Mechanical Engineering - Theses
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ItemEffects of rotation on turbulent boundary layers and wakes( 1986)This work describes experiments of two simple flow cases with imposed system rotation. The first flow is a boundary layer that develops on the flat vertical side-wall of the working section. A trip-wire causes transition, so that the flow in the boundary layer is fully turbulent. The opposite side-wall has been adjusted so that the pressure gradient is zero. The axis of rotation is parallel to the span of the vertical side-wall. The rotation affects the boundary layers; depending on the direction of rotation the changes can be seen as caused by a stabilisation or destabilisation of the flow. A number of mean flow and turbulence data measured with dynamically calibrated hot-wires are presented, both measured as ordinary boundary-layer profiles and, in the presence of 3-dimensionalities, as contour plots. Similarities between the stabilising/destabilising effects of rotation and density stratification, and also curvature, are pointed out. The second flow is the turbulent wake behind a circular cylinder. Each model used in the study is suspended in the middle of the free stream of the working section, with its axis parallel to the axis of rotation. Since the effects of rotation are found to be negligible close to the cylinder, the wake has been followed for several hundred diameters downstream. There the two initially symmetric sides of the wake have grown asymmetric. The observed effects of rotation are explained in terms of transport equations and alternatively by a qualitative model based on assumed structures underlying the turbulence and their behaviour when subject to rotation.
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ItemMotorcycle rider skill assessment( 1983)To determine the differences between the control strategies of skilled and less-skilled riders as they control the lateral and longitudinal motion of a motorcycle, a study of motorcycle handling skills and their assessment was carried out. For the experiments, an instrumented motorcycle was developed which allowed the recording of the various rider/cycle control and response variables while skill tests were being conducted. Riders with a range of riding skills performed a standard skill test and an alternative skill test on the instrumented motorcycle. The experimental data were extensively examined and differences in the control behaviour over the range of riding skills were identified and quantified. A theoretical model was developed describing how less-skilled riders may control the lateral motion of their motorcycle.
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ItemLow-Reynolds-number turbulent boundary layers( 1988-12)This thesis documents an extensive experimental investigation into low-Reynolds-number turbulent boundary layers flowing over a smooth flat surface in nominally zero pressure gradients. The way in which these layers are affected by variations in R(theta), i.e. the Reynolds number based on the boundary-layer momentum thickness, type of tripping device used and variations in freestream velocity, each considered independently, are investigated.
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ItemThe influence of gold-mining on the development of engineering manufacturing in Victoria during the 19th century( 1988)This thesis is a study of how gold-mining contributed to the growth of Victoria's engineering industry prior to 1900. It examines how the demand for the repair and manufacture of mining machinery encouraged local engineering firms to improve their expertise and reputation and to increase their productive capacity. It is argued that the demand for gold-mining machinery provided not only the main initial stimulus for the establishment of the industry during the 1850's and 1860's, but also that it was an important ongoing influence in the later decades of the 19th century, particularly in the non-metropolitan region of Victoria. In the course of this study, extensive use was made of several statistical sources, principally the Statistical Registers of Victoria (for a record of manufacturing establishments and import and export trade), and the Mining Surveyors & Registrars' Statistics (for a record of the quantity of mining machinery employed on the various goldfields). The picture gained from these statistical sources is extended and filled in with descriptive information from newspapers and mining reports which provide a better indication of the effect of technological developments, personal enterprise, and the associations which developed between gold-mining companies and local engineering firms. Ballarat, Castlemaine and Bendigo are identified as the three most important centres in Victoria for the manufacture of mining machinery prior to 1900. However, it is also recognised that a number of important manufacturers existed in Melbourne, and in some smaller country towns such as Clunes, Stawell, Maryborough and Geelong. It is argued that the success of firms in Ballarat, Castlemaine and Bendigo can be largely explained by two factors: the size and continuity of local demand; and the central location of these towns, which minimised the cost of railway freight but still provided convenient access to most of the Victorian goldfields. A discussion of factors such as cost competitiveness, technical innovation, and specialisation of reputation, helps to explain why Victorian firms, both in these towns and elsewhere, came to dominate the supply of mining machinery throughout Victoria by 1900. In the later sections of the thesis, an examination of diversification and the development of export markets explains how the Victorian heavy engineering industry was able to cope with a gradual decline in the demand for mining machinery on many Victorian goldfields after 1875.
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ItemCharles Ruwolt: a history to 1927( 1981)This study is primarily concerned with the working career of Charles Ernest Ruwolt (1873-1946) and with his contributions to windmill and bucket dredge manufacture in Victoria. It continues a programme begun by staff at the University of Melbourne Archives in recording the impressions and recollections of former employees. The aim has been to establish a framework within which these contributions may be placed and from which a company history, freed from error and fiction, may be written. Charles Ruwolt established a foundry and general engineering works at Wangaratta in 1902. What preparation he had for this by way of practical training has been reviewed and shown to be comprehensive both with respect to the products and the processes of manufacture. The various reasons which have been given for his first choice of site are examined and the most probable of these selected. The claims for his windmill, which was the mainstay of his business at first, have also been examined against the background of Victorian and American windmill development up until that time. Although he seems to have sold many of them, there was nothing particularly novel in their construction; his success depending more upon the local nature of his business and the quality of his workmanship. He began manufacturing dredges in 1907 largely as the result of his associations with both Tewkesbury and Stevenson. The partnership arrangements with Stevenson have been described and an examination made of the extent to which Ruwolt’s dredges depended upon New Zealand technology. The number of complete dredges built and the sequence of construction have also been determined. The last complete dredge was ordered in 1921. Ruwolt transferred the business to Richmond in 1913 in order to facilitate the export of tin dredges to Malaya and the diversification of his company's activities from that date has been briefly described.
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ItemA preliminary feasibility study of using salt gradient solar ponds for desalination and other low temperature applications in north eastern Thailand( 1987)A computer model of salt gradient solar ponds has been developed and subsequently used as a tool to investigate the feasibility of using solar pond thermal energy for low temperature applications in North-eastern Thailand. The simulation results obtained indicate that, at 15 % heat extracted yearly, mean temperatures of an unlined uninsulated pond and a lined insulated pond are 67.5 °C and 77 °C respectively. This means that it is practically possible to use solar ponds as a heat source for all normal low temperature applications. Power generation applications are at present likely to prove uneconomic due to the low overall system efficiency estimated at less than 1 %. Modelling has also been evolved for prospective solar desalination systems and used to investigate whether the conventional solar still or a hybrid desalination system(HDS) is the more effective device for desalination applications in the area under consideration. Using these computer models optimum design parameters have been determined for both desalination systems. According to the results obtained from the models, using optimum design parameters as simulation inputs, it was found that the distillation rate of the HDS when supplemented by 15 % heat extracted from the solar pond is in the range of 9 to 11 litres/sq.m day for the unlined uninsulated pond and 12.5 to 15 lltres/sq.m day for the lined insulated pond. These are approximately about 3 or 4.5 times higher than the distillation rate obtained from a conventional solar still. No attempt was made to evaluate the economical feasibility of hybrid desalination systems as compared with conventional solar stills. This was mainly due to the lack of information available on economic considerations for this type of plant in Thailand. Further economic analyses are considered necessary before any firm conclusion can be drawn on which options are the most suitable for desalinating degraded water sources in rural area of Thailand.
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ItemWall shear flows( 1985)A short literature survey outlining recent developments in the modelling of wall turbulence is presented. One of the most recent developments, the A-vortex model of Perry and Chong (1982), which was based on Townsend's (1976) attached eddy hypothesis, is discussed. The use of hot-wires, in particular X-wires, for measuring turbulence quantities, has been found to have several limitations especially over rough surfaces. Some methods of overcoming these shortcomings are proposed, tested and discussed. Mean flow, broad-band turbulence intensity and spectral measurements were carried out over smooth and rough surfaces in zero pressure gradient boundary layers. The spectra measured in the turbulent wall region were found to follow the scaling laws put forward by Perry and Abell (1977) and the A-vortex model of Perry and Chong (1982) for both smooth and rough walls. The A-vortex model of Perry and Chong was used to generate spectral distributions corresponding to some flow cases tested and agreed well with the measured spectral distributions. Strong evidence is presented for the existence of an inertial subrange, where the small scale motions are locally isotropic. The spectral laws put forward by Perry and Abell (1977) are used to infer the broad-band turbulence intensity distributions and reasonable agreement was shown with the measured distributions. The measured broad-band turbulence intensity distributions strongly support the Townsend (1956) Reynolds number similarity hypothesis and the extended form of this hypothesis for rough surfaces of Perry and Abell (1977), at least for the limited range of Reynolds numbers tested here. The results also strongly support the theory that the structure of wall turbulence consists of eddies "attached" to the wall, and that their distribution in the boundary layer follows that proposed in the model of Perry and Chong (1982).
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ItemThe structure of turbulent pipe flow( 1983)A brief literature survey of the modelling of wall turbulence is presented. In addition, a recent development in the modelling of wall turbulence (Perry & Chong 1982) is annotated. The structure of fully-developed turbulent flow in a smooth-walled pipe and in a rough-walled pipe are investigated experimentally over the Reynolds number range of 75,000 to 200,000. Each pipe had a nominal length of 400 diameters. The turbulence intensity results were measured using dynamically calibrated normal and crossed-wires. A dynamic calibration mechanism was built that enabled the wires to be calibrated inside the test section of either pipe. The longitudinal and transverse broad-band turbulence intensity results and their spectral distributions, in the turbulent wall region of both the smooth-walled and rough-walled pipes, show encouraging support for Townsend’s (1976) attached-eddy hypothesis and Perry & Chong’s (1982) model of wall turbulence. Using the spectral similarity laws proposed, the asymptotic longitudinal broad-band turbulence intensity distribution in the turbulent and viscous wall regions of the smooth-walled pipe are predicted with reasonable accuracy. In the core region of both pipes, the longitudinal and transverse spectral results show support for the existence of an inertial-subrange and hence of “locally isotropic” small scale motions. In the smooth-walled pipe, Townsend’s (1956) Reynolds number similarity hypothesis is found to be valid in the asymptotic limit with Reynolds number, while in the rough-walled pipe, the extended version of Townsend’s Reynolds number similarity hypothesis (Perry & Abell, 1977) is not upheld, at least for the results presented in this thesis.
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ItemComputer simulation and practical evaluation of heavy vehicle performance and fuel economy( 1986)This thesis develops and presents optimisation methodology for heavy vehicle performance and fuel economy. The nature of research undertaken involves both computer simulation and practical evaluation. It is believed that these research components will enable the formulation of proposals supportive to the implementation of a heavy vehicle fuel conservation programme. The research commences with a review of heavy vehicle travel and fuel usage statistics relative to those of other road users. Heavy vehicles are then categorised according to their configuration and area of operation. This categorisation, which is based on the Australian Bureau of Statistics 1982 motor vehicle survey, serves as the principle criterion for the development of driving cycles representative of heavy vehicle driving patterns in urban and non-urban areas. Traffic data collection methods and various means for the translation of data into a representative speed-time trace (driving cycle) are reviewed and evaluated. Four comprehensive field surveys conducted over selected routes using an instrumented car to follow and record the driving patterns of targetted heavy vehicles are detailed. Synthesis of four driving cycles follows. These cycles provide means for the study of vehicle performance and fuel economy by giving instructions to a driver or computer on how to operate a vehicle over a given distance or period of time. The application of TARCYC, a comprehensive software package, developed to support data acquisition and reduction, and to implement an enhanced microtrip accumulation technique, is described. It is shown that application of this package leads to the development of very realistic driving cycles with a minimal statistical similarity of 94% to the target data. Vehicle proving ground and highway tests are described. The tests allowed the collection of a large data base for a vehicle with varying configurations. A test procedure providing fuel economy information for a baseline vehicle and for a modified configuration is developed and demonstrated. It is also shown that a repeatability band within 1% is achievable. The equipment and instrumentation used and the computer programs developed for data reduction and processing and for the derivation of such vehicle component characteristics as aerodynamic drag and rolling resistance coefficients are described. An account is given of a novel approach which applies a simulation model in conjunction with curve fitting in coastdown analysis. The procedure and format used in archiving the collected data for future research work is also detailed. Modelling of vehicle performance and fuel consumption, using computer programs, commences with a review of HEVSIM, the US Department of Transport model translated to Fortran 77 and adapted by the author for operation on the University of Melbourne VAX/VMS main-frame computer. The simulation capabilities and limitations of this model are assessed and a critical review of 10 other models is also undertaken. Subsequently, the development of TABESAM, a multi -purpose simulation model which incorporates varying levels of complexity and requires only simple input to provide detailed output, is traced. This model can be used for driving cycle analysis, driver training and motivation, vehicle tests, engine mapping and vehicle component optimisation and has been subjected to experimental validation. When compared with transient and steady state test results, the model shows a prediction accuracy in excess of 95%. The model has been adopted by the Society of Automotive Engineers (SAE-A) for deployment in showroom, point of sale decision making contexts and in the Society’s fuel conservation programme. Finally, and as a result of the practical evaluation and computer simulation of heavy vehicle performance and fuel economy, it is concluded that driver training and motivation, vehicle configuration matching to duty cycle and vehicle component optimisation are essential to fuel conservation. It is also maintained that a heavy vehicle fuel conservation programme depends for its success on the involvement and contributions of government bodies, vehicle designers, city and urban planners and owner/operators.