Measurement of free-surface flow velocity using controlled surface waves

The paper describes a non-intrusive velocity measurement method that innovatively combines image velocimetry and fluid mechanics principles to determine the free-surface velocity of a moving liquid. Controlled surface waves are generated at the surface of open-channel channel flows. Subsequently, the wave group propagation is captured on video recordings and processed using image velocimetry procedures. The obtained velocity field combined with the principle of wave superposition allows calculation of the free-surface velocity of the underlying flow. The proof-of-concept experiments described in the paper illustrate that the method accurately measures the free-surface velocities in a variety of flow conditions, and especially important in slow and shallow flows where conventional velocity instrumentation has limited capabilities and accuracy.