Experimental verification of Lorentz' linearization procedure for quadratic friction

We present results from laboratory experiments in a 'tidal tank', demonstrating the resonant response of the Helmholtz mode in an almost-enclosed basin. In particular the dependence of the response curve (amplification of the tide in the basin relative to the tidal signal at sea as a function of forcing frequency) on the tidal amplitude due to the nonlinear influence of dissipation is observed. Although Lorentz' linearization procedure for coping with this nonlinear effect was already developed at the beginning of the previous century, quantitative experimental validation in this context has not yet been provided. The experimental results presented in this paper show good agreement with theory.