Melbourne School of Engineering Department of Mechanical Engineering

Mr King-Wai Poon

Supervisors: A/Prof Andrew Ooi and Dr Matteo Giacobello

This research aims to create a better understanding of the flow past a sphere. This will eventually contribute to achieving a better design in applications such as fuel injection in a combustion engine and chemical processing. Numerical simulations are carried out for the flow past a sphere. In the simulations the sphere is subjected to a rotation in between the limits of streamwise (parallel to the freestream velocity) and spanwise (normal to the freestream) directions. Iso-surfaces of flow structure are calculated and time history of force and moment coefficient is plotted. Simulations have been carried out at Reynolds number base on diameter, ReD, of 100, 250 and 300 and non-dimensional rotation speed, Ω*, in the range 0 to 1. Flow structures are found to be axisymmetric, planar-symmetric, frozen and asymmetric across the range. A flowfield which is steady during streamwise sphere rotation is not necessarily steady under spawise rotation and any angles in between. The opposite also holds true. The effects of the vortices on the force coefficient have also been investigated.

Animation showing iso-surfaces of flow structure for the flow over a sphere at ReD = 300 and rotating at Ω* = 1 at rotation angle of 30˚ to the streamwise direction. Hairpin vortices are observed to form in the near-wake of sphere.  With downsteam evolution these take a most distinct omega-shape.

Supervisor: Dr Michael Brear

The fundamental mechanisms of sound generation in hot and combusting fluid flows are incompletely understood. This has practical consequences for the design of a variety of devices such as aircraft engines and industrial burners, to name a few.

In this project we are studying sound generation by cold, hot and combusting flows using novel extensions to both 'acoustic analogies' and 'disturbance energy corollaries'. These extensions have been developed by the group, and are being applied to several problems. For example, the figure below shows the relative magnitude of entropic and vortical source terms responsible for sound generation in the far field of a turbulent, cold jet. These results were obtained by post-processing simulations obtained by collaborators at Stanford University.

We are also performing our own simulations of sound generation by combusting flows. This work involves collaboration with researchers in France. The aim of this work is to apply the famous acoustic analogy of Lilley to investigate the sound sources in a laminar, premixed flame.

Supervisor: Associate Professor Andrew Wirth

Scheduling is a commonly used method of decision making in complex real world problems. A recent development, on-line scheduling, has attracted attention from a number of researchers. In contrast to off-line scheduling, which assumes that complete knowledge of instances is available beforehand, on-line scheduling algorithms make decisions and learn information dynamically over time. Due to this characteristic, the on-line scheduling paradigm models real scenarios more closely than the earlier studied counterpart. Our research focuses on two problems of on-line scheduling with constraints. One is parallel machine scheduling with a single server, which arises in manufacturing where a robot is shared among several machines. The other problem is parallel processor scheduling with a non-crossing constraint, which derives from port terminal management where cranes serve vessels quayside, subject to some spatial constraints.

Supervisors: Dr Michael Brear and Dr Chris Manzie

Three-way catalysts simultaneously remove unburned hydrocarbons, carbon monoxide and nitrogen oxides from car exhausts. Unfortunately, these catalysts are not effective during the first few minutes after a cold engine start, while their temperature is below their so-called 'light-off' temperature (250-340 degrees Celsius). The goals of my research project include i) development of a monolithic three-way catalyst model, ii) its integration with an existing engine model, iii) conducting optimisation studies to minimise key pollutant emissions and finally iv) development of integrated engine control strategies that minimise pollutant emissions.

The plots indicate the extent to which various species in the exhaust gas have been eliminated after passing through a three-way catalyst under particular operating conditions. The red line represents nitrogen (II) oxide, violet line - slow-oxidising hydrocarbons, green line - fast-oxidising hydrocarbons, blue line - carbon monoxide and black line - hydrogen.