Global Conditions for Active Simulation Control

In the first blog in the FLOW-3D CAST v5.0 development series, I will discuss the implementation of Global Conditions for Active Simulation Control. Active Simulation Control was first introduced in FLOW-3D v11.1 and FLOW-3D CAST v4.1 to give users greater control over their simulations in terms of autonomous triggering of actions when appropriate conditions are met during the simulation run. In an earlier blog, all the rules and logic behind Active Simulation Control were discussed. These rules and logic work together to provide a flexible and powerful tool that allows users to accurately and efficiently simulate real-world design stages.

Some real-world applications of active simulation are:

  • Turning on a vent when the pressure at a probe exceeds a specified value
  • Triggering the motion of an object when fluid reaches a probe (e.g., increasing the plunger velocity from slow to fast in high pressure die casting when metal reaches the gates)
  • Controlling the addition of metal in gravity casting to stop pouring after metal reaches a particular height in the pour basin or in the sprue to avoid spilling

Introducing Global Conditions

Most often a condition (or a set of conditions) is shared by multiple events. For example, for a high pressure die cycling simulation, probes are placed at the gates. Once the metal reaches the gates (the condition), the following events are set to be triggered:

  • Increasing the plunger velocity from slow to fast
  • Decreasing the output interval for selected data
  • Decreasing the output interval for history data

To simplify this situation of having multiple events that share conditions, Global Conditions have been added to FLOW-3D CAST v5.0. Global Conditions only need to be defined once. Once a Global Condition is defined, it can be selected to trigger multiple events.

Using the high pressure die casting (HPDC) case as an example, the setup for Active Simulation Control is straightforward. First, the user defines a Global Condition that uses the probes at the gates to detect if the metal reaches the gates. Then for each individual event, the user specifies the use of Global Condition. If any conditions need to be changed later, then only the Global Condition definition can be modified. No changes are needed for each event definition. Using Global Conditions makes it easier to modify shared conditions and to keep the condition definitions consistent.

Pump Cover Simulation

This example illustrates an HPDC simulation of a pump cover. The initial plunger motion is computed to minimize air entrainment. Probes are defined in each of the four gates to monitor the arrival of metal. Once metal has reached all four gates, the fast shot phase is automatically initiated. The output frequency is also modified to capture the rapid filling sequence once the fast shot begins. In the animation, three views of the filling can be seen. In the lower left corner, the full geometry including the part, the runners and gates, and the shot sleeve are visible. A view of just the gates with the probes (red balls) is shown at the bottom. Plots at the top of the screen show the fraction of metal at the probes in the gates and the plunger velocity. Notice that the transition to fast shot automatically occurs when the metal reaches the gates as specified by Global Conditions for Active Simulation Control. A time dial – a unique feature of FlowSight – is shown on the lower right. The dial is useful for indicating the progression of time during fast shot. Once the fast shot begins, the output rate becomes very fast.

Global conditions greatly simplifies the definition of shared conditions by multiple events, reducing the chances of error and inconsistency in shared condition definitions, and easier modifications. The addition of Global Conditions to Active Simulation Control will improve the user experience, and make FLOW-3D CAST a better and more convenient CFD software.

In the next blog, I will discuss the new Heat Transfer Coefficient (HTC) calculator in FLOW-3D CAST v5.0.