capillary wave and initial spreading velocity at impact of drop onto a surface

The capillary wave and initial spreading velocity in the spreading phase of drop impacting on a glass surface are studied experimentally, while the drop photos are obtained by using a high-speed video camera, which can catch up to 9000 images per second with an exposure time of 4 μs. a wide range of impact velocities are studied by varying the fall height, showing different capillary waves. all attention is given to the capillary wave and initial spreading velocity of drop. a non-linear relation between the wavelength and the impact velocity is found experimentally. combined with the minimum spreading radius theory, a linear relation between the initial spreading velocity and the impact velocity is acquired.