26.2 Choosing the Spatial Discretization Scheme

Gradients are needed not only for constructing values of a scalar at the cell faces, but also for computing secondary diffusion terms and velocity derivatives. For more information about the different gradients, see this section in the separate Theory Guide.

The three gradients which are available in ANSYS FLUENT are

• Green-Gauss Cell Based

• Green-Gauss Node Based

• Least Squares Cell Based

The gradient options are selectable from the Gradient drop-down list, in the Solution Methods task page.

Solution Methods

In addition, ANSYS FLUENT allows you to choose the discretization scheme for the convection terms of each governing equation. (Second-order accuracy is automatically used for the viscous terms.) When the pressure-based solver is used, all equations are, by default, solved using the first-order upwind discretization for convection. When the density-based solver is used, the flow equations are solved using the second-order scheme by default, and the other equations use the first-order scheme by default. For a complete description of the discretization schemes available in ANSYS FLUENT, see this section in the separate Theory Guide.

In addition, when you use the pressure-based solver, you can specify the pressure interpolation scheme. For a description of the pressure interpolation schemes available in ANSYS FLUENT, see this section in the separate Theory Guide.