

The mesh of 2D models is swept in the z-direction with a width of 0.1m (lengthxheightxwidth(x*y*z) = 0.2*1*0.1), and a mesh interval size of 0.002m (#intervals=50), which is in the same order of magnitude as that of x and y directions.

Preliminary Observations and Discussion (on-going simulation)

Since the finer mesh contains 1,500,000 cells, which is 50 times as many as that of the 2D mesh and 70 times as big as the 2D mesh in terms of the file size, the iteration takes about 30 seconds per step. After about 3000 iterations for 30 hours, the residual plots showed a promising tend to fall below a satisfactory level. (The simulations is still running at this moment)

The plot of the residual of

Energy dissipation contour of 2D model, k-epsilon realizable 1.5b

Energy dissipation contour of 3D model with periodic boundary condition, k-epsilon realizable

Since there is no variation in the z-direction in 3D model, the results from 2D is completely duplicated, which agrees with the underlying simplification of 2D simulation.

An important lesson

In FLUENT, the material property, in this case water liquid should be defined in the boundary conditions as well as in the material list. The default material in FLUENT is always air, which need to be checked and modified correctly before every simulation.

Report summary is a very good way to keep track of all the parameter settings. And more effective and efficient way of data management is necessary for carry out simulation experiments efficiently.