Generally, the agreement between simulation and experimental
results improve as the mesh size used in the simulations decreases. It
is also frequently found that, as the fluid velocities increase, turbulence
is needed in the fluid flow simulations to obtain agreement with experimental
observations. The need for fine mesh and the incorporation of turbulence
in the fluid flow simulations for the phenomena taking place in the die
casting shot sleeve have been noted in this work. Six simulations are provided
in this section; 2 each, one for laminar and one with turbulence, for three
different numbers of mesh. The total number of mesh used are 2,244, 24,000,
and 60,000 cells in the same shot sleeve described in the introduction
to this section.
Simulation Results
* Plunger velocity = 80cm/s, acceleration time = 0.1 sec,
50% fill, water density and viscosity, No surface tension
* Initial condition : flat free surface (There are no
velocities in the fluid)
1. Mesh : 150*400, Turbulent
2. Mesh : 150*400, Laminar
4. Mesh : 80*300, Laminar
5. Mesh : 22*102, Turbulent
6. Mesh : 22*102, Laminar
Results and Conclusions:
As the plunger velocity increases, finer mesh size
and/or a greater number of cells are required to obtain wave motions in
keeping with those observed experimentally. Specifically, the larger number
of cells and the incorporation of turbulence in the simulations are required
to produce waves which both reach the top of the shot sleeve at the proper
position or time during plunger movement and cascade in the fashion observed
in the experimental water physical models. With insufficient number of
cells and the lack of turbulence, the simulated waves formed during the
plunger movement do not behave in keeping with the experimentally observed
ones. A 150x400 mesh system and inclusion of the k-e turbulence model appear
to adequately allow simulation of the wave dynamics associated with the
shot sleeve portion of the die casting process.