Encyclopaedia Index

Nett-source print-out in RESULT

The RESULT file contains, below the print-out of the solved and stored variables, a tabulation of the "nett sources" of all the patches which have been used to create sources or boundary conditions.

These nett sources are the sums, for all cells in the patch, of:

CO * ( VAL - VAR ) * "type multiplier"


Moreover, the RESULT file also contains, for each solved-for variable:

  1. the summation of all the positive sources;
  2. the summations of all the negative sources; and
  3. the difference between them, which is to say the whole-domain nett source for the variable.

For mass sources at fixed-pressure boundaries, additional information is provided. As well as the nett mass flow through the boundary, the individual positive (In-flow) and negative (out-flow) flows are reported, as shown in this example:

Nett source of R1 at patch named: OB5 (INLET )  = 5.945001E+00 

Nett source of R1 at patch named: OB6 (OUTLET ) =-5.944975E+00 (Mass Out -6.226088E+00 In 2.811145E-01)

pos. sum=5.945001 neg. sum=-5.944975 nett sum=2.574921E-05 

For the energy equation in temperature form, the average temperature of the inflow and outflow is reported, as here:

Nett source of TEM1 at patch named: OB5 (INLET )  = 1.775355E+04 (Average 1.999991E+01) 

Nett source of TEM1 at patch named: OB6 (OUTLET ) =-1.820721E+04 (Ave Out 2.729029E+01 In 2.000000E+01) 

Nett source of TEM1 at patch named: OC1 (FENCE )  = 5.000002E+02 

pos. sum=1.825355E+04 neg. sum=-1.820721E+04 nett sum=46.341797 

For other scalars, the average value of the scalar in the in- and out-flow stream is reported.

When EGWF (Earth Generated Wall Functions) is active, the nett friction force on each blockage is also reported.

There are three exceptions, namely:

  1. nett sources which are equal to zero (perhaps because CO has been set to zero, are not printed:
  2. sources are also not printed for those patches for which CO has been set to FIXVAL;
  3. when CO has been set to a sufficiently large value that VAL - VAR becomes so small in comparison with VAL and/or VAR themselves that round-off error renders its value doubtful, the nett source is reported as 1.234 .

    Then the user is advised to set CO to a smaller value.

Apart from the physical interest attaching to the nett sources, they also convey valuable information about the extent the which the solution of the equations is adequately converged.

Note that as the pressure forces in the momentum equations are not included in the source sums, the nett sources for momentum are not expected to tend to zero.

Nett Sources have units of mass_per_unit_time * variable. Average values have units of the variable. Typically the units of the sources are: