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Documentation

Simulation Control

Under the tree item Simulation control, you can adjust different global properties and parameters regarding the simulation process. All analysis types on the SimScale platform do have some of these properties in common however some of them appear only in certain analysis types.

lists of analysis types available in simscale
Figure 1: Simulation analysis types.

Simulation Control General Settings

For OpenFOAM® and Code_Aster simulations, there are two general settings that can be changed under Simulation control, which are:

  • Number of processors: The number of processors assigned to your simulation.
  • Maximum runtime: The maximum runtime of your simulation in real time. The simulation run stops when it goes beyond this value.

Specific Simulation Control Settings

Find below the specific simulation control settings according to each solver incorporated into SimScale:

OpenFOAM®

Following analysis types are supported by OpenFOAM:

  • Incompressible
  • Compressible
  • Convective Heat Transfer
  • Conjugate Heat Transfer
  • Coupled Conjugate Heat Transfer
  • Multiphase

One should find the following control settings:

  • End time: The end time of the simulation.
  • Delta t: Time step size.
  • Adjustable time step: Enables or disables automatic time step adjustments based on specified maximum Courant number.
  • Maximal Courant Number: Maximum value of Courant number allowed. When explicit time integration schemes are used, it should be lower than 1. 0.5-0.7 is a recommended value for most cases.
  • Maximal step: Maximum time step size during runtime.
  • Max alpha co: Defines a Courant number based on the interface velocity.
  • Write control: Algorithm of data generation.
  • Write interval: Frequency of generating data. This is based on the Write control for post-processing.
  • Potential foam initialization: Activates or deactivates the solution of a potential flow field.
  • Decompose algorithm: Algorithm controlling the decomposition of mesh into a number of parts for a parallel run.

Important

For a “Steady-state” analysis, End time value is a ‘pseudo’ time value and holds no physical meaning. It determines the number of overall iterations done to reach a steady-state, calculated as “(end time) / (time step length)”.

Code_Aster

Following analysis types are supported by Code_Aster:

  • Static
  • Dynamic
  • Heat Transfer
  • Themomechanical
  • Frequency Analysis

One should find the following control settings:

Linear analysis

  • Pseudo time stepping: Increments to subdivide the solution into smaller steps that makes it easier to converge.
  • Static time steps: Defines static time step for simulation.

Non-linear and Dynamic analysis

  • Time step definition: Controls how the time step will be defined.
  • Simulation interval: The value for t if the simulation terminates.
  • Maximum time step length: Maximum interval for the calculated time step.
  • Minimum time step length: Minimum time step allowed.
  • Maximum residual: The maximum residual allowed before the simulation fails.
  • Retiming event: Controls the time step adaptation.
  • Time step calculation: Method for time step computation.
  • Additional Newton iterations: Percentage of additional Newton iterations allowed when the simulation has not converged after the maximum number of Newton iterations has been reached.
  • Number of subdivisions: Number of equal subdivisions of a time step in case of adaptation.
  • Max subdivision depth: Maximum depth for time step subdivisions. The simulation stops when it goes over this value. If after a number of n consecutive subdivisions the solution does not converge, it will stop and not do the (n+1)th subdivision.
  • Newton iteration threshold: Threshold for the number of maximum Newton iterations before the time step increases. If the number of Newton iterations required to converge a time step is smaller than this number and the current time increment is smaller than initially defined, the time increment will be increased for the next time step 
  • Time step augmentation: Percentage for time step increment after Newton iteration threshold is reached.
  • Write control definition: Frequency of intermediate results saved.

Pacefish®

Following analysis types are supported by Pacefish:

  • Incompressible (LBM)
  • Pedestrian Wind Comfort (PWC)

One should find the following control settings:

Incompressible (LBM)

  • End time: The end time of the simulation in simulation time.
  • Maximum runtime: The maximum runtime of your simulation in real time. When it goes over this, the simulation run will stop.

Pedestrian Wind Comfort (PWC)

  • Maximum runtime per direction: The maximum runtime of your simulation in real time for each wind direction. The simulation run will stop when it goes over this value.
  • Number of fluid passes: The number of passes the air makes through the domain.

You can find more details and tips on how to control simulation time and timestep in a PWC simulation here.

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