# Helmholtz brick¶

This brick represents the complex or real Helmholtz problem:

\[\Delta u + k^2 u = \ldots\]

where \(k\) the wave number is a real or complex value. For a complex
version, a complex model has to be used (see `tests/helmholtz.cc`

).

The function adding a Helmholtz brick to a model is:

```
getfem::add_Helmholtz_brick(md, mim, varname, dataexpr, region);
```

where `varname`

is the variable on which the Helmholtz term is added and
`dataexpr`

is the wave number.