Implementation of the boundary conditions

  In the present version of the ISNaS incompressible program, the following types of boundary conditions have been implemented.
Boundary conditions for the momentum equations:

Type 1:

Velocity prescribed (Dirichlet boundary condition)

Type 2:

Stress prescribed (Natural boundary condition)

Type 3:

Normal stress and tangential velocity given (Semi natural flow)

Type 4:

Tangential stress and normal velocity given (Slip boundary condition and also symmetry condition)

Boundary conditions for the transport equation are:

Type 1:

Scalar prescribed (Dirichlet boundary condition)

Type 2:

prescribed (Robbins boundary condition)

In the next paragraphs we consider the various boundary conditions separately.
In 2D the notion normal and tangential vector have been defined in a somewhat strange way. For a user the normal vector is defined as the outward normal in the case of a counterclockwise direction and as the inward normal in the case of a clockwise direction. The tangential vector is defined in the direction of the outer boundary. In the program, however, the normal and tangential vector are always defined in the 1 or 2 direction in the computational grid. Hence at the boundary , the normal direction is the direction and tangential direction the direction. At the boundary , the normal direction is and the tangential direction etc.
In the sequel the internal definition will be used.

 
• Prescribed velocities
  • 2D implementation
  • 3D implementation
• Stresses prescribed
  • 2D implementation
  • 3D implementation
• Semi-natural outflow condition
  • 2D implementation
  • 3D implementation
• Slip boundary condition
  • 2D implementation
  • 3D implementation
• Transition of types of boundary conditions
  • 2D implementation
  • 3D implementation
• Treatment of boundary conditions at the corners of the region
  • 2D
  • 3D
    • Edges
• Boundary conditions for the transport equation
• The wall function method