Artur J. Jaworski PhD MSc(Eng) DIC CEng FRAeS CMgr FCMI FHEA
Professor in Engineering and Head of School
School of Engineering and Design
College of Technology and Environment, London South Bank University
103 Borough Road, London SE1 0AA, United Kingdom
E: artur.jaworski@lsbu.ac.uk; T: +44(0) 207 815 7502
W: https://researchportal.lsbu.ac.uk/en/persons/artur-jaworski
PhD Projects
Currently Offered PhD Projects
Project descriptions given below are examples of typical PhD topics that can be offered to external applicants. My topics usually fall into areas of Mechanical, Aerospace, Chemical and Process and Instrumentation Engineering and are often multidisciplinary by design. Alternative projects can be developed for individual candidates who are advised to contact me directly at a.jaworski@hud.ac.uk.
Heat Transfer and Fluid Flow Processes in Thermoacoustic Devices
The project aims at conducting a fundamental study of fluid mechanical and heat transfer processes occurring in stacks/regenerators and heat exchangers of thermoacoustic devices. In thermoacoustic devices, a standing/travelling acoustic wave causes the compressible fluid to undergo a thermodynamic cycle very similar to the Stirling cycle. This can potentially be utilised in constructing the next generation of reliable and energy efficient prime movers, refrigerators or heat pumps, without moving parts and using environmentally friendly inert gasses as working fluids. Unfortunately, the correct analysis of the thermoacoustic devices is hindered by the lack of understanding of the fluid mechanics and heat transfer processes which are profoundly affected by the transient and three-dimensional nature of the oscillating compressible flow and its interactions with physical boundaries. The proposed research will focus on investigating these complex phenomena in a purpose-built experimental apparatus, using a range of measurement techniques including Particle Image Velocimetry (PIV), Laser Induced Fluorescence (LIF), Laser Doppler Anemometry (LDA) and hot- and cold-wire measurements, in order to determine the flow characteristics inside representative components of a thermoacoustic device. This work will be complemented by numerical studies where the transport coefficients obtained from experiments can be used to enhance the numerical models of the fluid behaviour to benefit future design procedures. (Industrial relevance: power generation, heat ventilation and air conditioning, refrigeration, manufacturing)
Development of Micro-Thermoacoustic Cooler for Heat Transfer Management in Electronics
This project is in the area of Thermoacoustic Technologies that deal with designing engines and refrigerators (heat pumps) with no moving parts. In refrigerators, an acoustic wave present in a thermoacoustic stack (or regenerator), which can be imagined as a series of narrow passages, imposes pressure and velocity oscillations, with a relative phase difference, enabling the compressible fluid to undergo a thermodynamic cycle similar to the Stirling cycle. This, coupled with appropriately phased heat absorption and release, enables “pumping” heat from the cooler to the hotter end of the stack (or regenerator) with no need for cranks, sliding seals or excess weight normally associated with conventional Stirling machines. A reverse process of establishing an acoustic wave due to the strong temperature gradients in the stack (regenerator) forms a basis for the operation of “thermoacoustic engines” – the useful acoustic power being extracted by the appropriate linear alternators. The aim of this project is to utilise the thermoacoustic principles described above in the design of a miniature thermoacoustic coolers that would be used for localised cooling of electronic components, such as for example computer processors.
Sustainable Refrigeration/Air Conditioning Driven by Solar Energy
Traditional approaches to cooling/refrigeration/air conditioning are commonly based on vapour compression cycles that are driven by electrical input to the compressor. In the age of “environmental sustainability” these have major drawbacks of using as working fluids chemicals that are harmful to the environment and draining the electricity that in some instances may be in short supply. This project will investigate the provision of cooling/refrigeration/air conditioning capabilities for either industrial or domestic applications by using the coupling between solar power driven thermoacoustic engine and a thermoacoustic cooler within a suitable demonstrator. Thermoacoustic technologies utilised here are one of the emerging energy technologies with a significant future potential for providing cost-effective thermodynamic conversion processes. Thermoacoustic effect relies on the energy transfer between a compressible fluid and a solid material in the presence of an acoustic wave and thus allowing for the construction of thermodynamic machines with no moving parts.
Application of Thermoacoustic Stirling Cycle for Electricity Generation using Solar Energy
The provision of cost-effective systems for meeting the distributed electricity generation needs is one of the research and innovation challenges. Here, one of the key requirements is the development of systems that would work for prolonged periods of time without the need of frequent maintenance, and ideally would utilize renewable energy sources such as solar energy. One of the possible technical solutions is the application of the novel emerging technology, with a significant future potential, referred to as “Thermoacoustic Technology”. This offers efficient energy conversion mechanisms without the need for any moving parts. This project will investigate the provision of distributed electricity generation for either industrial or domestic applications by using the coupling between a solar power driven “thermoacoustic engine” (which produces high density acoustic energy out of a solar-thermal input) and an energy converter referred to as a "linear alternator" for producing electrical power from an acoustic input. In general, the underlying thermoacoustic effect relies on the energy transfer between a compressible fluid and a solid material in the presence of an acoustic wave, and produces energy conversion mechanisms similar to those present in Stirling cycles. However, a thermoacoustic cycle is realized without expensive hardware associated with classical Stirling devices. The project will utilize an existing experimental apparatus to demonstrate the application of solar energy input for producing the electrical output in realistic working conditions.
Development of Heat Exchanger Design Strategies for Oscillatory Flows
This project addresses fundamental challenges of designing and optimising heat exchangers to be applied in the oscillatory flow conditions. This type of conditions is common in devices such Stirling engines/coolers or thermoacoustic engines/refrigerators or air conditioning systems. The former are often found in cryogenics applications, the latter could be used as low-cost and low-maintenance technology for solar-driven power generation or air conditioning in the Middle-East. A common feature of such applications is a cyclic flow reversal and the associated hydrodynamic energy transfer, which are an integral part of the underlying thermodynamic cycle. In the classic heat exchanger analysis, the heat transfer correlations are derived for steady flows, but unfortunately these correlations do not work for oscillatory flows and so there is gap in understanding the heat transfer (and fluid flow) processes and lack of reliable design guidelines. This project will focus on a mixture of experimental and modelling approaches to tackle these issues.
Control of Flow Unsteadiness on Swept Wings – Studies of Flow Physics Due to Embedded Synthetic Jet Actuators
Previous work shows that application of an array of synthetic jet actuators, embedded within wing’s lading edges, leads to a significant alteration (reduction) to the buffet excitation levels on the suction side of swept wings arising from the vortex breakdown. While this effect has been extensively documented, little is known about the underlying fluid mechanical processes. It has been hypothesised that the coherent vorticity originating from the orifices of the synthetic jets becomes rolled up within the leading edge vortices and interacts with large scale coherent structures originating from the vortex burst, so that the vortex filaments become kinked and dissipate more quickly than in an un-actuated wing. The proposed project aims at unravelling the flow physics behind these processes by investigating the propagation of coherent structures in the post-breakdown region (in both actuated and un-actuated situation) using either the optical flow diagnostics tool such as flow visualisation, LDA and PIV and/or CFD codes such as Fluent. (Industrial relevance: aerospace)
Studies of Heat Transfer in Anisotropic Materials
This project is in the area of smart materials, one of the hot topics in the modern technology, and concerns the design of novel materials whose thermal characteristics could be controlled by varying the degree of geometrical anisotropy within complex/heterogeneous structures. The application of such materials is desirable in many situations including building insulation, automotive, electronics or defence. One simple arrangement for such smart materials is a suspension of disk-like particles in a liquid. Here, the modifier of system’s thermal properties could be an external field (electrical, magnetic), which could change particle orientation. Such structures could act as “shutters” for various heat transfer mechanisms (radiation, convection and conduction), or could be engineered in such a way that the ratio of one heat transfer mechanism to another could be controlled. The project aims at conducting numerical modelling of such materials in order to develop new concepts in controlling heat transfer processes. (Industrial relevance: energy, building and construction industries, defence)
Unsteady Vortex Dynamics and Vortex Breakdown
This project relates to unsteady aerodynamics of swept wings and in particular addresses a challenging problem of the breakdown of leading-edge vortices. Vortex breakdown degrades the aircraft aerodynamic performance and induces flow field unsteadiness related to its varying location relative to the wing, interaction between port side and starboard side vortex breakdown regions, and generation of large-scale coherent structures causing significant aerodynamic loading. Current hypothesis is that the appearance of vortex breakdown is related to the overall balance of vorticity and the limited ability of the coherent vortex to convect the axial component of vorticity in the downstream direction. As the amount of vorticity continually increases, there comes a point when the excess vorticity can only be convected if the vortex structure changes. The proposed work will address these fundamental issues through wind tunnel experiments on a delta wing model using non-intrusive optical instrumentation and measurements of unsteady surface pressure. (Industrial relevance: aerospace)
Characterization of Heterogeneous Mixtures Using Non-Invasive Measurement Techniques
The proposed research aims at investigating the properties of heterogeneous mixtures which are common in many industries including chemical, oil and gas, pharmaceutical, minerals, food, biotechnology and others. Characterisation of such mixtures is crucial for controlling the industrial processes as well as ensuring high product quality. During the research, suitable non-invasive and on-line measurement techniques, based on the combination of electrical impedance spectroscopy and ultrasonic transmission, will be developed. In the first stage, design and laboratory studies leading to construction of robust sensors to facilitate measurements in a selection of industrially relevant situations will be conducted. The measurements will be validated using independent techniques. The second stage will focus on modelling the propagation of the sensing fields which interrogate the mixtures and their interaction with the dispersions. The modelling will be conducted using a commercial package, FEMLAB, and will lead to construction of mathematical models predicting the sensor behaviour. (Industrial relevance: chemical, bio-technology, process, petroleum, chemical, food and drink)
Experimental Studies of Multiphase Flow in Inclined Pipes
This project relates to the physics of multiphase flows, which are a common occurrence in many industries such as nuclear, chemical, petroleum, minerals or food (some of the examples being gas/oil flows in crude oil extraction processes or steam/water flow in helical heat exchangers). On the fundamental level, the project will attempt to study various flow regimes present in gas-liquid system, in a purpose built flow rig, with particular attention to flows in inclined pipelines. These are still not very well understood as most of the existing work relates to vertical and horizontal configurations. The techniques used to interrogate the flow may include high-speed video, pressure drop measurements, optical (LDA, PIV), electrical (capacitance/resistance) or ultrasonics. It is hoped that this will provide a detailed classification of the flow patterns associated with various flow conditions, fluid properties and pipeline inclinations. On the engineering level, the project will aim at developing criterial correlations, which could be used in future in the design process of industrial installations. In its basic form, the project will suit either mechanical, chemical/process/petroleum or nuclear engineering graduates, that is those who had exposure to thermo-fluids and measurement problems during their undergraduate studies. The problem may be suitably modified to accommodate also IT, signal processing and instrumentation engineers, by taking the focus off the flow itself, and instead contributing to the development of methodologies for flow pattern recognition, measurement and signal processing. (Industrial relevance: petroleum, energy sector, chemical)