An attempt was made to calibrate a steady state activated sludge model (ASM2d) for the biological nutrient removal process at the Gold bar wastewater treatment plant. This calibrated model could be used on a regular basis to test various operational strategies and predict effluent quality under different scenario. To achieve this historic data from the plant database was collected based on 24 composite samples. A trial and error method of wastewater characterization of the primary effluent was attempted using the influent advisor module of the GPS-[X] software. Sensitivity analysis of kinetic parameters was carried out and the most important ones identified were calibrated (default values were modified) based on literature. After calibration it was observed that the model was overestimating the concentrations of carbonaceous biological oxygen demand, total suspended solids and orthophosphate in the effluent, compared to the actual value measured at the plant. Similarly the effluent ammonia concentration was underestimated for most days along with the nitrate and nitrite concentration. This clearly indicated the need for a more accurate calibration based on experimental data to improve prediction capabilities and the reliability of the model. / Environmental Science

Incremental sheet forming process is a relatively new method of forming which is increasingly being used in the industry. Complex shapes can be manufactured using this method and the forming operation doesn't require any dies. High strains of over 300 % can also be achieved. Incremental sheet forming method is used to manufacture many different components presently. Prototype examples include car headlights, tubs, train body panels and medical products. The work done in the thesis deals with the prediction of the steady state forces acting on the tool during forming. Prediction of forces generated would help to design the machine against excessive vibrations. It would help the user to protect the tool and the material blank from failure. An efficient design ensures that the tool would not get deflected out of its path while forming, improving the accuracy of the finished part. To study the forces, experiments were conducted by forming pyramid and cone shapes. An experimental arrangement was set up and experimental data was collected using a data acquisition system. The effect that the various process parameters, like the thickness of the sheet, wall angle of the part and tool diameter had on the steady state force were studied. A three dimensional model was developed using commercial finite element software ABAQUS using a new modeling technique to simulate the deformation of the sheet metal blank during incremental sheet forming. The steady state forces generated for any shape, with any set of parameters used, could be predicted using the numerical model. The advantage of having a numerical model is that the forces can be predicted without doing experiments. The model was used to predict the steady state forces developed during forming of pyramid and cone shapes. The results were compared and were seen to be reasonably close to the experimental results. Later, the numerical model was validated by forming arbitrary shapes and comparing the value obtained from simulations to the value of the measured steady state forces. The results obtained from the numerical model were seen to match very well with the experimental forces for the new shapes. The numerical model developed using the new technique was seen to predict forces to a reasonable extent with less computational time as compared to the models currently available.

Research Doctorate - Doctor of Philosophy (PhD) / Slug flow dense phase pneumatic conveying can be a most reliable, efficient method for handling a remarkably wide range of dry bulk solids. Models for pressure drop over slugs in the low-velocity slug-flow pneumatic conveying by many researchers only took the force balance into account with the pressure drop. However, the nature of the slug flow pneumatic conveying is discontinuous and seldom becomes steady during the conveying period which requires further investigation. The fundamental understanding to gas/slug interaction in this thesis is that, by being a dynamic system, the faster a slug moves at a speed, the larger the space is left behind the slug. The gas feeding into the conveying system has to fill the increased space first then permeates through the slug and provides a push force on the slug. With gas permeation rate defined by the permeability factor, the derivative of the upstream pressure based on the air mass conservation law has been developed. For a given conveying system, the pressure in the pneumatic conveying system can be solved for steady conditions or numerically simulated for unsteady conditions. Parametric analysis have been conducted for pressure drop factors and found that slug velocity is the major reason causing the pressure fluctuation in the pneumatic conveying system. To verify the pressure drop model, this model has been applied to single slug cases and compared with experimental results for five different bulk materials, showing good results. Three distinct zones, i.e. Fixed Bed Zone, Initial Slug Zone and Reliable Slug Zone, have been found to exist in the relationship between slip velocity and pressure gradient. Lastly this model has also been applied to a multiple slug system under uniform conditions. In all, the fundamental gas pressure/pressure drop model developed in this thesis approaches slug flow conveying from a different viewpoint from the traditional momentum and material stress models developed by previous researchers, and provides a way of assessing the non-steady flow behaviour in granular dense phase pneumatic conveying. This model not only attains a better understanding of slug flow behaviour but also increases the accuracy of predicting the parameters.

Research Doctorate - Doctor of Philosophy (PhD) / Slug flow dense phase pneumatic conveying can be a most reliable, efficient method for handling a remarkably wide range of dry bulk solids. Models for pressure drop over slugs in the low-velocity slug-flow pneumatic conveying by many researchers only took the force balance into account with the pressure drop. However, the nature of the slug flow pneumatic conveying is discontinuous and seldom becomes steady during the conveying period which requires further investigation. The fundamental understanding to gas/slug interaction in this thesis is that, by being a dynamic system, the faster a slug moves at a speed, the larger the space is left behind the slug. The gas feeding into the conveying system has to fill the increased space first then permeates through the slug and provides a push force on the slug. With gas permeation rate defined by the permeability factor, the derivative of the upstream pressure based on the air mass conservation law has been developed. For a given conveying system, the pressure in the pneumatic conveying system can be solved for steady conditions or numerically simulated for unsteady conditions. Parametric analysis have been conducted for pressure drop factors and found that slug velocity is the major reason causing the pressure fluctuation in the pneumatic conveying system. To verify the pressure drop model, this model has been applied to single slug cases and compared with experimental results for five different bulk materials, showing good results. Three distinct zones, i.e. Fixed Bed Zone, Initial Slug Zone and Reliable Slug Zone, have been found to exist in the relationship between slip velocity and pressure gradient. Lastly this model has also been applied to a multiple slug system under uniform conditions. In all, the fundamental gas pressure/pressure drop model developed in this thesis approaches slug flow conveying from a different viewpoint from the traditional momentum and material stress models developed by previous researchers, and provides a way of assessing the non-steady flow behaviour in granular dense phase pneumatic conveying. This model not only attains a better understanding of slug flow behaviour but also increases the accuracy of predicting the parameters.

This thesis describes a new approach to accelerate the simulation of the steady-state response of nonlinear circuits using the Harmonic Balance (HB) technique. The approach presented in this work focuses on direct factorization of the sparse Jacobian matrix of the HB nonlinear equations using a Graphics Processing Unit (GPU) platform. This approach exploits the heterogeneous structure of the Jacobian matrix. The computational core of the proposed approach is based on developing a block-wise version of the KLU factorization algorithm, where scalar arithmetic operations are replaced by block-aware matrix operations. For a large number of harmonics, or excitation tones, or both the Block-KLU (BKLU) approach effectively raises the ratio of floating-point operations to other operations and, therefore, becomes an ideal vehicle for implementation on a GPU-based platform. Motivated by this fact, a GPU-based Hybrid Block KLU framework is developed to implement the BKLU. The proposed approach in this thesis is named Hybrid-BKLU. The Hybrid-BKLU is implemented in two parts, on the host CPU and on the graphic card’s GPU, using the OpenCL heterogeneous parallel programming language. To show the efficiency of the Hybrid-BKLU approach, its performance is compared with BKLU approach performing HB analysis on several test circuits. The Hybrid-BKLU approach yields speedup by up to 89 times over conventional BKLU on CPU.

Small-amplitude, high-frequency (ultrasound) forcing of fluid/particle systems is being used in a number of applications associated with non-destructive fluid mixing and the movement/manipulation of particles in suspension. Of most importance in this context are the second-order, steady, effects arising from the nonlinear interaction of a leading-order oscillatory field with itself. In this thesis we consider some of these steady effects in both incompressible and compressible fluids. We first consider the axisymmetric steady streaming generated in an incompressible, viscous fluid contained between two (radially) infinite parallel plates, each oscillating in a direction normal to its own plane. In the limit of small-amplitude, high-frequency oscillations, we show that the steady-streaming flow in the fluid bulk is driven by thin streaming sublayers at the plates, at which the normal velocity is zero and the radial velocity varies linearly with distance from the axis of rotational symmetry. Effectively, in the bulk flow, the bounding plates appear as (no-slip) impermeable walls that stretch radially. This bulk-flow problem is extended to allow for the analogous steady flow of two immiscible, incompressible, viscous fluids, each undergoing a radial-stretching motion appropriate to high-frequency steady streaming. For a flat interface between the fluids, a self-similar solution reduces the Navier--Stokes equations to a nonlinear boundary-value problem, the solution of which exhibits an interesting structure in the limit of large Reynolds number. In this limit, solutions can be found using matched asymptotic expansions, but the location of the interface between the fluids can only be determined if terms that are exponentially small in the Reynolds number are included. It is shown that for fluids of almost-equal densities, exponentially-small differences can have a leading-order effect on the observed flow. The second part of the thesis is concerned with the (steady) acoustic radiation force on a rigid sphere submerged in a compressible, inviscid fluid, when the wavelength of the incident acoustic field is large compared to the radius of the sphere. In this limit, a matched asymptotic expansion method is used to derive an expression for the acoustic radiation force, on both fixed and free rigid spheres, due to a range of incident fields. For incident acoustic fields that are appropriate to planar and circular waveguides/channels, expressions are derived for the scattered field and the radiation force on a rigid sphere in the long-wavelength limit. Fixed and free spheres located both on and off the axis of symmetry of these incident fields are considered. This is an extension to the current literature, in which numerical methods are used to examine the scattering from spheres in an off-axis position, and problems are restricted to the consideration of fixed spheres only. It is shown that there are stable and unstable positions within the waveguide where any off-axis acoustic radiation force vanishes, leaving only an along-channel component. For free spheres, these positions are shown to be dependent on the relative particle density and it is suggested that this may allow for a mechanism to sort such small particles radially in a circular waveguide, if secondary scattering effects are neglected.

With the projected growth of wind energy in the United States expected to account for 20% of the energy portfolio by 2030, it can be expected that wind turbines will not only increase in number, but also in size. This increase in size implies that internal components, such as the gearbox, will also increase to handle the higher loads. And given the high failure rates for gearbox components already in existence, one could expect more failure if nothing is done to improve reliability. It is well known that wind loading is not constant, rather it is random and ultimately causes fatigue loading. This thesis is concerned with studying what the effects of dynamic loading are on a smaller gear system. It is assumed the findings of this study can be scaled to a larger wind turbine system. A simple spur gear pair is first simulated at constant loading to establish a baseline and then run with a sinusoidal input with differing amplitudes and frequencies. The hypothesis is that by varying the amplitude and frequency, the responses for gear contact force and input and output shaft torques will also vary. And if these variations are noted, then conclusions may be drawn as how the frequency and amplitude influence the system. After which, it may then be correlated to a wind turbine system. Knowing what affects the frequency and amplitude have on a smaller system may help to establish guidelines. For this model, mechanical simulation software is used to build a multibody dynamics model of a spur gear system with flexible shafts. Using known wind data obtained near Amarillo, TX, a matrix of possible frequencies and amplitudes for a sinusoidal input are implemented and the solutions compared to those at constant loading. It was found that the system responded similarly regardless of input, showing RMS values for accelerations of approximately 50 m/s2, gear contact forces of 520 N, input shaft torques of 42 Nm, and output shaft torques of 78 Nm. This behavior is not expected is most likely due to insufficiencies in the assumptions made to construct the model.

Critical components in coal-fired power plants such as final superheater heat exchangers experience severe conditions associated with high metal temperatures and high temperature gradients during base load and transient operations. Such adverse conditions could significantly reduce the life span of the components, especially due to the requirement of greater plant flexibility that is an essential part of the global power system transformation. Integrated thermofluid process models can be employed to obtain a better understanding of the relationship between the operational conditions and the metal temperatures. Thus, a methodology was developed to model radiant superheater heat exchangers in steady state and transient operations. The methodology is based on a network approach which entails solving the transient one-dimensional forms of the conservation equations for mass, energy and momentum. The model building blocks account for the convective thermal resistance on the steam side, the conductive thermal resistances of the tube wall and scaling or fouling on the tube walls, as well as the convective and radiative thermal resistances and direct radiation on the flue gas side. The model captures the physical layout of the tube passes in a tubesheet via the arrangement of the network building blocks. It is also possible to connect tubesheets together across the width of the boiler as per the arrangement in a real plant. The modelling methodology was first used to develop a process model of a convective cross-flow primary superheater heat exchanger with complex flow arrangement. The dual-tube 12-pass superheater was discretized along the flue gas flow path as well as along the steam flow path. The model was qualitatively validated using real plant data from literature and for reference purposes also systematically compared to conventional lumped parameter models. The ability of the model to analyse the effect of ramp rate during load changes on the tube metal temperature was demonstrated, as well as the ability to determine the maldistribution of flow and temperature on the steam and flue gas sides. The methodology was also applied to model a U-shaped radiant superheater heat exchanger. Due to the challenges associated with obtaining comprehensive real plant data in an industrial setting, a validation methodology was proposed that is based on a combination of plant design C-schedules and a boiler mass and energy balance, as well as limited plant measurements. The consistent comparisons with C-schedule data provide evidence of the validity of the model, which was further demonstrated via the comparisons with real plant data. The model allows prediction of the steam mass flow and temperature distribution going into the outlet stub headers as well as the main outlet headers for different inlet flow and temperature distributions on the steam and flue gas sides. These results were compared to detail real-plant measurements of the outlet header temperatures. The model also allows prediction of the metal temperatures along the length of the tubes which cannot readily be measured in the plant. The model was applied to demonstrate the impact of different operational conditions on the tube metal temperatures. Such integrated process models can be employed to study complex thermofluid process phenomena that may occur during intermittent, transient and low load operation of power plants. In addition, such models could be useful for predictive and preventative maintenance as well as online condition monitoring.

BACKGROUND: Previous research has shown that the ventilatory threshold (VT) correlates highly with onset of lactate accumulation and maximal steady-state exercise (MSS) level. Also, studies have shown the VT is useful in prescribing exercise for cardiac patients in that it gives an exercise intensity at which the patient is metabolically stable. METHODS: The purpose of this study was to determine if a MSS response could be achieved at an exercise intensity corresponding to the VT for patients with CAD. A group of 31 patients with CAD performed a maximal effort treadmill exercise test in which respiratory gas exchange was measured. The VT was determined using the V-slope method of computer regression analysis of the plot of carbon dioxide production versus oxygen consumption. Subjects then performed a constant load treadmill test a speed and grade that corresponded to the VT. Heart rate (HR), systolic blood pressure (SBP), and rating of perceived exertion (RPE) evaluated for steady-state responses. If subjects showed a steady-state response in two of these three parameters they were scored as having achieved a maximal steady-state (MSS+) response; those not meeting this standard were scored as failing to achieve maximal steady-state (MSS-) response. Subjects were analyzed as an entire group (N=31), as well as analyzed in subsets according to history of myocardial infarction (MI+, N=20; MI-, N=11) and administration of beta-blocker medications (BB+, N=16; BB-, N=15). RESULTS: Overall, subjects demonstrated significantly more MSS+ responses than MSS- responses (80% Vs 20%, P<0.05). Analysis of the subgroup data showed that it was the patient s with a history of MI (MI+ =85%, P<0.05) and those not receiving beta-blocker medications (BB- = 93%, P<0.05) who had significantly greater proportions of subject achieving MSS+ responses in the fixed load exercise condition. Conversely patient in the MI- (73 %, P < 0.05) and BB (69% P < 0.05) groups showed no significant differences in the number of MSS+ and MSS- responses. CONCLUSIONS: The VT, as measured during ramp exercise testing on the treadmill, provided a basis for establishing a maximal steady-state load in terms of cardiovascular and perceptual variables for 80% of the patients in the CAD study group. The measurements of HR, SBP, and RPE are easily obtained in a clinical setting and thus enable the VT to be used in bringing about a more efficacious exercise prescription. The validity of this method may be questioned, however, for patient with out a history of MI and for those receiving beta-blocker medications. / Master of Science

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