Engineering: Theses and Dissertations
http://hdl.handle.net/10092/840
2016-06-27T23:44:27ZMathematical modelling of self-propelling, coalescing droplets
http://hdl.handle.net/10092/12381
Mathematical modelling of self-propelling, coalescing droplets
Khodabocus, M. I.
When two Newtonian droplets touch, this can lead to either droplets self-propulsion
or coalescence phenomenon. This subject does not appear to have hitherto formed a
prime subject of attention for combined theoretical and numerical treatment, and is
undertaken in this thesis.
The first part analyses the response of an interface subject to a volatile sol-
vent source driven by an air-blow effect. The volatile solvent effect is taken into
account through the full definition of the surface tension gradient and the air-blow
effect through a vapour pressure gradient model equation. Employing the long-wave
approximation of the coupled Navier-Stokes and advection-difusion equations, the
mathematical description reduces to a degenerate fourth order nonlinear parabolic
h-evolution equation coupled with one Poisson equation and one non-homogeneous
Lagrangian derivative equation. Computing these equations using the COMSOL Mul-
tiphysics software, the results are presented and contrasted with those which would
present themselves had the surface tension gradient been expressed in truncated form
and the vapour pressure gradient disregarded.
The second part treats of the self-propulsion of a miscible bi-droplet system in a
capillary tube. The mathematical framework consists of the two-phase
flow, phase field equation set, an advection-diffusion chemical concentration equation, and clo-
sure relationships relating the surface tension to the chemical concentration. The
numerical experiments are carried out using the COMSOL Multiphysics software.
The dynamical response of the bi-droplet reveals a rectilinear motion of the sys-
tem at early-times and an exponential at late-times. A parametric study shows that
the motion obeys Poiseuille flow at early-times. The results are compared success-
fully with available experimental data, thereby establishing a general mathematical
description of the phenomenon.
The third part proposes a versatile framework to study droplets coalescence phe-
nomenon in an unconfined environment. The framework uses the laminar two-phase flow
moving mesh method coupled with an advection-diffusion equation, and is con-
structed in such a way that upon variations of a single parameter, the computational
domain yields geometries ranging from a mono to a bi-droplet system. Taking advan-
tage of its geometrical properties, a theory is developed which establishes a generic
equation describing the growth of that highly curved meniscus neck in the power-law
regimes. Using the COMSOL Multiphysics software, the model is tested by proving
the leading order laws numerically and illustrating the corresponding coalescence flows.
Finally, the thesis discusses how more complex situations can be derived out of
those four parts for further scientific exploration.
2016-01-01T00:00:00ZShape Optimisation of a 200 mm Axial Fan for Aeroacoustic Noise
http://hdl.handle.net/10092/12349
Shape Optimisation of a 200 mm Axial Fan for Aeroacoustic Noise
Mackay, Ryan
Axial flow fans are often the largest contributor to the noise emitted from commercial
refrigerator systems. This has driven the demand for quieter, yet higher performance
axial flow fans. Turbulent fluid motion and aerodynamic forces interacting with the fan
blades generate noise as the fan rotates. The aerodynamic noise emitted from a fan can
be modelled with varying degrees of accuracy which are typically proportional to the
computational cost. Application of a fan performance model to an optimisation algorithm
can be used to develop new and higher performing fan blades. However, there is
currently no rapid method to generate an optimal fan design of specified performance.
The method developed in this project was experimentally validated and shown to be
able to predict the flow rate accurately; however, the fan noise prediction was unsuccessful.
Noise source identification showed that the dominant fan noise source was
incident turbulence noise which was neglected in the aeroacoustic modelling and explains
the poor noise prediction. Knowing the dominant noise source allows for future
modelling to include all relevant physics which will allow for more accurate modelling
that will increase the performance of axial flow fans and reduce refrigeration noise.
This study also showed that fans with aerofoil blade shapes have superior performance
to fans with cambered plate blades, which are commonly used in commercial refrigerators.
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2016-01-01T00:00:00ZModelling and forecasting the demand for electric energy in New Zealand
http://hdl.handle.net/10092/12333
Modelling and forecasting the demand for electric energy in New Zealand
Turnbull, Malcolm John
This thesis studies the demand for electric energy and ways
of forecasting it, as an aid to the economical design and operation
of electric power systems. An examination of the nature of
consumers demands leads to a two part model of the demand. Long
term growth of demand is shown to be determined by the way
the numbers of appliances owned by consumers increases, while the
short term daily, weekly and seasonal demand fluctuations result
from the way consumers use their appliances. A number of
forecasting methods utilizing this model are studied.
The accuracy of a demand forecast influences the amount of
reserve capacity needed to satisfy a given level of demand with
a specified degree of reliability. A criterion is presented which
determines when a forecast may be considered sufficiently accurate.
Sufficient accuracy is defined in terms of minimizing the costs
of providing the reserve capacity and of improving the accuracy
of the forecasts.
1974-01-01T00:00:00ZAn augmented reality interface for supporting remote insurance claim assessment.
http://hdl.handle.net/10092/12296
An augmented reality interface for supporting remote insurance claim assessment.
Yue, Xiang
In past few years Augmented Reality (AR) technology has been applied to many industries
and proved successful with helping the expansion of businesses. This thesis focuses
on exploring how AR-based remote collaboration be used for supporting insurance claim
processes. Previous research on remote collaboration and video conferencing have been
reviewed. Following an interface design procedure, the final system components was
defined and a remote assessment prototype was developed. It could especially facilitate
the claim assessment timing and help to improve the communication between users. As
a part of the prototype interface, the orientation compass plays a significant role for
decreasing disorientation in remote perception. A formal user study was conducted to
evaluate two different designs of 3D compass. The results of the user study show that
the World-fixed compass has the best overall performance compared to the User-fixed
compass or Without-orientation compass.
2016-01-01T00:00:00Z