Subroutine Type

Modeling

Definition

A field subroutine is used to calculate the six component forces/torques and their derivatives for a force field entity.

Use

User-defined field using forces/torques computed in a FIESUB:

<Force_Field

    id                  = "303001"

    i_marker_id         = "30301010"

    j_marker_id         = "30301020"

    body1_id            = "30101"

    body2_id            = "30301"

    usrsub_param_string = "USER(303001)"

    usrsub_dll_name     = "NULL"

 />

Calling Syntax

Fortran

SUBROUTINE FIESUB (ID, TIME, PAR, NPAR, DISP, VELO, DFLAG, IFLAG, FIELD, DFDDIS, DFDVEL)

C

void STDCALL FIESUB (int *id, double *time, double *par, int *npar, double *disp, double *veloint, int *dflag, int *iflag, double *field, double *dfddis, double *dfdvel)

Python

def FIESUB(id, time, par, npar, disp, velo, dflag, iflag):
    return [field, dfddis, dfdvel]

MATLAB

function [field, dfddis, dfdvel] = FIESUB(id, time, par, npar, disp1, velo, dflag, iflag)

Input Arguments

[integer] ID

The field element identifier.

[double precision] TIME

The current simulation time.

[double precision] PAR

An array that contains the constant arguments from the list provided in the user defined statement.

[integer] NPAR

The number of entries in the PAR array.

[double precision] DISP

An array of dimension 6 that contains the transitional/rotational displacements of the I marker with respect to the J marker, expressed in the coordinate system of the J marker.

[double precision] VELO

An array of dimension 6 that contains the translational/rotational velocities of the I marker with respect to the J marker, expressed in the coordinate system of the J marker.

[logical] DFLAG

The differencing flag.

[logical] IFLAG

The initialization flag.

Output Values

[double precision] FIELD

The vector output value of dimension 6 that contains the computed forces/torques.

[double precision] DFDDIS

The vector output value of dimension 6 that contains the derivatives of the six force/torque components with respect to the displacement array.

[double precision] DFDVEL

The vector output value of dimension 6 that contains the derivatives of the six force/torque components with respect to the velocity array.

Example

def FIESUB(id, time, par, npar, disp, velo, dflag, iflag):

    dfddis=[]

    dfdvel=[]

        for i in xrange(6):        

            for j in xrange(6):

                dfddis.append(0.0)

                dfdvel.append(0.0)

    dfddis[0*6+0] = -14037.

    dfddis[1*6+1] = -1049.

    dfddis[2*6+2] = -1049.

    dfddis[3*6+3] = -2120.

    dfddis[4*6+4] = -9358.

    dfddis[5*6+5] = -9358.

        for i in xrange(6):

            for j in xrange(6):

                dfdvel[j*6+i] = 0.1*dfddis[j*6+i]

    d=list(disp);

    d[0] = d[0]-5.0;

    field=[]

        for i in xrange(6):

            field.append(0.0)

            for j in xrange(6):

                field[i] = field[i]+dfddis[j*6+i]*d[j]+dfdvel[j*6+i]*velo[j]

    return [field, dfddis, dfdvel]