Main Help → All Commands → Poroelasticity Calculations / MPM Boundary Conditions → PorePressureFlux
The PorePressureFlux
command applies pore fluid volum fraction 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.
PorePressureFlux (mode),(face),(style),(value),<(timeOrRes)>
where the parameters depend on the type of pore pressure flux being applied. The two types of flux boundary conditions, which depend on (mode)
, are as follows.
This condition applies a surface flux in pore fluid volume fraction/((length units)^2-sec). 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 pore pressure 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 pore pressure flux. The setting depends on two parameters specified by arguments (value)
and (timeOrRes)
. If either argument is not supplied, they are set to zero. The standard units are pore fluid volume fraction/((length units)^2-sec) for (value)
and alt time units for (timeOrRes)
(but the units may change depending on the (style) setting).This version calculates the pore volume fraction flux from a function of the difference between the particle pore pressure and an entered bath pressure. The parameters are:
(mode)
must be coupled
to indicate it is a coupled pore pressure 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 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 pore pressure and the entered reservoir pore pressure in parameter #5. The function should evaluate to the desired flux in pore fluid volume fraction/((length units)^2-sec). 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).
(timeOrRes)
is the pressure of the surrounding reservoir in pressure units.
Note that because t
is used for particle concentration, a couple surface flux function cannot depend on time.