Fluid physics work together with fluid materials. This is where you configure and define how the fluid materials will behave in your simulation. When you click on Fluid Physics, you will find the following settings described below in the properties panel.
Viscous Model
Click on Fluid Physics to view the Viscous Model dropdown in the properties panel.
You can choose from:
RANS (Reynolds-averaged Navier-Stokes)
DES (Detached Eddy simulation)
LES (Large Eddy simulation)
Inviscid flow, governed by the Euler equations
Laminar flow, governed by the Navier-Stokes equations
Turbulence
Click on Fluid Physics to view the Turbulence settings. This is where you can choose and configure Spalart-Allmaras or SST turbulence models. See our Turbulence Models guide for more information.
Note: If you select Laminar flow from the Viscous Model dropdown, Turbulence settings will not show.
Transient Incompressible Fluid Simulations
If you are working with an incompressible fluid, you can set up transient simulations using a constant density.
Find the General section in the simulation control panel and change Time to Transient.
Go to your fluid material in the Materials section and change Density Relationship to Constant Density.
Click on your Fluid Physics and find the Spatial Discretization section in the control panel. We recommend choosing either Default or High Accuracy.
In the same section, find Solution Controls and ensure that Apply Suggestion is set to Default. We recommend leaving this setting as-is.
Next, set up your outputs with the appropriate convergence criteria. We recommend creating an output that targets an absolute density residual on the same order of magnitude as a converged steady state simulation.
If one is not available for similar flow conditions, target a relative density residual below 0.005. Additionally, momentum residuals should be below 0.05.
To set up the recommended residuals:
Find the Outputs > Solution Residuals section and uncheck every box except Mass.
Next to Stopping Condition, click on Stopping Condition 1.
Set Tolerance to 0.005.
Click the + icon next to Outputs and select Global. This will create an output called Solution Residuals 2.
Click on Solution Residuals 2 and check only X-, Y-, and Z-Momentum.
Next to Stopping Condition, click Add.
Set Tolerance for the new stopping condition to 0.05.
Scroll down to find the Max Inner Iterations setting. Some time steps can be more difficult to converge, so we recommend allowing up to 40 inner iterations for the best results.