USETTLING

User subroutine to define the settling velocity field in slurry transport analysis.

User subroutine USETTLING:

can be used in a hydraulic fracturing simulation using slurry to define the settling velocity as a function of position, slurry concentration, effective viscosity, etc.;
will be called at each integration point for each element-based or surface-based slurry flow definition in the analysis; and
assumes by default that the settling velocity vector is defined along the gravity direction but also allows the settling velocity to be defined in a more general way.

This page discusses:

User Subroutine Interface
Variables to Be Defined
Variables That Can Be Updated
Variables Passed in for Information

User Subroutine Interface

      SUBROUTINE USETTLING( KSTEP, KINC, NOEL, NPT, COORDS, NDIR, RHOS,
     1 RHOW, DIAMP, RMINGAPOVERDP, DCRACK, CVN, JTYPEFLUID, CONSK, ALPHA, TAU,
     2 EFFMU, CVTAKENASSOLID, GRAV, VM, VSET, TEMP, FIELD, STATEV, NFIELD,
     3 NSTATV, IVSETDIR, I_ARRAY, NIARRAY, R_ARRAY, NRARRAY, C_ARRAY,
     4 NCARRAY )
C
      INCLUDE 'ABA_PARAM.INC'
C
      DIMENSION VM(2), VSET(3), GRAV(2), COORDS(*)
      DIMENSION FIELD(NFIELD), STATEV(NSTATV)
      DIMENSION I_ARRAY(*), R_ARRAY(*) 
      CHARACTER*80 C_ARRAY(*)
C
      user coding to define VSET


      RETURN
      END

Variables to Be Defined

VSET

Components of the settling velocity vector at this integration point.

When IVSETDIR=1, the components of the settling velocity vector are adjusted to ensure that the settling velocity vector is along the direction of the gravity vector. The magnitude of the vector is preserved. To specify only the settling velocity magnitude, it is recommended that you use VSET(1).

When IVSETDIR=2, you can define all the components of the settling velocity vector in global coordinates. If the settling velocity vector is not parallel to the fracture plane, it will be projected to this plane.

Variables That Can Be Updated

STATEV(NSTATV)

Array containing the user-defined solution-dependent state variables at this point.

IVSETDIR

Set IVSETDIR=1 to indicate that the settling velocity vector components will be adjusted to ensure the vector is along the gravity direction.

Set IVSETDIR=2 to indicate that the settling velocity vector can be defined arbitrarily in global coordinates.

If this value is not defined, it is assumed to be 1.

Variables Passed in for Information

KSTEP

Current step number.

KINC

Current increment number.

NOEL

Element number.

NPT

Integration point number.

COORDS

An array containing the coordinates of this point. These are the current coordinates if geometric nonlinearity is accounted for during the step (see Defining an Analysis); otherwise, the array contains the original coordinates of the point.

NDIR

Number of spatial dimensions at this point.

RHOS

Density of proppant particles.

RHOW

Density of carrier fluid.

DIAMP

Diameter of proppant particles.

RMINGAPOVERDP

Minimum value of the ratio of gap opening to particle diameter $α$ (see Section Controls). Particles can only move into a fracture with a gap opening of at least $α$ times the particle diameter. By default, the minimum ratio $α$ is 1.0.

DCRACK

Crack opening.

CVN

Maximum slurry concentration of the current element.

JTYPEFLUID

JTYPEFLUID=1 for a Newtonian Fluid.

JTYPEFLUID=2 for a Power Law Fluid.

JTYPEFLUID=3 for a Bingham Plastic Fluid.

JTYPEFLUID=4 for a Herschel-Bulkley Fluid.

CONSK

Fluid consistency. This is a material property for defining a power law fluid, a Bingham plastic fluid, or a Herschel-Bulkley fluid.

ALPHA

Power law coefficient. This is a material property for defining a power law fluid or a Herschel-Bulkley fluid.

TAU

Yield stress. This is a material property for defining a Bingham plastic fluid or a Herschel-Bulkley fluid.

EFFMU

Apparent viscosity as a measure of fluid resistance to deformation at a given shear rate. For a Newtonian fluid, it is the fluid viscosity. For a non-Newtonian fluid, Abaqus will compute its value.

CVTAKENASSOLID

Maximum attainable slurry concentration.

GRAV(2)

Gravity vector in local coordinates.

VM(2)

Mean velocity vector of slurry flow in local coordinates.

TEMP

Temperature at the start of the increment.

FIELD(NFIELD)

Array of field variables at the start of the increment.

NIARRAY

Size of array I_ARRAY.

I_ARRAY

Not used.

NRARRAY

Size of array R_ARRAY.

R_ARRAY

Not used.

NCARRAY

Size of array C_ARRAY.

C_ARRAY

Not used.