Solving the World’s Toughest CFD Problems

High Pressure Die Casting (HPDC) simulations are typically very complex as they include almost all of the possible physical processes including heat transfer, melting/solidification, air entrainment, surface defect tracking, and cavitation. As a result, setting up casting simulations can be quite time intensive and error prone. HPDC Process-oriented Workspaces have been added to FLOW-3D CAST to help users create simulations quickly and free of errors.

HPDC simulations can be categorized by four subprocesses:

  1. Thermal Die Cycling
  2. Filling
  3. Solidification
  4. Cooling

It is common, and usually necessary, to simulate each subprocess separately. For example, first a thermal die cycling simulation will be run and then a filling simulation is created as a restart of that simulation. Moving between the various subprocesses adds additional challenges to the setup process as various physical models need to be turned on or off based on the subprocess being simulated. The process workspace feature facilitates this workflow by automatically applying appropriate settings. For example, for thermal die cycling simulations, the thermal die cycling model is activated, and explicit heat transfer is activated. When this simulation is restarted and the subprocess is set to filling, thermal die cycling is turned off, heat transfer is set to implicit, and the appropriate restart options are applied.

The following are some additional examples of how process workspaces facilitate HPDC simulation setup by applying appropriate physical models and “best practice” settings based on a simulation’s subprocess.

Thermal Penetration Depth

A new solver switch is available to turn thermal penetration in components off and on. The new switch eliminates the need to remove the penetration depth setting for each subcomponent in order to turn the model off. Thermal penetration depth can be used to reduce simulation runtime and memory requirements for filling simulations by determining the depth that heat will penetrate into the mold during the simulation and only activating those computational cells in the solver. Process workspaces turn off thermal penetration for all subprocesses except filling.

FLOW-3D Cast simulation manager

Default Values for Numerical Options

During filling simulations, molten metal commonly splashes in the casting cavity creating small droplets with high velocities. These high velocities can reduce the time step unnecessarily, often resulting in long simulation times. The new process-oriented workspaces ensure that implicit advection with a velocity threshold and fluid fraction cleanup are applied to filling simulations. This ensure that filling simulations are accurate and fast.

Activation of Models

While moving between subprocesses, users can easily forget to activate/deactivate physical models. For example, thermal die cycling should always be turned off for all subprocesses except thermal die cycling. For solidification subprocesses, the microporosity model should be turned on. If these models are not properly set, the user will have to rerun the simulation with the appropriate settings activated. Process-oriented setup ensures that these settings are correct, thereby saving the user precious computational time and costs.

Currently, a process-oriented workspace has only been implemented for the HPDC process, but this development will be extended to other casting processes such as low pressure die casting, gravity casting, and lost foam.

In the upcoming and the last blog on FLOW-3D CAST, I will be covering yet another featured development on the new Die Spray Cooling model.

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