Computational simulation of freely falling water droplets on graphics processing units

摘要

This work describes and demonstrates a novel numerical framework suitable forsimulating the behaviour of freely falling liquid droplets. The specific case studiedis designed such that the properties of the system are similar to those ofraindrops falling through air. The study of raindrops is interesting from bothan engineering standpoint and from a standpoint of pure curiosity. As a naturalphenomenon, rainfall is something which is experienced by everybody, yetits properties are often misunderstood. The primary engineering application isin improving the ability of radar to determine the characteristics of rainfall formeteorological purposes.The significant original contributions to knowledge within this work come fromseveral areas. The numerical methods used are a unique combination of a highorder incompressible implicit large eddy simulation method, a conservative levelset method, and a pressure projection method. These methods have all beenimplemented on a highly parallel GPU architecture, with a resulting performanceincrease of approximately ten times when a single GPU was compared to a singleCPU core.The water droplets were simulated in a regime not previously studied by threedimensional methods. The results of these simulations confirmed the validity ofthe numerical model by reproducing several important experimental results. Newinsight was then gained regarding the behaviour of droplet wakes, an area withlittle previous research. The results of the test simulations show great promisefor future use of the numerical framework developed. While the simulations todatehave been of air-water interactions, there is little reason the model shouldbe constrained to such a system. In theory almost any low speed isothermalinteraction of immiscible Newtonain fluids, with length scales of greater than1mm, could be modeled accurately by these methods.