# Wedge - Boundary Condition

## Wedge - Boundary Condition   Description

Wedge is a boundary condition used for simulating axisymmetric problems, where the computational domain represents a wedge-shaped slice of the axisymmetric geometry. This boundary condition is particularly useful for reducing the complexity and computational cost of simulations involving cylindrical or rotational symmetry.

The pair of patches must be symmetrically adjacent to the coordinate plane. The separation between wedge patch pairs should consist of a single layer of cells. Additionally, the points should appear collocated when viewed from the normal direction of the mid-plane.

## Wedge - Boundary Condition   Understanding Wedge

Below there is an example of "wedge" geometry.

For 2-dimensional axisymmetric cases, such as a cylinder, the geometry is specified as a wedge with a small angle (e.g., 5 degrees) and is 1 cell thick. This wedge runs along the centerline and straddles one of the coordinate planes.

Figure 1. Example of wedge type mesh. Source: Greenshields, et al., (2022)

## Wedge - Boundary Condition   Application & Physical Interpretation

#### Wedge in Rotationally Symmetric Problems

Ideal for problems where the geometry and flow are symmetric around an axis, such as flow through a pipe, nozzles, or around cylindrical objects, Wedge boundary condition always applies to all fluid parameters.

Boundary Condition Set for these applications
PhysicsVelocityPressureThermal TSpeciesTurbulence

Wedge

Wedge

Wedge

Wedge

Wedge

Wedge

## Wedge - Boundary Condition   How to apply Wedge in SimFlow

To define the Wedge boundary condition, after meshing, in the Mesh panel the boundary type must be set to Wedge.

Figure 2. Wedge Boundary Condition SimFlow - Mesh panel

No further actions are necessary (in the Boundary Conditions panel). All the dependent variables will be automatically set to Wedge type.

Figure 3. Wedge Boundary Condition SimFlow

## Wedge - Boundary Condition   Wedge - Alternatives

In this section, we propose boundary conditions that are alternative to Wedge. While they may fulfill similar purposes, they might be better suited for a specific application and provide a better approximation of physical world conditions.

Wedge - Alternatives
Boundary ConditionDescription

Empty

constrain type boundary condition used for 2D and 1D simulations

Symmetry

constrain type boundary condition used for planar patches to represent a symmetry condition

## Wedge - Boundary Condition   Literature

• Greenshields, C. J., Weller, H. G., Notes on Computational Fluid Dynamics: General Principles, 2022