Harmonic generation as a probe of dissipation at a moving contact line

We use the pressure generated by a small-amplitude oscillatory flow to probe the dynamics of moving contact lines. By measuring the Fourier amplitude at harmonics of the applied frequency as a function of the steady-state velocity, we are able to determine the velocity dependence of the excess dissipation caused by the moving contact line. We find that the pressure drop associated with this dissipation scales as a power of the contact-line velocity V as ${\mathit{P}}_{\mathrm{cap}}$∝${\mathit{V}}^{\mathit{x}}$, with x=0.40±0.05. We discuss these results in terms of recent theoretical models.