Merge branch 'master' of github.com:JamesEMcClure/LBPM-WIA
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============
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Running LBPM
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============
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==============
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LBPM examples
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==============
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There are two main components to running LBPM simulators.
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First is understanding how to launch MPI tasks on your system,
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which depends on the particular implementation of MPI that you are using,
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as well as other details of the local configuration. The second component is
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understanding the LBPM input file structure.
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=============================================
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###############################################################################
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MRT model
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=============================================
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###############################################################################
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The LBPM single fluid model is implemented by combining a multi-relaxation time (MRT) D3Q19
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lattice Boltzmann equation (LBE) to solve for the momentum transport, recovering the Navier-Stokes
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equations to second order based on the Chapman-Enskog expansion. The MRT model is used to assess the
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permeability of digital rock images in either the Darcy or non-Darcy flow regimes.
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A typical command to launch the LBPM color simulator is as follows
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```
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mpirun -np $NUMPROCS lbpm_permeability_simulator input.db
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```
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where ``$NUMPROCS`` is the number of MPI processors to be used and ``input.db`` is
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the name of the input database that provides the simulation parameters.
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Note that the specific syntax to launch MPI tasks may vary depending on your system.
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For additional details please refer to your local system documentation.
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***************************
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Model parameters
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***************************
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The essential model parameters for the color model are
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- ``tau`` -- control the fluid viscosity -- :math:`0.7 < \tau < 1.5`
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****************************
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Model Formulation
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****************************
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****************************
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Example Input File
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****************************
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****************************
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Boundary Conditions
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****************************
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The following external boundary conditions are supported by ``lbpm_permeability_simulator``
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and can be set by setting the ``BC`` key values in the ``Domain`` section of the
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input file database
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- ``BC = 0`` -- fully periodic boundary conditions
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- ``BC = 3`` -- constant pressure boundary condition
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- ``BC = 4`` -- constant volumetric flux boundary condition
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For ``BC = 0`` any mass that exits on one side of the domain will re-enter at the other
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side. If the pore-structure for the image is tight, the mismatch between the inlet and
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outlet can artificially reduce the permeability of the sample due to the blockage of
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flow pathways at the boundary. LBPM includes an internal utility that will reduce the impact
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of the boundary mismatch by eroding the solid labels within the inlet and outlet layers
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(https://doi.org/10.1007/s10596-020-10028-9) to create a mixing layer.
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The number mixing layers to use can be set using the key values in the ``Domain`` section
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of the input database
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- ``InletLayers = 5`` -- set the number of mixing layers to ``5`` voxels at the inlet
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- ``OUtletLayers = 5`` -- set the number of mixing layers to ``5`` voxels at the outlet
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For the other boundary conditions a thin reservoir of fluid (default ``3`` voxels)
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is established at either side of the domain. The inlet is defined as the boundary face
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where ``z = 0`` and the outlet is the boundary face where ``z = nprocz*nz``. By default a
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reservoir of fluid A is established at the inlet and a reservoir of fluid B is established at
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the outlet, each with a default thickness of three voxels. To over-ride the default label at
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the inlet or outlet, the ``Domain`` section of the database may specify the following key values
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- ``InletLayerPhase = 2`` -- establish a reservoir of component B at the inlet
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- ``OutletLayerPhase = 1`` -- establish a reservoir of component A at the outlet
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The multi-relaxation time (MRT) lattice Boltzmann model is constructed to approximate the
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solution of the Navier-Stokes equations.
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