When Design Stage is Critical

Many real-world processes involve actions that are triggered when a certain design stage or any prescribed objective or limitation is reached, independent of real timing. Active Simulation Control is a powerful new feature in the upcoming release of FLOW-3D v11.1 that allows users to decide the course of a simulation depending on the design stage of the process. The motivation behind this new development was to extend the idea of probe-controlled events to general objects in order to make simulation control more flexible and robust, hence the name “Active Simulation Control.”

What Makes Active Simulation Control so Powerful?

Active Simulation Control was developed to give users greater flexibility to control their simulations. The focus of the simulation is shifted from determining the exact real time of triggering an event to controlling the design stage of the process. Users can now set an action to take place whenever a certain objective is attained, be it a certain percentage of fluid, fluid velocity, fluid depth or any variable that can be conceived. Active Simulation Control works using the following simple rules that, combined, provide a flexible and powerful feature to users:

  • A component/object can have multiple probe-controlled events
  • An event can be triggered by multiple probe conditions
  • An event can contain multiple actions

There are more options such as the choice of logic condition between multiple probe conditions. These logic extensions allow the user to accurately and efficiently simulate real-world design stages.

Is this Feature Difficult to Implement?

FLOW-3D allows user to intuitively use the new feature through its graphical users interface. Setting up Active Simulation Control involves a simple two-step process.

  1. Create a probe that records the value of a variable
  2. Set up the event that will be triggered when the value of recorded variable at the probe reaches a certain (or range) of value(s)

Yes, it is that simple!

What Does the New Feature Look Like?

Active simulation control
The Active Simulation Control window pops up from the Events tab (in red ellipse).

This window shows one event that is triggered when History Probe 1 detects that the free-surface elevation is greater than or equal to 221. If that happens then the solver will impart a velocity to the chute gate without any time delay (instantaneous action). Event condition logic allows the user to choose if the action should be triggered when only one of the events happen or any or all. Yet again, very flexible.

Active simulation control window
Active Simulation Control Window

Is There a Detailed Example with Results?

Yes, we have put together an example from the high pressure die casting industry as just one of many examples of how you can use Active Simulation Control. High pressure die casting is the typical process for casting complex, thin-walled parts such as transmission covers, alternator housings and other intricate shapes. In the HPDC process, molten metal is poured into a shot sleeve and a plunger forces the metal into runners that feed the metal into the cavity of the die. A significant challenge in the HPDC process is moving the plunger in such a way that the metal initially begins moving without entraining a significant amount of air. However, once the metal reaches the gates, the plunger is moved very rapidly to atomize the melt and fill the part quickly. This phase is called “transition to fast shot.”


The determination of when the plunger motion should be transitioned to a fast shot varies between different manufacturers but is generally based on a point in time when metal has arrived at all the gates. Active Simulation Control is a great tool for this purpose. In this example, this condition can be detected by placing history probes in the gates and detecting when the fluid fraction at all probes is greater than 0.5. Active Simulation Control automatically detects when transition to fast shot should occur and changes the plunger velocity without requiring the user to analyze the results, determine the appropriate time, and then restarting the simulation.

Events and Actions

In our example, an HPDC simulation of a pump cover is shown. The initial plunger motion is completed using the Barkhudarov method available in Utilities menu under Calculators, Shot Plunger Speed, 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, fast shot phase is automatically initiated.

Another useful feature of Active Simulation Control is the ability to change the output frequency when the fast shot begins to capture the rapid filling sequence once the fast shot begins.

The Results

In the animation above, three views of the filling are shown. 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 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.

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