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Old   August 19, 2005, 17:02
Default Normalized residuals
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I would like to know if the error values for the variables printed out by the program at the monitor window represent the normalized residuals for each variable. If so, is the mass residual normalized by the inlet mass flow rate or not?

Thanks in advance.

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Old   August 21, 2005, 04:07
Default Re: Normalized residuals
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Hi, Yes the residuals are normalised, however I dont think by inlet values. however they can be normalised by inlet values.

Question: - How do I convert the residuals obtained with SELREF=T to residuals normalised by reference inflow quantities?


This question is best answered by means of an example, which in this case is taken to be 2d single-phase flow in the y-z plane with solution for mass continuity (P1), momentum (V1 and W1), enthalpy (H1) and mixture fraction (MIXF). Note that in this example the units of 'resref' and 'res sum' for P1 are kg/s rather than m^3/s because DENPCO=T in the Q1 input file.

The conversion procedure is as follows:

Near the bottom of the RESULT file you will find the following normalised residuals printout for the last sweep:

Whole-field residuals before solution with resref values determined by EARTH & resfac= 1.000E-03 variable resref (res sum)/resref

P1 3.718E-09 1.562E+00

V1 7.078E-11 1.819E+02

W1 1.880E-08 6.684E-01

H1 8.555E-03 4.698E-01

MIXF 1.317E-10 5.908E-01

In addition, the following nett source printout is given for all boundary conditions and source terms, including the reference inflow rates of each dependent variable:

Nett source of W1 at patch named: INLETF = 1.202E-06 Nett source of W1 at patch named: INLETA = 2.238E-04 Nett source of W1 at patch named: OUTLET =-5.453E-04 Nett source of W1 at patch named: WFNN =-2.016E-04 nett sum=-5.219E-04 pos. sum= 2.250E-04 neg. sum=-7.470E-04

Nett source of R1 at patch named: INLETF = 2.003E-06 Nett source of R1 at patch named: INLETA = 3.799E-05 Nett source of R1 at patch named: OUTLET =-3.999E-05 nett sum=-3.638E-12 pos. sum= 3.999E-05 neg. sum=-3.999E-05

Nett source of H1 at patch named: INLETF = 9.902E+01 Nett source of H1 at patch named: INLETA = 4.615E+01 Nett source of H1 at patch named: OUTLET =-1.452E+02 nett sum= 2.136E-04 pos. sum= 1.452E+02 neg. sum=-1.452E+02

Nett source of MIXF at patch named: INLETF = 2.003E-06 Nett source of MIXF at patch named: OUTLET =-2.003E-06 nett sum=-6.821E-13 pos. sum= 2.003E-06 neg. sum=-2.003E-06

The actual residuals can be recovered by multiplying the (resref) column by the (res sum)/resref column, as follows:

variable resref (res sum)/resref res sum

P1 3.718E-09 1.562E+00 5.8075E-09 kg/s

V1 7.078E-11 1.819E+02 1.2875E-08 N

W1 1.880E-08 6.684E-01 1.2566E-08 N

H1 8.555E-03 4.698E-01 4.0191e-03 W

MIXF 1.317E-10 5.908E-01 7.7808E-11 kg/s

These 'res sum' values can now be normalised by dividing them by the appropriate reference inflow rates (taken from the Nett source printout), as follows:

variable ref value res sum %error

P1 3.999E-05 5.8075E-09 kg/s 0.0145

V1 2.250E-04 1.2875E-08 N 0.0057

W1 2.250E-04 1.2566E-08 N 0.0056

H1 1.452E+02 4.0191e-03 W 0.0028

MIXF 2.003E-06 7.7808E-11 kg/s 0.0039

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