Several industries use what is called rotating workforce scheduling. This often means that employees are needed around the clock seven days a week, and that they have a schedule which repeats itself after some weeks. This thesis gives an introduction to this kind of scheduling and presents a review of previous work done in the field. Two different optimization models for rotating workforce scheduling are formulated and compared, and some examples are created to demonstrate how the addition of soft constraints to the models affects the scheduling outcome. Two large realistic cases, with constraints commonly used in many industries, are then presented. The schedules are in these cases analyzed in depth and evaluated. One of the models excelled as it provides good results within a short time limit and it appears to be a worthy candidate for rotating workforce scheduling.

The initial rotation of flat, rectangular plates in quiescent flow were studied experimentally using two-dimensional and stereoscopic particle image velocimetry. The study examined the vortex dynamics of spanwise vorticity created on the upper, leeward surface of each plate of aspect ratio 2 and 4, which consists primarily of a leading-edge vortex. Reynolds numbers of 4,000, 8,000, and 16,000 based on the tip velocity and angles of attack of 25°, 35°, and 45° were investigated at five different azimuthal locations (90°, 180°, 235°, 270°, and 320°). The 25% and 50% spanwise positions for the aspect ratio 4 plate and 50% spanwise position for the aspect ratio 2 plate were studied. For the 25% and 50% spanwise location for the aspect ratio 4 and 2 plate, respectively, the leading-edge vortex structure's shape and coherence appear to be evolving temporally as the plate begins its initial motion. Leading-edge vortex circulation measurements confirm there is a non-monotonic trend showing increasing values until an azimuthal position of approximately 220° where there is a dip in the circulation values, but the circulation then rises towards the end of the range of azimuthal positions investigated. A strong region of counter-rotating vorticity was observed on the surface of the plate beneath the leading-edge vortex from the interaction of the leading-edge vortex with the plate. It was hypothesized that the interactions between the leading-edge vortex and counter-rotating vorticity are an important factor in governing the dynamics and strength of the leading-edge vortex which may ultimately determine whether the leading-edge vortex remains attached. To validate this claim, a transport analysis of the vorticity in the leading-edge vortex was developed to determine the contributions of spanwise flux, tilting of in-plane vorticity components, the shear layer, and annihilation has on the rate of change of circulation of the leading-edge vortex in the spanwise direction. Results of this analysis indicate that annihilation of the leading-edge vortex from entrainment of the counter-rotating vorticity is an important factor in governing the dynamics of the leading-edge vortex.

Overend et al [68] designed a viscometer to measure the viscosity of slurries that have a tendency to settle. This viscometer consists of a rotating ribbed rotor surrounded by a stationary slotted sleeve; this system is then placed eccentrically within an inclined rotating bowl. It, is claimed that this overcomes most of the difficulties encountered when attempting to obtain accurate measurements for these types of mixtures. If the mixture being sheared within the annulus does not represent the true composition of the slurry being, tested then the results are expected to be inaccurate. The presence of sediment at the bottom of the rotor or the formation of large masses of particles within the flow domain will affect the accuracy of the measurements obtained. This dissertation studies the amount of flow through the slotted sleeve and the region, or regions, of low shear rate within the flow domain. Assuming that end-effects are unimportant and that the slurries can be replaced by a single-phase fluid, three two-dimensional models are proposed. These models are designed to capture the large-slot construction of the sleeve and the, approximate, non-Newtonian behaviour of the slurries. The first two models solve analytically (using a regular perturbation scheme) and numerically (using a finite volume method) the moderate-and large-Reynolds-number flow, and the third model uses a finite volume method to study the flow patterns developed by pseudoplastic fluids. The results show that the mixing of the slurry is expected to be enhanced by moving the concentric system (i.e., the rotor and the slotted sleeve) close to the rotating bowl and using low to moderate speeds for the rotor and bowl. In addition, when the cylinders rotate in the same directions, two (counter-rotating) eddies are present within the flow domain; whereas, only one eddy (rotating counter-clockwise) is ++ / present when the cylinders rotate in opposite directions. The presence of eddies in the former situation inhibits the flow through the sleeve; while, for moderate rotorspeeds, the flow through the sleeve is enhanced in the latter. When the slurry assumed pseudoplastic, we observe a region of low shear rate located near the dividing streamline present within the flow field. The distribution of shear rate within the flow field is shown to be affected by factors such as the rate of diffusion of the apparent viscosity and the value of the power law index. Therefore, this study suggests that for certain types of slurries, concentrations of particles exist within the domain and that the mixing of slurries can be impeded by the presence of eddies within the main flow field.

Static Whirling Rods: Past researchers suggested that “static instabilities” exist at certain rotational speeds of whirling rods. This thesis shows these instabilities are an artefact of the material constitutive laws that are being used well outside their range of applicability. An alternative approach is developed where strains due to rotation are separated from the superimposed vibration. This enables the generally predicted lowering of longitudinal natural frequencies with rotational speed shown to be simply a result of the bulk changes in the geometry of whirling rods. Steady state equations of whirling rods are formulated in Lagrangian coordinates. Due to the non-linear nature of the governing equations, an original numerical method is applied to solve the problem. Numerical results are compared with analytical results obtained from the linearized uniaxial model. There is a close agreement between these two models at low angular velocities. However, at high angular velocities, discrepancies between them arise, confirming that the nonlinear strain-displacement relationship has significant effect on the results and the inferred “static instabilities”. This approach first solves the “static” problem of the deformed geometry of a highly strained whirling rod before longitudinal natural modes are determined by classical methods. Furthermore, conditions for existence and uniqueness of solutions are derived. Dynamic Rotating Annuli: In-plane modes of vibration of annular plates are investigated. Two different models of equations one from Bhuta and Jones and the other from Biezeno and Grammel that govern the rotational motions of annuli will be studied. Since Biezeno and Grammel’s model was originally derived in Eulrian coordinates, their model will be transformed to the Lagrangian coordinates for the purpose of comparison with Bhuta and Jones’ model. / The solutions of the equations assume small oscillations of vibration being superimposed on the steady state of the annulus while it is in rotation. Exact and approximate solutions are obtained for the Bhuta and Jones’ model, where the approximate solutions on in-plane displacements and natural frequencies are acquired by ignoring the Coriolis effect. A proposed numerical scheme is implemented to solve the governing equations coupled with radial and circumferential displacements. Uniqueness of solutions will be mentioned although it will not be rigorously derived because it is out of the scope of this thesis. Approximate analytical results show that both radial and circumferential natural frequencies are decreasing when the rotational speed of an annulus is increasing. The exact and numerical results on both models that take the Coriolis effect into account show that radial natural frequencies are increasing and circumferential natural frequencies are decreasing when the rotational speed of an annulus is increasing.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 86-97.

This thesis presents a study of a novel suspension system which is placed inside a vehicle's wheel. The In-wheel suspension system isolates the sprung mass from excitations similar to conventional suspension systems. In traditional suspension systems the isolation is provided by spacious and complicated mechanisms, and mainly in the vertical direction. However, the in-wheel suspension system, not only fits the suspension mechanism inside the unused space between a wheel’s rim and hub, but also allows for isolation both in vertical and horizontal directions. The main focus of this thesis is to study, investigate, and show the feasibility of applying such suspension system to a vehicle. This research is conducted on low speed, low load, and non-powered vehicles such as hand trucks and baby strollers. This helps to escape from the complications of a complex system like a road vehicle. It also demonstrates the versatility of the in-wheel suspension idea. The objective of the project is to scrutinize a simple but practical in-wheel suspension system and demonstrate its applicability. The research begins with the dynamics modeling of an in-wheel suspension system. This suspension has been previously developed at the University of Waterloo for a wheelchair. The dynamics model evaluates the response of the suspension system and investigates the influence of various design parameters on the in-wheel suspension. The study is then continued to improve the design by replacing its rigid mechanism links with optimized compliant structures. This reduces the system's complexity and weight while boosting its performance. Furthermore, a general optimization code is developed to design and optimize flexible members for in-wheel suspension systems. The optimization program is then used to design and optimize two prototypes for hand trucks. Finally, the in-wheel suspension system for a hand truck is tested and evaluated. The experimental results also verify the simulation results and verify the developed optimization design program.

This thesis presents a study of a novel suspension system which is placed inside a vehicle's wheel. The In-wheel suspension system isolates the sprung mass from excitations similar to conventional suspension systems. In traditional suspension systems the isolation is provided by spacious and complicated mechanisms, and mainly in the vertical direction. However, the in-wheel suspension system, not only fits the suspension mechanism inside the unused space between a wheel’s rim and hub, but also allows for isolation both in vertical and horizontal directions. The main focus of this thesis is to study, investigate, and show the feasibility of applying such suspension system to a vehicle. This research is conducted on low speed, low load, and non-powered vehicles such as hand trucks and baby strollers. This helps to escape from the complications of a complex system like a road vehicle. It also demonstrates the versatility of the in-wheel suspension idea. The objective of the project is to scrutinize a simple but practical in-wheel suspension system and demonstrate its applicability. The research begins with the dynamics modeling of an in-wheel suspension system. This suspension has been previously developed at the University of Waterloo for a wheelchair. The dynamics model evaluates the response of the suspension system and investigates the influence of various design parameters on the in-wheel suspension. The study is then continued to improve the design by replacing its rigid mechanism links with optimized compliant structures. This reduces the system's complexity and weight while boosting its performance. Furthermore, a general optimization code is developed to design and optimize flexible members for in-wheel suspension systems. The optimization program is then used to design and optimize two prototypes for hand trucks. Finally, the in-wheel suspension system for a hand truck is tested and evaluated. The experimental results also verify the simulation results and verify the developed optimization design program.

Concentric rotating cylinder and turbulent mixing devices have been frequently used in studying mixing and particle coagulation. However, these apparatus develop simple laminar flow (concentric rotating cylinders) or do not have well-defined flow (turbulent mixing devices). In this work, the eccentric rotating cylinder apparatus was investigated to find applicability for the improved study of coagulation based on the modified analytical solution of Ballal and Rivlin. Various eccentricity ratios, rotation speeds and viscosities were simulated to obtain optimum operating conditions. Inertial forces working on the fluid increased as the eccentricity ratio and rotation speed increase. As inertial forces increase, the eddy developed in wide clearance was more skewed in the direction of rotation. Both root-mean-square velocity gradient and average principal strain-rate, were increased by increasing eccentricity ratio. avaerage principal strain-rate were linearly increased as rotation speed increases, which suggested that average prinipal strain-rate can properly represent mixing intensity. Comparison of average principal strain-rate and RMS velocity gradient revealed that RMS velocity gradient overestimated mixing intensity and its error increased as eccentricity ratio increases. This study showed that the eccentric rotating cylinder apparatus has a non-uniform velocity distribution with well-defined fluid dynamics. Therefore, the eccentric rotating cylinder apparatus can be applicable as a model flocculator. However, in order to achieve reliable model predictability, the fluid Reynolds number must be below 200.

Fouling, a problem since the first heat exchanger was created, has been the focus of various studies since the 1970s. In particular, crude oil fouling is a costly and problematic type of heat exchanger fouling that occurs in the preheat train to the atmospheric distillation column in petroleum refineries. Previous experiments have been designed to determine the causes of fouling using less than one gallon of crude oil and accumulating test results within a day. These experiments will be the basis of the Rotating Fouling Unit (RFU) at Heat Transfer Research Inc. (HTRI). The RFU focuses on better controlling the shear stress and heat transfer distribution along the surface of the heated test section by analyzing Taylor-Couette flow experiments and using them as a basis to better predict the flow across the heated surface of the test section in the RFU. Additionally, the equations for Taylor-Couette flow are used to verify the 2D flow simulations of the RFU to ensure the accuracy of the results. The design of the RFU incorporates data acquisition with a variety of measurements that will facilitate automatic and accurate data collection, so the results can be easily compared to previous fouling experiments. The RFU will act as a supplement to the High Temperature Fouling Unit (HTFU) at HTRI, and provide data comparable to that of the HTFU in order to better understand crude oil fouling. Computer simulations can accurately predict the shear stress and heat transfer coefficient along the surface of the test probe and help verify the improvements made to the original batch stirred cell designs.

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