GfsProjectionParams

From Gerris

GfsProjectionParams can be used to tune the Poisson solver (for the MAC projection). Ideally, this should rarely be necessary.

The syntax in parameter files is:

GfsProjectionParams {
   tolerance = 1e-3
   nrelax = 4
   erelax = 1
   minlevel = 0
   nitermax = 100
   nitermin = 1
   omega = 1
}

with

tolerance

the maximum magnitude of the relative change in volume of any cell in one timestep (i.e. the maximum error allowed in local volume/mass conservation).

nrelax

the number of relaxations on the finest level of the multigrid hierarchy.

erelax

the factor by which to multiply the nrelax parameter when going up (i.e. coarser grids) the multigrid hierarchy.

minlevel

the coarsest level to consider in the multigrid hierarchy.

nitermax

the maximum number of iterations of the multigrid before giving up.

nitermin

the minimum number of multigrid iterations.

omega

the over-relaxation parameter.

The default values are those given in the syntax description.

Note that GfsApproxProjectionParams should usually be setup to match GfsProjectionParams.

Examples

• Estimation of the numerical viscosity

  ProjectionParams { tolerance = 1e-6 }

• Estimation of the numerical viscosity with refined box

  ProjectionParams { tolerance = 1e-6 }

• Convergence for a simple periodic problem

  ProjectionParams { tolerance = 1e-6 }

• Convergence for the three-way vortex merging problem

  ProjectionParams { tolerance = 1e-5 }

• Mass conservation with solid boundary

    ProjectionParams { tolerance = 1e-6 }

• Poiseuille flow

    ProjectionParams { tolerance = 1e-6 }

• Momentum conservation for large density ratios

    ProjectionParams { tolerance = 1e-6 }

• Hydrostatic balance with solid boundaries and viscosity

    ProjectionParams { tolerance = 1e-12 }

• Hydrostatic balance with quadratic pressure profile

    ProjectionParams { tolerance = 1e-12 }

• Flow through a divergent channel

    ProjectionParams { tolerance = 1e-6 }

• Circular droplet in equilibrium

  ProjectionParams { tolerance = 1e-6 }

• Axisymmetric spherical droplet in equilibrium

  ProjectionParams { tolerance = 1e-6 }

• Planar capillary waves

  ProjectionParams { tolerance = 1e-6 }

• Air-Water capillary wave

  ProjectionParams { tolerance = 1e-6 }

• Fluids of different densities

  ProjectionParams { tolerance = 1e-6 }

• Pure gravity wave

  ProjectionParams { tolerance = 1e-6 }