# udfGetResidualNorm()

Return the current residual norm of requested equation. This value forms the numerator of the residual ratio for the given equation.

## Syntax

conv = udfGetResidualNorm( udfHd, eqnName) ;

## Type

AcuSolve User-Defined Function Global

## Parameters

- udfHd
- The opaque handle (pointer) which was passed to the user function.
- eqnName (integer)
- Symbolic name of the requested equation.
- UDF_EQN_PRESSURE
- Pressure.
- UDF_EQN_VELOCITY
- Velocity.
- UDF_EQN_SPECIES
- Species.
- UDF_EQN_EDDY_VISCOSITY
- Turbulence eddy viscosity.
- UDF_EQN_KINETIC_ENERGY
- Turbulence kinetic energy.
- UDF_EQN_EDDY_FREQUENCY
- Turbulence eddy frequency.
- UDF_EQN_MESH_DISPLACEMENT
- Mesh displacement.
- UDF_EQN_RADIATION
- Radiation.

## Return Value

- conv (real)
- This routine returns a pointer containing the current convergence information. If the requested
convergence information is not available, an assertion is given. The dimension of the returned array depends on eqnName as follows:
eqnName Array Dimension UDF_EQN_PRESSURE 1 UDF_EQN_VELOCITY 1 UDF_EQN_SPECIES udfGetNumSpecs() UDF_EQN_EDDY_VISCOSITY 1 UDF_EQN_KINETIC_ENERGY 1 UDF_EQN_EDDY_FREQUENCY 1 UDF_EQN_MESH_DISLACEMENT 1 UDF_EQN_RADIATION 1

## Description

This routine returns the current convergence level of the residual norm. For
example,

```
Real* conv ;
Real presResNorm;
...
conv = udfGetResidualNorm( udfHd, UDF_EQN_PRESSURE) ;
presResNorm = conv[0];
```

## Errors

This routine expects a valid udfHd and eqnName.