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Wedge Boundary Condition

The wedge boundary condition (BC) is used in computational fluid dynamics to define an axisymmetric situation, for eg. cylinder. The model and flow must be axisymmetric along a central line such that all physical variables of the flow have the same value and distribution at a given radius for all angles.

This boundary condition is specified by two planes that must be selected on separate sides of the domain (referred to as front and back) on surfaces running along the axis. It works for 2D simulations only.


To simulate a two-dimensional model or flow the geometry needs to be specified as a wedge with a small angle (<5 degrees) and a single cell thickness along the curvature.

2d mesh for wedge boundary condition
Figure 1: An example mesh used for simulating subsonic flows in a de Laval nozzle. The wedge boundary condition will be applied to the front and back (unseen) faces

Readers may also need to assure that the face elements of the mesh on both the selected surfaces are congruent. Such a mesh currently cannot be created in SimScale and hence needs to be locally created and uploaded to the SimScale platform.

Wedge is different from the symmetry boundary condition in the sense that the wedge BC applies the Navier-Stokes equations in cylindrical coordinates whereas the latter applies in cartesian coordinates. One big advantage of wedge is that it allows for the rotational flow around the axis and this is possible only because the fluxes and normal components are not assumed as zero.

Get more insight into this wedge boundary condition with the help of this compressible flow validation case.

Last updated: May 25th, 2021