GfsSurfaceBc

From Gerris

GfsSurfaceBc is used to set boundary conditions for diffusion and Poisson equations on embedded solid boundaries.

The syntax in parameter files is:

GfsSurfaceBc V TYPE VAL

where V is a variable name, TYPE is a GfsFunction returning either Dirichlet or Neumann and VAL is a GfsFunction giving the value of the boundary condition.

Examples

• Vortex street around a "heated" cylinder

  SurfaceBc T Dirichlet 1

• Boussinesq flow generated by a heated cylinder

  SurfaceBc T Dirichlet 1

• Dirichlet boundary condition

    SurfaceBc P Dirichlet {
	double theta = atan2 (y, x);
	double r2 = x*x + y*y;
	return r2*r2*cos (3.*theta);
    }

• Comparison between the explicit and implicit diffusion schemes

    SurfaceBc T Dirichlet 1

• Creeping Couette flow of Generalised Newtonian fluids

  SurfaceBc U Dirichlet (x*x + y*y > 0.140625 ? 0. : - ay)

  SurfaceBc V Dirichlet (x*x + y*y > 0.140625 ? 0. :   ax)

• Translation of an hexagon in a uniform flow

  SurfaceBc U Dirichlet 1.

• B\'enard--von K\'arm\'an vortex street behind a cylinder translating in a fluid at rest

  SurfaceBc U Dirichlet -1.

• Creeping Couette flow between eccentric cylinders

  SurfaceBc U Dirichlet (x*x + y*y > 1.5*R1*R1 ? 0. : - ay/R1)

  SurfaceBc V Dirichlet (x*x + y*y > 1.5*R1*R1 ? 0. :   ax/R1)

• Flow between eccentric cylinders on a stretched grid

  SurfaceBc U Dirichlet (x*x + y*y > 1.5*R1*R1 ? 0. : - ay/R1)

  SurfaceBc V Dirichlet (x*x + y*y > 1.5*R1*R1 ? 0. :   ax/R1)

• Balance with solid boundaries

    SurfaceBc Phi Dirichlet (y > 0)