19.8.3. User CEL Example 3: Integrated Quantity Boundary Conditions

 

19.8.3.1. Problem Setup

One application of the integrated quantity functions would be to set a boundary inlet temperature based on some average outflow values from a domain. In this way, you could set up a boundary condition, which acts like a thermostat control for a room. This requires the use of a User CEL Function to set the inflow temperature, and one of the arguments, which is passed to the subroutine, is the average outflow temperature.

 
19.8.3.1.1. Creating the User Function

Further information on creating a User CEL Function in CFX-Pre is available in User Functions in the CFX-Pre User's Guide.

First, you should first create a User Routine with the following settings:

  • Routine Name: INLET T

  • Option: User CEL Function

  • Calling Name: inlet_t

  • Library Name: InletTemperature

  • Library Path: /home/cfxuser/shared_libraries

Next, you should create a User Function with the following settings.

  • Function Name: INLET T

  • User Routine Name: INLET T

  • Argument List: [K], [Pa]

  • Result Units: [K]

In this example, the user subroutine InletTemperature.F is stored in the shared library libInletTemperature.so (the prefix and suffix may vary depending on your platform), which can be found under the /home/cfxuser/shared_libraries/<architecture> directory. The new User CEL Function can now be used to set the feedback loop for the inlet temperature as follows:

  • On the Inlet Boundary Condition Values form set the Heat Transfer option to Static Temperature and enter the expression:

    INLET_T(areaAve(T)@Outflow,areaAve(p)@Outflow)

Note that the integrated quantity is passed into the inlet temperature function as an argument. The CFX-Solver recalculates these values during the coefficient loop so that the value is always up to date. For details, see Boundary Details: Inlet in the CFX-Pre User's Guide.

 

19.8.3.2. User Fortran Routine

The routine InletTemperature.F has the following form (note that this is not a complete routine, the purpose of this example is to demonstrate the quantities that can be passed to the subroutine).

#include "cfx5ext.h"
dllexport(inlet_t)
      SUBROUTINE INLET_T (NLOC,NRET,NARG,RET,ARGS,CRESLT,CZ,DZ,IZ,LZ,RZ)
C
C ------------------------------
C        Argument list
C ------------------------------
      INTEGER NLOC, NRET, NARG
      CHARACTER CRESLT*(*)
      REAL    RET(1:NLOC,1:NRET), ARGS(1:NLOC,1:NARG)
C
C------------------------------------------------------------------
C ‘Static Temperature‘ is stored in RET(1:NLOC,1)
C ‘areaAve(T@Outflow)‘ is stored in ARGS(1:NLOC,1)
C ‘areaAve(p@Outflow)‘ is stored in ARGS(1:NLOC,2)
C------------------------------------------------------------------
C
C ------------------------------
C    Executable statements
C ------------------------------
C
      ...
      END