Simulation Control in SimScale

 SimScale's simulation control settings allow you to define various aspects of how your simulation runs. These settings influence factors like accuracy, convergence, computational efficiency, and data output. Here's a breakdown of the key controls you mentioned:

• End Time: This defines the total duration for which you want the simulation to run in the simulated time domain (e.g., seconds for transient simulations).

• Delta t (Δt): Also known as the time step, this controls the increment by which the simulation progresses through time in transient simulations. A smaller Δt improves accuracy but increases computational cost.

• Write Control: This determines how often simulation results are written to the output files.

• Write Interval: This works in conjunction with Write Control. It specifies the frequency of result write-out. You can choose based on:

  • Number of Time Steps: Results are written after a certain number of time steps.
  • Physical Time Interval: Results are written at specific time intervals within the simulation duration.

• Number of Processors: This allows you to utilize parallel processing power by assigning your simulation to a specific number of processors available on the SimScale platform. More processors can speed up the simulation but come at an increased cost.

• Maximum Runtime: This sets a limit on the real wall-clock time the simulation can run for, even if the End Time hasn't been reached. This is helpful to prevent excessively long runs or unexpected behavior.

• Potential Flow Initialization (PFI): This is an initialization technique used specifically for incompressible CFD simulations. It provides an initial guess for the velocity field based on potential flow theory, which can sometimes aid convergence, especially for complex geometries.

• Decompose Algorithm: This setting is relevant for parallel processing on high-performance computing clusters. It defines the algorithm used to partition the computational domain into smaller subdomains for efficient distribution across multiple processors. Different decompose algorithms offer varying levels of efficiency depending on your specific problem and mesh characteristics.

Choosing the Right Settings

The optimal values for these controls depend on your simulation type, mesh quality, desired accuracy, and computational resources available. SimScale offers defaults, but you can adjust them for more control over your simulation. It's recommended to consult SimScale's documentation or support for specific recommendations based on your project.

Here are some additional resources that you might find helpful:

• SimScale Documentation on Simulation Control: [SimScale Simulation Control ON simscale.com]

When to Use Simulation Control Parameters in SimScale

Here's a breakdown of when to use the simulation control parameters you mentioned:

• End Time:

  • Set this based on the physical phenomenon you're simulating and the desired duration of the event. For example, if you're simulating airflow around a building for 10 seconds, set the End Time to 10 seconds.

• Delta t (Δt):

  • Use a smaller Δt for:
    • Capturing high-frequency phenomena (e.g., rapid pressure fluctuations).
    • Achieving higher accuracy, especially for problems with strong transient effects.
  • Use a larger Δt for:
    • Steady-state simulations where capturing every detail of the transient behavior isn't crucial.
    • Reducing computational cost, especially for long simulations.

• Write Control & Write Interval:

  • Balance the need for detailed data with storage limitations and post-processing efficiency.
  • Use a smaller write interval for:
    • Capturing transient details more frequently.
    • Debugging convergence issues by having more data points to analyze.
  • Use a larger write interval for:
    • Reducing storage requirements, especially for long simulations with a large amount of data.

• Number of Processors:

  • Utilize more processors when:
    • Your simulation benefits from parallel processing (highly dependent on the problem type and mesh).
    • You have access to a cluster with sufficient available processors.
  • Consider cost implications as parallel processing often comes with a higher fee on cloud platforms.

• Maximum Runtime:

  • Set this as a safety measure to:
    • Prevent excessively long runs due to unexpected behavior or convergence issues.
    • Manage your cloud computing costs by limiting the maximum resource usage.

• Potential Flow Initialization (PFI):

  • Use PFI when:
    • You're simulating incompressible flow.
    • You encounter convergence difficulties, especially for complex geometries.
    • PFI can provide a good initial guess for the velocity field, aiding convergence.

• Decompose Algorithm:

  • This is primarily relevant for advanced users running simulations on high-performance computing clusters.
  • The optimal algorithm depends on your specific problem and mesh characteristics.
  • Consult SimScale's documentation or support for guidance on choosing the best decompose algorithm for your case.

General Tips

• Start with SimScale's default settings for a baseline.
• Adjust the controls based on your specific simulation goals and available resources.
• Consider the trade-off between accuracy, computational cost, and data output requirements.
• Consult SimScale's documentation or support for specific recommendations based on your simulation setup.

SimulationControl, SimScale,  EndTime,  DeltaT,  Write Control,  Write Interval,  Processors, Maximum Runtime,  Potential Flow Initialization, Decompose Algorithm