Internal combustion (IC) engines have been the predominant technology for sourcing or generating power for over 100 years. The fundamental function of engines has not changed since there first introduction. By combusting fuel within the chamber causes a pressure build from the expanding gasses pushing the piston assembly through the cylinder, this linear action is then translated to rotation through the crankshaft to generate work. During combustion the gasses will try to move past the piston and into the crankcase, to deter this from occurring piston rings are introduced. Thus rings are designed to be in tight contact to the cylinder wall, and is subject to friction and wear as it travels up and down the cylinder wall. When a new ring pack is introduced, a running-in process is required. This involves running the engine at a variation of speeds for set times, typically defined by the manufacturer. While this procedure is executed the compression ring will undergo a series of thermodynamic morphological stages, the material will change shape due to the heat from the combustion process and suffer material loss due to the friction wear between cylinder wall and ring face. This thesis examines the impact of the running-in method on the compression ring and its performance. The work presented shows a novel numerical method that offers the first simulated solution to compression ring rotation around the piston crown and its impact on the engine performance. This has been achieved by adopting simultaneously two modelling packages to compute dynamics and contact mechanics for a more accurate multiphysics result. Using this model a coating refinement has been developed, offering a new chamfer change to the present ISO standard ensuring a longer coating operational life.

Heat transfer is one of the main phenomena in many industrial processes and applications such as heat exchangers and power generation. For many years, liquids such as water, oil and ethylene glycol had been used as the heat transfer fluids. These fluids have a poor inherent thermal conductivity. Thus, innovation in developing another generation of heat transfer fluids is required for better efficiency. Nanofluids represent a class of pioneering engineering heat transfer fluids. These fluids are made by dispersing metallic or non-metallic particles with nanometer size in various base fluids. With their predominant thermophysical properties, nanofluids are promising medium for heat transfer enhancement of next generation heat dissipation in many industrial applications. This research is focused on studying the enhancement of heat transfer in wall-bounded flows using nanofluids. The enhancement was investigated numerically by modelling nanofluids using CFD technique. Several configurations were tested with different flow types namely, natural convection in a square cavity, forced convection in a backward facing step and flow in micro-channels. The effect of Brownian motion on the heat transfer performance and fluid flow characteristic was investigated for natural convection flow using various nanofluids with different volume fractions for a range of Raleigh numbers. The results showed that the increase in the volume fraction deteriorates the heat transfer. On the other hand, the increase in Ra number promotes the heat transfer rate. For backward facing step, the effect of the inclination angle of the face step using nanofluid was investigated thoroughly. The increase in the facing step angle was found not preferable from a heat transfer perspective, the results showed that the Nu number decreased by up to 3% when 90o inclination angle is tested compared to 125o inclination angle and this information may be valuable for designing industrial equipment. An empirical effective viscosity model is proposed as part of the study. The model is based on available experimental, numerical and theoretical data. The sensitivity of the model has been rigorously scrutinized for different volume fractions and wide range of temperatures. The results showed that the proposed model is reliable and can be employed for various flow configurations. The proposed model has also been used to predict flow through microchannels of various cross-sectional shapes and area. The effect on friction factor for such channels as well as the heat transfer performance has been thoroughly investigated. It was found from this investigation that most of the heat transfer occurred in the U-bend microchannel took place at the downstream flow and it was higher by up to 40.5% compared to the upstream when 6% volume fraction was tested. Finally, a general purpose test rig was designed and built in the lab to conduct some experimental investigation for a double pipe heat exchanger with nanofluids as a coolant. Four different nanoparticles were purchased and are ready for synthesising the nanofluid using ultrasound bath and magnetic stirrer. The rig is ready for the run and several test runs were conducted using water as the base fluid. Unfortunately, due to certain technical extenuating circumstances, experiments using nanofluids could not be conducted within the time span of the project.

The utilisation of composite materials is increasing across many industries, spurred by the need for weight reduction and improved mechanical properties. This has led to an increase in their machining requirements. Although composites are laid in near-net shape, machining processes such as drilling and edge trimming are required to give the composites parts their final geometry and functionality. Machining of composites is challenging due to their low machinability and high cost. Numerical modelling presents a valuable tool for cost reduction and better understanding of the machining processes. Most modelling of machining is carried out using the Finite Element Method, which requires significant time in generating the mesh. Meshfree methods present an attractive choice for machining simulations due to their capabilities in modelling large deformations without the need to construct a mesh. This work aims at developing an efficient meshfree model to simulate orthogonal cutting of unidirectional composites. The Element-Free Galerkin (EFG), which is a prominent meshfree method, is used to construct the model using MATLAB. Steady-state and dynamic models are developed and validated against experimental evidence. The models include several novel features in constitutive relations, composites failure and contact modelling. The main outputs of the simulations are cutting forces and chip formation. Good agreement with experiments is achieved in predicting cutting force. However, thrust force is significantly under-estimated, which is noticed in most of the relevant literature. Three phases of orthogonal cutting experiments are carried out to gain better understanding of the cutting process and generate model validation data. Statistical significance of fibre orientation angle, depth of cut, rake angle and cutting speed on cutting forces and surface integrity is established. Furthermore, the effect of fibre volume fraction on cutting forces is investigated. This work showed that the EFG is a viable numerical method to simulate orthogonal cutting. The simple and automated preprocessing and high quality of approximation are the most advantageous features of the developed model.

Classical techniques for mitigating vibration in rotating structures are divided into three main categories viz. careful design and manufacture, correct installation and effective control strategies. The balancing sleeves analysed in this thesis were developed as a ‘semi active’ method of vibration control to improve the state of balance of dynamically unstable coupling shafts. However, the addition of the balancing sleeves affects the natural dynamics of the shaft, and requires a detailed understanding of their characteristics and the impact on the overall shaft dynamics in order to be useful in practice. As a first approximation, the sleeves are initially modelled as part of a full coupling shaft using the Extended Hamilton’s Principle. The simulation studies show that the flexibility of the sleeves have little impact upon the dynamics of the system and can therefore be neglected. However, when compared to results from the use of computational finite element methods with different sleeve lengths, discrepancies are identified. Experimental validation using a purpose built high speed test facility is used to show that the difference is due to the lack of appropriate modelling of sleeve flexibility characteristics. A full system model using finite element methods is therefore devised. More widely, a study of the impact of sleeve lengths shows that the classical definition of a ‘shaft mode’ does not encompass sufficient fidelity to discriminate between modes that are initially considered as being shaft dominated and those that are considered as sleeve dominated mode shapes, and the sharp transition that occurs between the two. It is notable that the transition between the two dominant modal contributors occurs at sleeve lengths that impart a natural frequency that is close to that corresponding to the shaft. It is concluded that the mechanism of passive control via use of the sleeves is a combination of softening due to the added mass of the sleeves and coherence of the individual modes of the shaft and sleeves. In this way, it is shown that the sleeves act in a manner similar to a tuned mass-damper. By appropriate design therefore, use of balancing sleeves offer the opportunity to increase the critical speed margin in practical applications and reduce unwanted lateral vibrations.

Engineers have been designing machines with long, flexible shafts and dealing with consequential vibration problems, caused by shaft imbalance since the beginning of the industrial revolution in the mid 1800’s. Modern machines still employ balancing techniques based on the Influence Coefficient or Modal Balancing methodologies, that were introduced in the 1930’s and 1950’s, respectively. The research presented in this thesis explores fundamental deficiencies of current trim balancing techniques and investigates novel methods of flexible attachment to provide a component of lateral compliance. Further, a new balancing methodology is established which utilizes trim balance induced bending moments to reduce shaft deflection by the application of compensating balancing sleeves. This methodology aims to create encastre simulation by closely matching the said balancing moments to the fixing moments of an equivalent, encastre mounted shaft. It is therefore significantly different to traditional methods which aim to counter-balance points of residual eccentricity by applying trim balance correction, usually at pre-set points, along a shaft. Potential benefits of this methodology are initially determined by analysis of a high-speed, simply supported, plain flexible shaft, with uniform eccentricity which shows that near elimination of the 1st lateral critical speed, (LCS) is possible, thereby allowing safe operation with much reduced LCS margins. Further study of concentrated, residual imbalances provides several new insights into the behaviour of the balancing sleeve concept: 1) a series of concentrated imbalances can be regarded simply as an equivalent level of uniform eccentricity, and balance sleeve compensation is equally applicable to a generalised unbalanced distribution consisting of any number of ii concentrated imbalances, 2) compensation depends on the sum of the applied balancing sleeve moments and can therefore be achieved using a single balancing sleeve (thereby simulating a single encastre shaft), 3) compensation of the 2nd critical speed, and to a lesser extent higher orders, is possible by use of two balancing sleeves, positioned at shaft ends, 4) the concept facilitates on-site commissioning of trim balance which requires a means of adjustment at only one end of the shaft, thereby reducing commissioning time, 5) the Reaction Ratio, RR (simply supported/ encastre) is independent of residual eccentricity, so that the implied benefits resulting from the ratio (possible reductions in the equivalent level of eccentricity) are additional to any balancing procedures undertaken prior to encastre simulation. The analysis shows that equivalent reductions of the order of 1/25th are possible. Experimental measurements from a scaled model of a typical drive coupling employed on an industrial gas turbine package, loaded asymmetrically with a concentrated point of imbalance, support this analysis and confirms the operating mechanism of balancing sleeve compensation and also it’s potential to vastly reduce shaft deflections/ reaction loads.

No description available.

<p> Solar radiation pressure alters satellites' eccentricity by accelerating and decelerating them during each orbit. The accumulated perturbation cancels yearly for geostationary satellites, but meanwhile the perigee radius changes. Disposed satellites must be reorbited higher to compensate, using more fuel. The examined disposal orbit points toward the Sun and uses the satellite's natural eccentricity. This causes the eccentricity vector to only change direction, keeping the perigee radius constant. This thesis verifies this behavior over one year with an analytical derivation and MATLAB simulation, gaining useful insights into its cause. The traditional and proposed disposal orbits are then modeled using NASA's GMAT for more realistic simulations. The proposed orbit's sensitivity to satellite and initialization errors is also examined. Relationships are developed to show these errors' effect on the perigee radius. In conclusion, while this orbit can be used in the short term, margins are necessary to guarantee protection of the geostationary belt.</p>

<p> Standard maneuvering tests were executed at the IIHR wave basin using free-running model. Experiments in calm water as well as wave were performed for a surface combatant with primary focus on establishing a validation benchmark dataset for an unsteady Reynolds-averaged Navier-Stokes (RANS)-based computational fluid dynamics (CFD) code used for computing both air and water flow around a ship. Experimental data from this study will also be used in developing a mathematical model for computing the external forces exerted on the ship model during maneuvering. The geometry is 1/49 scale fully appended ONR Tumblehome model 5613, with a length of 3.147 m. Tests are performed in 20 x 40 x 4.5 m wave basin which is equipped with six plunger-type wave makers, free-running system, as well as carriage tracking system. The maneuvering tests included course keeping, zigzag, and turning tests in head and following waves as well as calm water. Course keeping and zigzag tests were performed at Froude number 0.2 while turning tests were performed at Froude numbers 0.1, 0.2, and 0.3. While the wave height to wavelength ratio was held constant at 0.02 for all the test cases, experiments were performed at three different wavelengths for each Froude number case at different wave encounter angles. Maneuvering trajectories for each test as well as results such as roll, pitch, yaw and yaw rate results were analyzed for all tests. Drift angle, drifting distance, tactical diameter, advance and transfer results from turning tests were obtained and tactical diameter and advance are compared to other facilities data. 1^st and 2^nd overshoot angles results from zigzag tests and counter rudder angle and speed loss in course keeping were obtained and documented along with the turning test results to help in developing a mathematical model for calculating the forces and moments acting on the ship model and to establish a benchmark data for the CFD validation use.</p>

<p> An ever-present challenge at most active mining operations is controlling blast-induced damage beyond design limits. Implementing more effective wall control during blasting activities requires (1) understanding the damage mechanisms involved and (2) reasonably predicting the extent of blast-induced damage. While a common consensus on blast damage mechanisms in rock exists within the scientific community, there is much work to be done in the area of predicting overbreak. A new method was developed for observing near-field fracturing with a borescope. A field test was conducted in which a confined explosive charge was detonated in a body of competent rhyolite rock. Three instrumented monitoring holes filled with quick-setting cement were positioned in close proximity to the blasthole. Vibration transducers were secured downhole and on the surface to measure near-field vibrations. Clear acrylic tubing was positioned downhole and a borescope was lowered through it to view fractures in the grout. Thin, two-conductor, twisted wires were placed downhole and analyzed using a time-domain reflectometer (TDR) to assess rock displacement. Fracturing in the grout was easily observed with the borescope up to 3.78 m (12.4 ft) from the blasthole, with moderate fracturing visible up to 2.10 m (6.9 ft). Measured peak particle velocities (PPV) at these distances were 310 mm/s (12.2 in./s) and 1,490 mm/s (58.5 in./s), respectively, although no fracturing was observed near the depth of the vibration transducers located 3.78 m (12.4 ft) from the blasthole. TDR readings were difficult to interpret but indicated rock displacement in two of the monitoring holes. Three methods were used to predict the radial extent of tensile damage around the blasthole: a modified Holmberg&ndash;Persson (HP) model, a shockwave transfer (SWT) model, and a dynamic finite element simulation using ANSYS Autodyn^TM. The extent of damage predicted by the HP and SWT models is similar to field measurements when using static material properties of the rock, but is underestimated using dynamic material properties. The Autodyn^TM model significantly overpredicted the region of damage but realistically simulated the zones of crushing and radial cracking. Calibration of material parameters for the Autodyn^TM model would be needed to yield more accurate results.</p>

<p> Rainfall estimation from satellite observations has uncertainties and inconsistency at different locations and so four different satellite products were selected for validation in Saudi Arabia. The satellite products selected for this study are TRMM, PERSIANN, CMORPH, and GSMap-MVK which are compared with gauge observed rainfall data using conventional statistical methods at daily, 10-daily, and monthly time scale. The validation results show that all the products can predict rainfall in the study area reasonably well but overestimates rainfall in the regions. However, this bias is comparatively less in the semi-arid part of the country where most of the rain falls. Therefore, all the four satellite products were used in SWAT model to study the hydrologic response in a semi-arid watershed located in the western part of the country. Results show that simulation from TRMM rainfall estimates agrees better with that of gauge observations at daily time scale.</p>