Main Help → All Commands → Diffusion Calculations / MPM Boundary Conditions → ConcentrationFlux
The ConcentrationFlux
command applies concentration or transport fluxes to surfaces near particles (which are expected to be on the surface) in MPM calculations.
It applies a flux to all particles within the shape for a ParticleBC block.
ConcentrationFlux (mode),(face),(style),(value),<(timeOrRes)>,<(phaseStyle)>
where the parameters depend on the type of concentration or transport flux being applied. The two types of flux boundary conditions, which depend on (mode)
, are as follows.
This condition applies a surface concentration or transport flux (in solvent flux units or transport flux with units given below) for transport flux per unit area. A positive value is flux into the material while a negative value is flux out of the material. The parameters are:
(mode)
must be external
to indicate it is an external flux.(face)
specifies the particle surface that is on the edge and has the flux. In 2D, imagine a box around the initial particle. Surfaces 1 to 4 are the four edges of the box in the order bottom, right, top, and left (with normals (0,-1), (1,0), (0,1), and (-1,0)). In 3D, imagine a cube around the initial particle. Surfaces 1 to 4 are same as for 2D (now with normals (0,-1,0), (1,0,0), (0,1,0), and (-1,0,0)), 5 in the bottom z surface (normal = (0,0,-1)), and 6 is the top z surface (normal = (0,0,1)).(style)
specifies the style of the applied flux. The setting depends on two parameters specified by arguments (value)
and (timeOrRes)
. If either argument is not supplied, they are set to zero. Use flux units for (value)
and alt time units for (timeOrRes)
(the units may change depending on the (style) or (phaseStyle) setting).This version calculates the concentration or transport flux (in solvent flux units or transport flux with units given below) from a function of the difference between the particle concentration potential or transport value and an entered bath value. The parameters are:
(mode)
must be coupled
to indicate it is a coupled concentration flux.(face)
must be the boundary face (see above).(style)
must be function
.(value)
must be the function
for the the applied flux. It is entered as a user-defined function of t
and entered as quoted text. At each time step, the variable t
will be replaced by the difference between the particle concentration potential or transport value and the entered reservoir value in parameter #5. The function should evaluate to the desired concentration or transport flux. The function can additionally depend on particle position (x
, y
, z
, D
, T
, R
, or Z
in length units), and/or clockwise particle rotation (q
in radians). Note that because t
is used for particle concentration, a coupled surface flux function cannot depend on time.
Use the optional (phaseStyle)
parameter to set flux for other transport tasks. The options and their flux units are:
(phaseStyle)
parameterTransport flux options other than "solvent" cannot use the (style) = "silent" option. When specifying (phaseStyle)
, the (value)
and (timeOrRes)
parameters are required for alignment; they can entered as 0 if not otherwise needed.