Physics

Set the physics options for the simulation.

This section contains the following topics:

Gravity Defaults

By default, Discovery adds a gravity condition to your analysis to simulate self-weight, and/or buoyancy effects, for structural and fluid physics respectively. If neither of these are selected, then the gravity specification will have no effect on your simulation

Include self-weight

When enabled, self-weight is simulated in the specified direction of gravity. Including self-weight depends on the density of the material. If the self-weight is negligible in comparison with other forces, you can turn self-weight off by clearing the selection of Include self-weight. Turning on self-weight also means that the gravitational acceleration is used in combination with any added mass inputs.

Include buoyancy

When enabled, buoyancy is simulated within a fluid flow analysis. For fluids, buoyant flow is the most important effect of gravity. Because the force of gravity is proportional to fluid density, buoyant flow can arise whenever the fluid density varies due to the temperature or material specification. The addition of buoyancy simulates natural or free convection, where the fluid density varies in temperature using the Boussinesq approximation. If these effects are not important in your simulation (for example, where the velocity of the fluid is such that buoyancy has little impact), you can turn buoyancy off by clearing the selection of Include buoyancy.

Gravity direction

To specify the direction of the gravity, select the appropriate axis from the Gravity direction dropdown list.

Physics Defaults

Working temperature

Specify the Working temperature value and units.
Fluid-solid interface tolerance

Specify the value for Fluid-solid interface tolerance. If fluid and solid bodies are within this distance, a fluid-solid interface is created for fluid-solid heat transfer simulations. If any thin solid bodies (for example: pipes, insulation) are adjacent to a fluid, consider reducing this distance to not have duplicate interfaces.
Contact borderline for review tool

For Connection Assessment, set the range for connections that should be highlighted as borderline.

Material Defaults

Libraries and Locations

Specify which libraries to use, and their locations.

Access additional materials by connecting to the Granta MI materials databases. To see the settings under Granta MI Materials, select Granta MI materials database under the Material Defaults.
Assignments

Select the default solid, fluid, conducting and dielectric material under Assignments. Restart Discovery or create a new simulation for the new defaults to take effect.

Scoping Defaults

Include imported bodies by default
  • Never: no matter the size of their assembly, the parts will not be automatically included in the physics scope
  • Always: no matter the size of their assembly, all the parts will automatically be included in the physics scope
  • Depending on number. You can also select the slider to choose a number between 0 and 499.
Automatically include new bodies

Click Automatically include new bodies to include all parts into the simulation. This option is ON by default and automatically includes the newly created bodies into the simulation scope.

Suggest QuickScope Automatically

Click Suggest QuickScope automatically to automatically add a new named selection based on the scoped bodies. This option is ON by default.

Solver Settings

Specify the Max number of processors settings to use during solving.

Max number of processors

Choose between Use solver default, Use maximum available or Specify number of cores. For Specify number of cores, indicate the number of cores.

Simulation Options Defaults

Discovery provides default simulation options which you can override. The modified default values can be used for all future simulations. Any changes made to the default settings can be reverted to the original Discovery default values using the Reset Simulation Options Settings button. Note that these options are only applicable in the Refine stage.

Structural

For structural simulations in the Refine stage, you can modify the Solution progression controls settings. When set to Automatic, Discovery automatically adjusts the solution progression based on the physics inputs.

If you choose to Define specific values, you must specify the Initial number of substeps that the solver will use initially. Specify the Minimum number of substeps and the Maximum number of substeps needed.

In addition, with Mesh Metrics (Refine), you can control the default mesh metrics monitored during the solve and specify limits for those metrics. For structural simulations, those include:

  • Element quality (off by default) – lower limit (default 0.05)
  • Jacobian ratio (on by default) – upper limit (default 30)
  • Aspect ratio (off by default) – upper limit (default 20)

Any changes made to the these settings can be reverted to the original Discovery default values using the Reset Mesh Quality Options Defaults button.
Fluid Flow

For fluid flow simulations, Use LiveGX solver is turned on by default. The LiveGX solver leverages GPU solver technology combined with body-fitted meshing to provide both fast and accurate fluid solutions. Select LiveGX CPU mode (restart required) if you want Discovery to use the CPU solver instead. The CPU solver allows you to run larger cases, but it will take more time.

To manage convergence, you can choose the stopping criteria to determine when the problem has converged by selecting one of the Stop on ( (restart recommended) options:
  • Engineering convergence: The engineering quantities of pressure, velocity, and temperature are monitored for each flow condition, and temperature and pressure are monitored for each wall condition. When these monitored quantities have stabilized, the solution will be determined as complete. This option is typically useful if these values are the primary focus of the solution and are unaffected by local areas of turbulent flow. If convergence is not achieved, the solution will stop when the Maximum number of iterations are reached.
  • Numerical convergence: Convergence is determined by examining differences throughout the fluid volume. This is useful if you are interested in the flow within the volume. Enter the Maximum number of iterations, if convergence is not met after this number of iterations, then the simulation will stop. Enter the Target numerical convergence to specify the difference for residual measurements (except energy) allowed between iterations, if the difference is below this level it will be considered as converged. Enter the Target numerical convergence, energy to specify the difference for energy allowed between iterations, if the difference is below this level it will be considered as converged.

When modeling turbulent flow, choose one of the turbulence models as the default Modeling method. Alternatively, if the flow is not turbulent, set the fluid flow modeling method to Laminar. Click here to see more information about each of the turbulence options.

The default Meshing method is Tetrahedra mesh. Depending on the complexity of your model and the solution accuracy you can change the default setting to Polyhedra mesh. Click here to see more information about the two meshing methods.

In addition, with Mesh Metrics (Refine), you can control the default mesh metrics monitored during the solve and specify limits for those metrics.. For fluids simulations, those include:

  • Orthogonal quality (on by default) – lower limit (default 0.1)
  • Skewness (off by default) – upper limit (default 0.95)
  • Aspect ratio (off by default) – upper limit (default 20)

Any changes made to the these settings can be reverted to the original Discovery default values using the Reset Mesh Quality Options Defaults button.

Global Fidelity Defaults

Fidelity multiplier (Explore)

Choose from:

  • Standard is the default recommended setting.
  • Aggressive captures more geometric details for higher fidelity results but also consumes more memory during the solve.
  • Extreme captures more geometric details for higher fidelity results but also consumes more memory during the solve.
  • Custom allows you to enter a multiplier. Numbers greater than 1 (the default) increase fidelity while numbers less than 1 decrease fidelity.

Workflow Options

Test cases for topology optimization in defined variations Test cases for topology optimization in defined variations defines test cases in the Design Variations table rather than specifying multiple simulations. This option is on by default.
Background automation for physics Background automation for physics improves performance of Discovery while resource-heavy physics computations are being performed in background. This option is on by default.
Show fluid-to-fluid interfaces Show fluid-to-fluid interfaces allows you to control the detection distance and visually diagnose the overlapping interfaces or conversely check that the interface does exist where it is expected. Decreasing the detection distance enforces a tighter tolerance for detecting whether faces are touching or not. Using a smaller detection distance usually removes any spurious faces that may be overlapping with another condition or interface. This option is off by default.