Influence of the fill height of the fluid on cavitation due to sudden acceleration

Cavitation is a phenomenon in fluid dynamics that causes a liquid such as water to evaporate during an instant of low pressure and form so-called cavitation bubbles. This instant of low pressure can be caused by a sudden acceleration or pressure wave. We use the sudden downward acceleration from a piston below a cylindrical column of water to cause cavitation. This apparatus was constructed specifically for this experiment to ensure consistent results. Our goal was to investigate how increasing the fill height of the water column would change the amount of cavitation. Therefore we varied the water column fill heights from 0.5 cm to 74 cm. When the piston suddenly accelerates downward, the adhesion between the piston head and the water is broken and a void is created. We found that for a larger fill height of water a bigger void is formed. This void leads to a force of suction against the downward motion of the piston, thus slowing down the piston. However, we did not achieve reliable results to determine whether the number of cavitation bubbles, which form outside the void, relate to the fill height. Further studies are in progress.