DFLUX

User subroutine to define nonuniform distributed flux in a heat transfer or mass diffusion analysis.

User subroutine DFLUX:

can be used to define a nonuniform distributed flux as a function of position, time, temperature, element number, integration point number, etc. in a heat transfer or mass diffusion analysis;
will be called at each flux integration point for each element-based or surface-based (heat transfer only) nonuniform distributed flux definition in the analysis;
ignores any amplitude references that may appear with the associated nonuniform distributed flux definition; and
uses the nodes as flux integration points for first-order heat transfer, first-order coupled temperature-displacement, first-order coupled thermal-electrical-structural, and mass diffusion elements.

This page discusses:

User Subroutine Interface
Variables to Be Defined
Variables Passed in for Information

User Subroutine Interface

      SUBROUTINE DFLUX(FLUX,SOL,KSTEP,KINC,TIME,NOEL,NPT,COORDS,
     1 JLTYP,TEMP,PRESS,SNAME)
C
      INCLUDE 'ABA_PARAM.INC'
C
      DIMENSION FLUX(2), TIME(2), COORDS(3)
      CHARACTER*80 SNAME


      user coding to define FLUX(1) and FLUX(2)


      RETURN
      END

Variables to Be Defined

FLUX(1)

Magnitude of flux flowing into the model at this point. In heat transfer cases the units are JT⁻¹L⁻² for surface fluxes and JT⁻¹L⁻³ for body flux. In transient heat transfer cases where a nondefault amplitude is used to vary the applied fluxes, the time average flux over the time increment must be defined rather than the value at the end of the time increment. In mass diffusion cases the units are PLT⁻¹ for surface fluxes and PT⁻¹ for body flux.

FLUX(1) will be passed into the routine as the magnitude of the flux specified as part of the element-based or surface-based flux definition. If the magnitude is not defined, FLUX(1) will be passed in as zero.

This flux is not available for output purposes.

FLUX(2)

In heat transfer cases $d q / d θ$ , the rate of change of the flux with respect to the temperature at this point. The units are JT⁻¹L⁻² $θ$ ⁻¹ for surface fluxes and JT⁻¹L⁻³ $θ$ ⁻¹ for body flux.

In mass diffusion cases: $d q / d c$ , the rate of change of the flux with respect to the mass concentration at this point. The units are LT⁻¹ for surface fluxes and T⁻¹ for body flux.

The convergence rate during the solution of the nonlinear equations in an increment is improved by defining this value, especially when the flux is a strong function of temperature in heat transfer analysis or concentration in mass diffusion analysis.

Variables Passed in for Information

SOL

Estimated value of the solution variable (temperature in a heat transfer analysis or concentration in a mass diffusion analysis) at this time at this point.

KSTEP

Step number.

KINC

Increment number.

TIME(1)

Current value of step time (defined only in transient analysis).

TIME(2)

Current value of total time (defined only in transient analysis).

NOEL

Element number.

NPT

Integration point number in the element or on the element's surface. The integration scheme depends on whether this is a surface or a body flux.

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.

JLTYP

Identifies the flux type for which this call to DFLUX is being made. The flux type may be a body flux, a surface-based flux, or an element-based surface flux. For element-based surface fluxes, this variable identifies the element face for which this call to DFLUX is being made. This information is useful when several different nonuniform distributed fluxes are being imposed on an element at the same time. See About the Element Library for element face identification. The key is as follows:


JLTYP	Flux type
0	Surface-based flux
1	BFNU
11	S1NU (SNEGNU for heat transfer shells)
12	S2NU (SPOSNU for heat transfer shells)
13	S3NU
14	S4NU
15	S5NU
16	S6NU

TEMP

Current value of temperature at this integration point (defined only for a mass diffusion analysis). Temperature for a heat transfer analysis is passed in as variable SOL.

PRESS

Current value of the equivalent pressure stress at this integration point (defined only for a mass diffusion analysis).

SNAME

Surface name for a surface-based flux definition (JLTYP=0). For a body flux or an element-based surface flux the surface name is passed in as blank.