pressure_expol Subroutine

public subroutine pressure_expol(me, state, bcBuffer, globBC, levelDesc, tree, nSize, iLevel, sim_time, neigh, layout, fieldProp, varPos, nScalars, varSys, derVarPos, physics, iField, mixture)

Outlet Pressure extrapolation boundary. qVal for this boundary must be 0.0

This is taken from the paper: M. Junk and Z. Yang, Asymptotic Analysis of Lattice Boltzmann Outflow Treatments Commun. Comput. Phys., pp. 1-11, 2011.

This boundary condition prescribes density = 1.0 at outlet by forcing the equlibirium part of $f_i$ in normal direction (equation 3.13a): $$f_i(n+1,j_0) = \left[ F^{eq}_{i}(1,u) + f^{neq}_i \right] (n,j_0)$$ For non-normal direction, $f_i$ is extrapolated from neighrbors by (equation 3.13b): $$f_i(n+1,j_0) = 2f_i(n+1,j_0-n) - f_i(n+1,j_0-2n)$$

Usage:

  boundary_condition = {
    { label = 'outlet',
       kind = 'pressure_expol',
       pressure = 'pressure_out',
    }
  }
  variable = {
    name = 'pressure_out',
    ncomponents = 1,
    vartype = 'st_fun',
    st_fun = 1.0
  }

DISCLAIMER: This BC requires pre-collision PDF from 1st and 2nd neighbor which are not available if those neighbors are boundary halo on different process. So, if you encounter a problem with this BC, please check the domain distribution to verify whether 2 neighbors of boundary elements are in one process. The domain distribution can be changed by shifting the boundary by one element or by changing the origin of bounding cube or by using different number of MPI processes.

This subroutine's interface must match the abstract interface definition boundaryRoutine in bc/mus_bc_header_module.f90 in order to be callable via fnct function pointer.

Arguments