The function `dispersivity` defined in * https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/examples/1ptracer/spatialparams_tracer.hh#L78 * https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/test/porousmediumflow/1pnc/1p2c/spatialparams.hh#L87 * https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/master/test/porousmediumflow/tracer/constvel/spatialparams.hh#L78 is not used anywhere and should be deleted.