Abstract:
This work describes and demonstrates a novel numerical framework suitable for
simulating the behaviour of freely falling liquid droplets. The specific case studied
is designed such that the properties of the system are similar to those of
raindrops falling through air. The study of raindrops is interesting from both
an engineering standpoint and from a standpoint of pure curiosity. As a natural
phenomenon, rainfall is something which is experienced by everybody, yet
its properties are often misunderstood. The primary engineering application is
in improving the ability of radar to determine the characteristics of rainfall for
meteorological purposes.
The significant original contributions to knowledge within this work come from
several areas. The numerical methods used are a unique combination of a high
order incompressible implicit large eddy simulation method, a conservative level
set method, and a pressure projection method. These methods have all been
implemented on a highly parallel GPU architecture, with a resulting performance
increase of approximately ten times when a single GPU was compared to a single
CPU core.
The water droplets were simulated in a regime not previously studied by three
dimensional methods. The results of these simulations confirmed the validity of
the numerical model by reproducing several important experimental results. New
insight was then gained regarding the behaviour of droplet wakes, an area with
little previous research. The results of the test simulations show great promise
for future use of the numerical framework developed. While the simulations todate
have been of air-water interactions, there is little reason the model should
be constrained to such a system. In theory almost any low speed isothermal
interaction of immiscible Newtonain fluids, with length scales of greater than
1mm, could be modeled accurately by these methods.
