20.3 Surface Integration

You can compute the area or mass flow rate, or the integral, standard deviation, flow rate, volume flow rate, area-weighted average, flow rate, mass-weighted average, sum, facet average, facet maximum, facet minimum, vertex average, vertex minimum, and vertex maximum for a selected field variable on selected surfaces in the domain. These surfaces are sets of data points created by ANSYS FLUENT for each of the zones in your model, or defined by you using the methods described in this chapter in the separate User's Guide , or by using the Text User Interface, described in this chapter in the separate User's Guide.

The following list provides information on the data reported for the various surface integrals:

• For the vertex average, vertex maximum, and the vertex minimum, ANSYS FLUENT reports the node values of the selected variable on the selected surface.

• For mass flow rate, volume flow rate, and flow rate, ANSYS FLUENT reports the rate. Of these, flow rate is the only one associated with a selected variable. The values used in the computation depend on the kind of surface selected:
  • The face flux values are used for face zone surfaces.

  • The cell values are used for postprocessing surfaces.

• For all other surface integrals, ANSYS FLUENT reports the integral, using values that are appropriate for the particular surface:
  • For face zone surfaces, the face values are used when they are available, that is, when they are calculated by the solver or specified as a boundary condition. Otherwise, the cell values are used. The cell value for noninternal faces (i.e., faces that only have c0 and no c1) is the c0 value. The cell value for internal faces (i.e., faces that have c0 and c1) is the average of the c0 and c1 values.

  • For postprocessing surfaces, the cell values are used. See this section in the separate User's Guide for further details.

Example uses of several types of surface integral reports are given below:

• Area: You can compute the area of a velocity inlet zone, and then estimate the velocity from the mass flow rate:

  
  

  
  

• Area-weighted average: You can find the average value on a solid surface, such as the average heat flux on a heated wall with a specified temperature.

• Mass average: You can find the average value on a surface in the flow, such as average enthalpy at a velocity inlet.

• Mass flow rate: You can compute the mass flow rate through a velocity inlet zone, and then estimate the velocity from the area, as described above.

• Flow rate: To calculate the heat transfer rate through a surface, you can calculate the flow rate of enthalpy.

• Integral: You can use integrals for more complex calculations, which may involve the use of the Custom Field Function Calculator dialog box, described in this section in the separate User's Guide , to calculate a function that requires integral computations (e.g., swirl number).

• Standard deviation: You can find the standard deviation of a specified field variable on a surface, such as enthalpy, viscosity, and velocity.

• Volume flow rate: This will report the volume flow rate through the specified surface.

For information about how ANSYS FLUENT computes surface integrals, see Section  20.3.1. Otherwise, for more information about generating a surface integral report, see this section in the separate User's Guide.