Boundary conditions

Table of Contents

In the absence of sources and sinks, system behaviour is driven by its boundary conditions. These form a critical aspect of case specification where ill-posed combinations will lead to physically incorrect predictions, and in many cases, solver failure.

Definitions

  • Normal vector points out of the domain
  • Distance from face centre to adjacent cell centre, d
  • Non-orthogonality not included

Used when solving the general transport equation to provide:

  • value at boundary
  • gradient at boundary

OpenFOAM offers a wide range of conditions, grouped according to:

Usage

Boundary conditions are assigned in the boundaryField section of the field files within each time directory for each mesh patch. The format follows:

boundaryField
{
    <mesh patch 1>
    {
        type        <patch type>;
        ...
    }
    <mesh patch 2>
    {
        type        <patch type>;
        ...
    }
    ...
    <mesh patch N>
    {
        type        <patch type>;
        ...
    }
}

Each condition is set in a dictionary given by the name of the underlying mesh patch, according to the type keyword.

Further information