College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
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.