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RESIDUAL_OUTPUT - Residual output controls

Structured Grids

 RESIDUAL_OUTPUT MAX        [NUM num] [FREQUENCY iterfreq] RESIDUAL_OUTPUT STATISTICS [{LINEAR|LOGARITHMIC} nbins] [FREQUENCY iterfreq]

Unstructured Grids

 RESIDUAL_OUTPUT MAX        [NUM num] [FREQUENCY iterfreq] RESIDUAL_OUTPUT STATISTICS [{LINEAR|LOGARITHMIC} nbins] [FREQUENCY iterfreq] RESIDUAL_OUTPUT TYPE       {DQ|RHS|VOLUMERHS} RESIDUAL_OUTPUT TYPE       {ZONAL|GLOBAL}

These keywords may be used to write residual data for individual equations to the list output (.lis) file. All four variations of the RESIDUAL_OUTPUT keyword may appear within the same input data (.dat) file. Each of them is described below.

### Structured Grids

 RESIDUAL_OUTPUT MAX [NUM num] [FREQUENCY iterfreq]

If RESIDUAL_OUTPUT MAX is specified, residuals for each equation will be written every iterfreq iterations at num individual grid points, in descending order of the absolute value of the residual. The defaults for iterfreq and num are 50 and 100, respectively. For structured grids the form of the output for each grid point is

```   *MAXNS*   iter   zone   eq   i   j   k   res
```
and for unstructured grids the form is
```   *MAXNS*   iter   zone   eq   cell   res
```
where

iter Iteration number Zone number Equation number (i.e., 1-5 corresponding to the continuity, x-, y-, and z-momentum, and energy) Grid point indices Cell number Residual

 RESIDUAL_OUTPUT STATISTICS [{LINEAR|LOGARITHMIC} nbins] [FREQUENCY iterfreq]

If RESIDUAL_OUTPUT STATISTICS is specified, residual statistics for each equation will be written every iterfreq iterations. The range of residuals from the minimum to the maximum value will be divided into nbins "bins," distributed either linearly or logarithmically between the two values. The default for iterfreq is 50, and the default number of bins is 10, distributed linearly. The form of the output for each bin is

```   *STATNS*  iter  zone  eq  res_ctr  res_n  res_%
```
where

iter Iteration number Zone number Equation number (i.e., 1-5 corresponding to the continuity, x-, y-, and z-momentum, and energy) Residual value at center of bin Number of grid points with residuals in the bin Percentage of the total number of grid points with residuals in the bin

### Unstructured Grids

 RESIDUAL_OUTPUT MAX [NUM num] [FREQUENCY iterfreq]

Same as the description above for structured grids.

 RESIDUAL_OUTPUT STATISTICS [{LINEAR|LOGARITHMIC} nbins] [FREQUENCY iterfreq]

Same as the description above for structured grids.

 RESIDUAL_OUTPUT TYPE {DQ|RHS|VOLUMERHS}

The RESIDUAL_OUTPUT TYPE keyword provides different options for measuring the convergence of the unstructured solver.

DQ Measures the proposed change (or delta) in the solution variables. Measures the L2 and Linf norms of the flux imbalance of the explicit terms. This is the default setting for the unstructured solver. Similar to RHS, but divides by the cell volume.

The structured solver is not affected by this keyword. The residual it reports is the same as that for DQ.

 RESIDUAL_OUTPUT TYPE {ZONAL|GLOBAL}

The RESIDUAL_OUTPUT TYPE keyword can also be used to control whether the residual is computed on a zonal (default) or global basis. This control option only works for unstructured grids.

Last updated 1 Apr 2016