The Gravity global feature is automatically added when Include gravity is selected at the interface level in the Physical Model settings. It defines the gravity forces from the Acceleration of gravity value. When a turbulence model that solves for the turbulent kinetic energy, k, is used, the option Include buoyancy-induced turbulence is available. When selected, the Buoyancy contribution is by default set to Automatic from multiphysics. Contributions are only obtained from multiphysics couplings that support buoyancy-induced turbulence, such as Nonisothermal Flow. If the Buoyancy contribution is switched to User defined, a text field for the Turbulent Schmidt number appears. See also Theory for Buoyancy-Induced Turbulence in the CFD Module User’s Guide.

This feature requires a specific license. For a detailed overview of the functionality available in each product visit https://www.comsol.com/products/specifications/.

The Acceleration of gravity (SI unit m/s, default value −gconstez in 2D axial symmetry and 3D and −gconstey in 2D) is used to define the gravity forces. It should be a global quantity.