<p>The cooling of a hot surface by fluid motion has many applications in engineering. For<br />these mixed convective problems, the forced component of fluid motion may be in the direction<br />of the buoyancy vector or it may oppose the buoyancy force. In the present study, the opposing<br />mode is used to study the interaction of inertia and buoyancy forces in a fluid. Both numerical<br />and experimental techniques are used to study the flow in a rectangular cavity of aspect ratio 2.</p> <p>The inlet Reynolds number is varied between 800 and 1300 and the Grasbof number<br />based on the height of the enclosure is varied between 0 and 2.4 X 10¹⁰. The cases considered<br />correspond to Archimedes numbers of approximately 0, 1, 10 and 20.</p> <p>The flow field is observed qualitatively using laser induced fluorescence and a detailed<br />flow field is generated using a laser doppler anemometer. Temperature profiles are found using<br />fine wire thermocouple probes. These detailed measurements may provide a data base for the<br />verification of computer programs used to predict mixed convection as there are no such detailed<br />chita bases in the present literature.</p> <p>Numerical modelling is based on the SIMPLER algorithm with QUICK differencing. The<br />observed flow field indicated that some regions in the cavity were turbulent while other regions<br />were laminar. This observation suggests the necessity of a low Reynolds number turbulence<br />model. In this study, two forms of the low Reynolds number k-ε model are used. In addition,<br />the commercial computational fluid dynamics program, FLUENT, is used to predict the flow.</p> <p>Comparison of the experimental and computational results suggest that for isothermal and buoyancy dominated flow cases the computational modelling is adequate. Difficulties arise in the prediction of the intermediate Archimedes number cases as the predicted flow is dominated by<br />buoyancy while the experiments show more of a balance. Sources for this discrepancy are<br />discussed.</p> / Doctor of Philosophy (PhD)

<p>This thesis is concerned with experimental study of the drag coefficient of tethered spheres in a vertical pipeline of approximately 0.05 m diameter using water and dilute polymer solutions.</p> <p>Experiments were conducted using four different sphere-to-tube diameter ratios ranging from 0.439 to 0.87. The liquid velocities as well as the associated drag forces and pressure drops were measured, which enabled both the drag coefficients and pressure functions to be computed.</p> <p>Semi-empirical correlations were obtained for the drag coefficient and the pressure function in the range of tube Reynolds number of 3.9 x 10³ to 9.2 x 10⁴.</p> <p>In the experiments using Reten 423 for the diluted polymer solutions, it was observed that a maximized drag reduction would occur at concentration of about 24 wppm for spheres of d/D > 0.74. Drag reductions of up to 60% were obtained which are of a higher order of magnitude than that for non-tethered spheres which has been previously observed.</p> / Master of Engineering (ME)

<p>The problem of highway traffic noise in conjunction with the noise levels produced by aircraft overflight in the vicinity of a general aviation airport is studied. The Toronto-Buttonville airport has been examined and specific examples to illustrate the influence of surface traffic moving along two arterial roadways, the Queen's Highway No. 7 and the regional road Woodbine Avenue, on the noise levels in the vicinity of the airport.</p> <p>Based on actual measurements for both air and surface traffic and utilizing predicted increases for the year 1980, the results from both sound sources have been analysed, combined and presented in the form of contour lines using computer programs developed in this study.</p> / Master of Engineering (ME)

<p>The purpose of this project was to demonstrate the usefulness of optimization in the environment systems field; particularly to improve analytical decision - making techniques for managers.</p> <p>The result was an aid to formulating budgets, in which the social, technical, political and relatively unknown aspects of environmental control systems could be logically compared.</p> <p>Additional benefits, in the area of environmental project evaluations were developed using optimization.</p> / Doctor of Philosophy (PhD)

<p>In this thesis an attempt is made to study the grinding wheel wear phenomena by analyzing the cutting force patterns, wheel wear and wear particles removed from the wheel.</p> <p>Results of measurements of grinding forces and wheel wear, in addition to the scanning electron microscope observations, are presented for grinding hardened M2 tool steel and 52100 bearing steel. Plunge-type surface grinding tests were performed with different grade hardness wheels of aluminum oxide grains in vitrified bond.</p> <p>Contrary to common belief, all wheels tested were found to maintain their grinding capability, during a long grinding operation. The method proposed, for evaluating the performance of grinding wheels from force pattern and grinding wheel wear, appears to present a clear picture of the wear phenomenon. And the method could be adopted for the selection of grinding wheels.</p> / Master of Engineering (ME)

Compared with traditionallaparoscopic surgery, robot-assisted surgery can return<br />all six degrees of freedom (DOF) to the surgeon, provide stereovision, filter tremors and increase precision for positioning and manoeuvring the surgical instruments. The<br />instruments used with commercially available surgical robots use external actuation in the form of relatively large motors located outside the patient with a cable transmission<br />system to bring rotation to the instrument's wrist. The goal of this research is to shift<br />away from the external actuation and design a surgical instrument that is internally<br />actuated. This is expected to miniaturize the overall device, enable instruments to be<br />created with a greater number of DOF than possible using the cable-driven approach,<br />enable the creation of modular designs with a "plug and play" capability and increase the precision ofposition and force control.<br />A novel internally-actuated instrument has been designed and prototyped using 6<br />mm DC motors and miniature transmissions. It features four DOF: an elbow joint, a roll<br />joint, and a wrist joint that employs two independently-actuated gripper jaws to allow for both rotation and grasping ability. The elbow joint is a unique feature that helps to avoid collisions with internal organs.<br />The design of the instrument has been explored in detail. After outlining the target<br />specifications of the device, justification is provided for the selection of the DC motors.<br />Additionally, the thermal properties of the motors have been examined to determine safe current limits. The design of the transmission mechanism (lead screw plus slider-crank) has been analysed and an optimization algorithm for the slider-crank parameters has been developed. Design calculations have been conducted to analyse the kinematics and static loading of the device and finite element analysis (FEA) has been executed to determine the stress concentrations due to the loading. Justification is also given for the component and material selection.<br />A prototype intended as a kinematic model has been manufactured and<br />assembled. The speed performance of the prototype has been tested using two methods: the first used video motion analysis to determine the average speeds of the elbow, roll and wrist joints; the second utilized a potentiometer to measure the instantaneous speed profile across the range of elbow joint motion. Overall, the elbow joint operated at an average speed of 2.0 rpm, the roll joint operated at 40 rpm, and the gripper jaws in the wrist operated at around 3.8 rpm. The potentiometer tests revealed that the joint performed in accordance with the theoretical speed profile, particularly when a correction factor was applied to account for the actual current that was drawn by the motor.<br />A force experiment was also conducted to confirm the torque capabilities of the<br />miniature brushed DC motor used in the prototype. Results showed that the motor,<br />attached to the lead screw and slider components of the elbow joint mechanism,<br />performed at about 15% efficiency. The motor was able to supply a torque of up to 4.2<br />mNm while maintaining an acceptable current level to avoid over-heating. / Master of Applied Science (MASc)

<p>The thesis commences by tracing the underlying research work that established the feasibility and technically justified the current programmes for the development of the implantable artificial heart, more particularly those programmes based upon the use of a heat engine as the power unit of the artificial heart.</p> <p>The provision of a heat source for the heat engine, whether it be a continuously generating source, such as a mass of a suitable radioisotope, or a thermally rechargeable material, adds to the burden of weight and bulk that the user must carry. This inconvenience could be reduced if the thermal efficiency of the engine can be increased. Thus, in the light of a heavy and probably an unending and continuously increasing demand for a practicable artificial heart the author considers that further work is justified if the engine efficiency can be raised, albeit by only a small amount.</p> <p>The author's main endeavour is to identify an ideal engine cycle that appears to promise the most likelihood of high efficiency. It seems remarkable that there is little record of similar investigations readily available in the literature, and therefore, the present author has taken the approach to develop and evaluate parameters for a number of ideal cycles: Carnot, Stirling, Ericsson and the regenerative Otto cycle. The parameters for these cycles are compared, together with the published results for the Thermocompressor, the Schmidt isothermal and the Schmidt adiabatic cycles.</p> <p>Working fluid mass distribution between the hot and cold spaces of the Schmidt isothermal engine is investigated, revealing the low utilization of the working fluid when large dead volumes occur in the engine. The hot volume versus cold volume relationships of the Schmidt and rhombic drive engines are analyzed and compared with the relationship for the true Stirling cycle.</p> <p>Illustrations of the arrangement principles of historical and current "Stirling" engines, as well as the constructions of contemporary artificial heart engines are presented to indicate how problems of arrangement have been answered.</p> <p>The main findings are:</p> <p>(a) Of the isothermal cycles considered, i.e. cycles of potential Carnot efficiency, the true Stirling cycle is significantly the best and better than the adiabatic cycles.</p> <p>(b) The ideal adiabatic cycles achieve efficiencies tending to the Carnot level as the compression ratio tends to unity. Working fluid utilization is least when the ideal efficiency is maximum, that is at unity compression ratio. Inevitable losses in the practical engine indicate that the maximum efficiency will be attained at a compression ratio significantly greater than unity.</p> <p>(c) The effect of regenerator inefficiency in the Stirling engine can be partly compensated by increasing the compression ratio.</p> <p>(d) The hot space-cold space relationships of the Schmidt and rhombic drive engines deviate significantly from those of the ideal Stirling cycle.</p> <p>It is concluded that an engine built to run as closely as possible to the true Stirling cycle is the most promising route to the best attainable efficiency, also that in practice the compression ratio is likely to strongly influence the achievable efficiency.</p> <p>The author recommends building an initial research engine with its hot-cold spatial relationships cam controlled to the requirements of the true Stirling cycle, also to be adjustable for comrpession ratio. The major purpose of this initial engine would be to prove the veracity or otherwise of the cycle selection and to determine how the efficiency varies in practice with compression ratio. For comparison, cams would also be made to stimulate other cycles, e.g. the Schmidt cycle. Suggestions are given for features that would facilitate the operation and performance measurement of the engine.</p> <p>In presenting this work the author also considers that he has compiled a useful bibliography which contains the more pertinent references in the field.</p> / Master of Engineering (ME)

<p>The highly unsteady free surface flow around a rowing oar blade in motion is<br />investigated using modelling techniques. The ability of the numerical model to replicate<br />this complex flow is demonstrated by using computational fluid dynamics (CFD) to<br />simulate previously performed steady-state experiments involving a qum1er-scale rowing blade in a water flume. A comparison of drag and lift coefficients from the experiments and the simulations reveals excellent agreement, providing confidence in the numerical model to handle similar flow conditions. The computational domain is then expanded to simulate a full-scale blade in open water conditions, and steady-state drag and lift coefficients are compared to those previously simulated for a qum1er-scale blade in a flume, revealing substantial differences in magnitude. The computational domain is then modified to allow for oar rotation, as in actual rowing. A force-based rowing model is derived, calculating the instantaneous velocity of a shell based on the propulsive force generated by the motion of the oar blade in the water, the hydrodynamic drag on the shell, and the motion of the rowers within the shell. Using the shell velocity and a prescribed oar angular velocity, the CFD model calculates the highly unsteady blade flow, providing instantaneous drag, lift, and propulsive forces on the blade, in tum driving the rowing model.</p> <p>The dynamic blade-water interaction is depicted in six distinct flow regimes,<br />characterized by the relative motion of the blade in the water and the temporal influence of drag and lift. It is seen that the propulsive force generated by the blade is largely liftinduced through the first half of the stroke. During the middle of the stroke, drag increasingly influences the propulsive force. At end of the stroke, the propulsive force is once again largely lift-induced.</p> / Master of Applied Science (MASc)

<p>The major advantage of the Powder Metallurgical (P/M) manufacturing<br />process is its ability to shape powder directly into a final component form with a<br />primary goal of a high quality, homogeneity of density and mechanical properties<br />and productivity. In this research, powder die filling, powder transfer and powder<br />compaction process have been studied in succession using a novel experimental<br />set-up that utilizes a high strength transparent wall section to observe and record<br />the particle movement and powder compaction during the entire sequence<br />leading up to the formation of a green part. The natural powder pattern itself, as<br />observed from the transparent wall section, is utilized for obtaining full-field<br />displacement and strain measurement for the first time. This strain field data is<br />converted into density distribution data and is validated through other commonly<br />used density measurement methods. The test set-up and the strain<br />measurement technique offer a means of quickly obtaining density distribution<br />data in select cases. In addition to the above, several powder flow characteristics<br />during die filling, powder transfer and powder compaction under a range of test<br />conditions have been noted through a series of high-speed photographic<br />recordings. The role of transfer speed and friction in the development of density<br />gradient and crack formation has been experimentally assessed. Another new<br />method of density measurement based on surface roughness of the compact has<br />been investigated. Finally, powder compaction simulations of the lab-based<br />experiments have been carried out using modified Drucker-Prager Cap model<br />within the ABAQUS CAE. The simulation results are in good agreement with<br />experimental data.</p> / Master of Applied Science (MASc)

<p>Thermal performance of a cooling system for a small sea led computer is investigated. The cooling system consisted of a heat pipe unit which transfers heat from the CPU and northbridge chip to the case wall which had vertical fin channels mounted on the outside. Natural convection and radi at ion moved the heat from the fin plate to the surroundings. An initial benchmarking experiment determined the temperature drop across each component in the system and identi fied th e areas of focus for further research.</p> <p>The heat pipe unit was se lected for initial analysis based on the benchmarking experiment. Heat pipes with sintered wick and grooved wick structures were tested at different orientations with respect to gravity. Gravity was found to cause failure of the groove wick heat pipe in certain orientations while the sintered wick was able to function adequately in any orientation.</p> <p>Carbon foam is a new material with the potential for very high thermal conductivity, 2-3 times that of copper. Based on the variable performance of heat pipes, carbon foam was investigated as a possible solution. Investigations determined carbon foam had thermal conductivity in the range 30-130 W/mK, but it had high specific thermal conductivity, over fo ur times that of copper which means it could be useful in applications that are weight sensitive.</p> <p>Literature research was conducted on the topic of rectangular channel fin perfo rmance and an analytical model was found to estimate performance for different fin geometries. A radiation shape factor equation for rectangular channel fins was also found. Together the models were used to estimate the best fin geometry to maximize natural convection and radiation heat transfer. Heat spreading in the fin plate was investigated using numerical simulation validated by the analytical models and previous studies of similar geometries.</p> <p>A system model is developed to combine the temperature drops of all components of the system to quickly determine the affect of changing one parameter on the temperature of the CPU. Notable results include the highest power CPU that can be used in the current system, the highest surrounding temperature that a 35 W CPU can run in and the size of fin plate needed to run a 65 W CPU in a 40°C environment.</p> / Master of Applied Science (MASc)