Browsing by Author "Appleyard, J."

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    Computational simulation of freely falling water droplets on graphics processing units
    (Cranfield University, 2013-08) Appleyard, J.; Drikakis, Dimitris
    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.
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    Higher-order CFD and Interface Tracking Methods on Highly-Parallel MPI and GPU systems
    (2011-07-01T00:00:00Z) Appleyard, J.; Drikakis, Dimitris
    A computational investigation of the effects on parallel performance of higher-order accurate schemes was carried out on two different computational systems: a traditional CPU based MPI cluster and a system of four Graphics Processing Units (GPUs) controlled by a single quad-core CPU. The investigation was based on the solution of the level set equations for interface tracking using a High-Order Upstream Central (HOUC) scheme. Different variants of the HOUC scheme were employed together with a 3rd-order TVD Runge-Kutta time integration. An increase in performance of two orders of magnitude was seen when comparing a single CPU core to a single GPU with a greater increase at higher orders of accuracy and at lower precision.