Measuring particle collision rates

Collisions between particles in turbulent flow are important in a variety of natural and industrial processes, including rainfall and combustion. A great deal of work has been done to predict and simulate the interactions between particles, though no one has yet measured collision rates with well-understood uncertainties in such settings. We introduce a new computer algorithm to track particles and measure particle collision rates. We characterize the uncertainty of the method by testing it on synthetic data and then use the new method to measure collision rates of real water droplets in a simple benchtop experiment. In this experiment, we vary the diameters of the droplets between 10 and 300 microns and observe collisions varying the impact parameter between 0 and 1 and the Weber number from 0.1 to 20.