Experimental determination of the dispersion relation for spiral waves

We have experimentally measured the dispersion relation of spiral waves in the Belousov-Zhabotinsky reaction in an open spatial reactor, for different concentrations. Appropriate rescaling permits the collapse of all data onto a single line. From this, we infer an analytic form for the dispersion relation, which only depends on two physical quantities. In particular, this relation implies that the ratio between the front velocity of the selected spiral and the isolated front velocity is fixed and equal to 0.62, in agreement with previous results.