Impact force of low velocity liquid droplets measured using piezoelectric PVDF film

When a liquid droplet impacts on a solid surface, a transient impact force is developed at the interface between the liquid and the solid surface. Impact velocity, surface tension and density of the liquid are the important parameters that influence the impact force. In the present study, impact forces of two different oils’ droplet (hydraulic oil ISO VG 68 and lubrication oil SAE 30) are compared with the impact force of water droplet. The impact velocity is varied from about 1.38 to 2.96 m/s. The impact force is determined experimentally using polyvinylidene difluoride (PVDF) piezoelectric film attached on the solid surface. The dynamic response of the PVDF piezoelectric film is acquired using data acquisition system with personal computer. The film is dynamically calibrated using bead drop impact method. A linear relationship between voltage output of the PVDF piezoelectric film and impact force is established. The droplet impact force is determined by measuring the voltage output delivered by the PVDF piezoelectric film and converted it into the impact force. Impact forces developed by both the oils’ droplets are lesser than the impact force of water droplet. The impact duration observed is about 600 μs.