<p> The management of Sclerotinia stem rot of soybean caused by [Sclerotinia sclerotiorum (Lib) de Bary] integrates several tactics that may include biological control. However, the successful incorporation of biocontrol agents into the management program might be hindered by agrochemical application. To determine the compatibility of potential biocontrol agents with agrochemicals, growth of Trichoderma asperellum, T. gamsii and Coniothyrium minitans was tested with selected chemicals on agar plates. Effects of selected agrochemicals on C. minitans growth and biocontrol activity were also tested in soil and in water. On amended agar media, Trichoderma spp. and C. minitans were insensitive to the herbicide lactofen and were inhibited to varying degrees by some of the tested fungicides. The survival and the biocontrol activity of C. minitans in the soil was not impaired by propamocarb HCl, tetraconazole or lactofen treatments. When mixed in a water suspension, none of the selected the herbicides or a biofertilizer affected C. minitans population in the suspension over a 4 h period, suggesting that they can be applied in a tank mix. Under field conditions, Trichoderma spp. and C. minitans reduced the disease severity and viable sclerotial population of S. sclerotiorum, but their efficacy varied across years and location. Co-application with lactofen enhanced the efficacy of disease suppression and yield in some cases but reduced the efficacy in others. The effect of the biological control agents or chemicals evaluated on yield during three years of trials was inconsistent.</p>

<p> Proper orthogonal decomposition-based reduced order modeling is a technique that can be used to develop low dimensional models of fluid flow. In this technique, the Navier-Stokes equations are projected onto a finite number of POD basis functions resulting in a system of ODEs that model the system. The overarching goal of this work is to determine the best methods of applying this technique to generate reliable models of fluid flow. The first chapter investigates some basic characteristics of the proper orthogonal decomposition using the Burgers equation as a surrogate model problem. In applying the POD to this problem, we found that the eigenvalue spectrum is affected by machine precision and this leads to non-phsical negative eigenvalues in the POD. To avoid this, we introduced a new method called deflation that gives positive eigenvalues, but has the disadvantage that the orthogonality of the POD modes is more affected by numerical precision errors. To reduce the size of eigenproblem of POD process, the well-known snapshot method was tested. It was found that the number of snapshots required to obtain an accurate eigenvalue spectrum was determined by the smallest time scale of the phenomenon. After resolving this time scale, the errors in the eigenvalues and modes drop rapidly then converge with second-order accuracy. After obtaing POD modes, the ROM error was assessed using two errors, the error of projection of the problem onto the POD modes (the out-plane error) and the error of the ROM in the space spanned by POD modes (the in-plane error). The numerical results showed not only is the in-plane error bounded by the out-plane error (in agreement with theory) but it actually converges faster than the out-of-plane error. The second chapter is dedicated to building a robust POD-ROM for long term simulation of Navier-Stokes equation. The ability of the POD method to decompose the simulation and the capability of POD-ROM to simulate a low and high Reynolds flow over a NACA0015 airfoil was studied. We observed that POD can be applied for low Reynolds flows successfully if a proper stabilization method is used. For the high Reynolds case, the convergence of the eigenvalues spectrum with respect to duration of time window from we observed that the number of modes needed to simulate a certain time window increases almost linearly with the length of the time window. So, generating a POD-ROM for high Reynolds flow that reproduced the correct long-term limit cycle behavior needs many more modes than has been usually used in the literature. In the last chapter, we address the problem that the standard method of generating POD modes may be inaccurate when used "off-design" (at parameter values not used to generate the POD). We tested some of the popular methods developed to remedy that problem. The accuracy of these methods was in direct relation with the amount of data provided for those methods. So, in order to generate appropriate POD modes, very large POD problems must be solved. To avoid this, a new multi-level method, called recursive POD, for enriching the POD modes is introduced that mathematically provides optimal POD modes while reducing the computational size of problem to a manageable degrees. A low Reynolds flow over NACA 0015, actuated with constant suction/blowing of a fluidic jet located on top surface of airfoil is used as benchmark to test the technique. The flow is shifted from one periodic state to another periodic state due to fluidic jet effect. It was found that the modes extracted with the recursive POD method are as accurate as the modes of the best known method, global POD, while the computational effort is lower. </p>

<p>Numerical investigations of a jet in crossflow with two different coil inserts at four ratios of jet to the crossflow mean velocities were performed. The coils had a length to diameter (L/D) ratios of 2 and 11.25 and the velocity ratios, r, were 0.5, 1.0, 2.0, and 5.0. Results show when r=0.5, with coil inserts, jet penetration into the crossflow is reduced with increased entrainment near the jet outlet. Further results show that when r=2, and 5, near the jet outlet entrainments are reduced, with jet penetrating into higher elevations, before tilting in the direction of the crossflow. Comparing the results for the two coil inserts, with the shorter coil insert, higher penetration is obtained and with the longer coil, turbulent kinetic energy is increased in the near field. </p>

<p> Recently, diesel engine cycle simulation has been acknowledged as an effective way for the development and performance optimization of compression ignition engines operating on a variety of fuels. The goal of this research was, therefore, to develop a JP-8 surrogate with a limited number of fuel components so that its chemical mechanism could be developed for its use with computational fluid dynamics (CFD) codes for enabling time-efficient diesel engine cycle simulation. In order to achieve this goal, a new approach was developed for the formulation of surrogate for compression ignition engine application. The development approach required the surrogate to match several properties of the target JP-8 fuel. </p><p> A total of six different surrogates, with maximum number of components limited to four, was developed using a MATLAB code, Ignition Quality Tester (IQT), and HYSYS simulation software. Then, all the surrogates were tested in the IQT at different charge air temperatures, and the results of the tests were compared with those for the target JP-8. The surrogate that best reproduced the auto-ignition and combustion characteristics of the target JP-8 in the IQT was then selected for its validation in a single cylinder direct injection research diesel engine operating at different conditions. The similarities between the auto-ignition, combustion, and emissions characteristics of the surrogate and the target JP-8 were then examined to underscore the validity of the surrogate development approach as well as the use of the IQT for surrogate development and preliminary validation. Finally, a reduced chemical mechanism of the surrogate was developed for its use with the CFD codes for diesel engine cycle simulation. </p><p> The IQT tests showed that the two-component surrogate S2 best reproduced the autoignition and combustion characteristics of the target JP-8. The results of the engine validation tests indicated that the surrogate S2 closely reproduced the autoignition, combustion, and emissions characteristics (Carbon Monoxide, unburned hydrocarbons, and oxides of Nitrogen) of the target JP-8 at the tested conditions. However, the particulate matter concentrations were lower for the surrogate than for the target JP-8. Further, the results of the 3D CFD simulation, which utilized the reduced chemical mechanism of the surrogate S2, were in fairly good agreement with the autoignition, combustion, and emissions data of the surrogate S2 obtained from engine experiments.</p>

<p> Analytical solutions of periodic motions in a periodically excited, Duffing oscillator with a time-delayed displacement are developed through the Fourier series, and the stability and bifurcation of such periodic motions are discussed through eigenvalue analysis. The analytical bifurcation trees of period-1 motions to chaos in the time-delayed Duffing oscillator is presented through asymmetric period-1 to period-4 motions. Four independent symmetric period-3 motions were obtained. Two independent symmetric period-3 motions are not relative to chaos, while the other two includes bifurcation trees of period-3 motion to chaos, which are presented through period-3 to period-6 motions. Stable periodic motions are illustrated from numerical and analytical solutions. The appropriate initial history functions for periodic motions are analytically computed from the analytical solutions of periodic motions. Without the appropriate initial history functions, such a time-delayed system cannot yield periodic motions directly.</p>

<p> Large-eddy simulations of turbulent flows past a circular cylinder have been performed at sub-, critical and super-critical Re using an orthogonal curvilinear grid solver, CFDship-Iowa version 6.2. An extensive verification and validation study has been carried out. Various aspects of the flow field have been investigated. </p><p> The aspect ratio of the computational domain has major effects on the results. In general, large aspect ratio produced best results for the sub-critical Re. Small dependency on both aspect ratio and grid resolution was observed for the critical Re. Small aspect ratio and conservative scheme produced best results for the super-critical Re. </p><p> Overall flow features and the drag crisis phenomenon have been correctly predicted. A lot of experimental and numerical studies of flow past a circular cylinder were collected and used for the validation of the present LES study. Integral and local variables were in fairly good agreement for the sub-critical Re. Sharp behavior including drag crisis was predicted for the critical Re. Although some discrepancy including early formation of turbulent separation was observed, local flow structures including separation bubble were observed for the super-critical Re. </p><p> The formation of secondary vortex near the cylinder wall and its evolution into separation bubble were observed. The spectral analysis showed that the separation bubble had the instabilities close to the shear layer frequency. The proximity of shear layer to the cylinder enhanced the mixing process of boundary layer and shear layer and led to the formation of separation bubble. A snapshot POD method was used to extract flow structures in the boundary layer, shear layer and wake. In the boundary layer, the secondary vortices and separation bubble were successfully extracted. Due to the weak TKE distribution, specific flow structures were hard to find in the shear layer. Large two-dimensional flow structures representing the Karman shedding vortices were extracted for the sub- and super-critical Re.</p>

This research presents automatic aerodynamic shape optimization results for the NREL S809 wind turbine profile. The objective of this re-design was to improve the total lift to drag ratio for steady low-Mach number flows. This research sets the groundwork for the development of a multidisciplinary optimization framework for complete wind turbine rotors. To develop the aerodynamic design framework for the wind turbine applications, low-Mach preconditioning and Menter's k-omega SST turbulence model have been implemented into the flow solver. A preconditioned discrete viscous adjoint-based automatic aerodynamic optimization method has been developed and validated. Various design case studies of the NREL Phase VI blade, at different free-stream Mach numbers, have been conducted. / Ce projet de recherche présente les résultats d'une méthode d'optimisation automatique de formes aérodynamiques, appliquée aux profils de l'éolienne NREL S809. L'objectif de cette reconception est d'améliorer le rapport portance sur traîné e dans le cas d'écoulements stationnaires à faible nombre de Mach. Ce projet de recherche définit les bases de travail pour le développement de méthodes et d'outils d'optimisation multidisciplinaire de rotors d'éolienne. Dans ce cadre de conception aérodynamique appliquée aux éoliennes, un préconditionneur pour faible nombre de Mach ainsi que le modèle de turbulence k-omega SST de Menter ont été implémentés dans le modèle numérique de simulation de mécanique des fluides. Une méthode adjointe discrète préconditionnée automatique d'optimisation aérodynamique pour les fluides visqueux a été développée et validée. Plusieurs études de cas de conception de la pale NREL Phase VI ont été effectuées pour différents Mach infini-amonts.

The vast majority of mollusks grow a hard shell for protection. Typical seashells are composed of two distinct layers, with an outer layer made of calcite (a hard but brittle material) and an inner layer made of a tough and ductile material called nacre. Nacre is a biocomposite material that consists of more than 95% of tablet-shape aragonite, CaCO3, and a soft organic material as matrix. Although the brittle ceramic aragonite composes a high volume fraction of nacre, its mechanical prop-erties are found to be surprisingly higher than those of its constituents. It has been suggested that calcite and nacre, two materials with distinct structures and proper-ties, are arranged in an optimal fashion to defeat attacks from predators. This re-search aims at exploring this hypothesis by capturing the design rules of a gastro-pod seashell using multiscale modeling and optimization techniques. At the mi-croscale, a representative volume element of the microstructure of nacre was used to formulate an analytical solution for the elastic modulus of nacre, and a multiax-ial failure criterion as a function of the microstructure. At the macroscale, a two-layer finite element model of the seashell was developed to include shell thick-ness, curvature and calcite/nacre thickness ratio as geometric parameters. The maximum load that the shell can carry at its apex was obtained. A multiscale op-timization approach was also employed to evaluate whether the natural seashell is optimally designed. Finally, actual penetration experiments were performed on red abalone shells to validate the results. / Une vaste majorité des mollusques développent une coquille dure pour leur pro-tection. Une coquille typique est constitué de deux couches distinctes. La couche externe est faite de calcite (un matériau dur mais fragile), tandis que la couche in-terne est composée de nacre, un matériau plus résiliant et ductile. La nacre est un matériau biocomposite constitué de plus de 95% d'aragonite sous forme de ta-blette et d'un matériel organique souple qui forme la matrice. Bien que la cérami-que aragonite constitue une grande portion de la nacre, ses propriétés mécaniques sont étonnamment plus élevées de celles de ses constituants. La calcite et la nacre, deux matériaux avec des propriétés et des structures différentes, sont supposément étalonnées de façon optimale pour combattre les attaques de prédateurs. Cette étude cherche à déterminer les règles de construction d'une coquille de gastropode en utilisant la modélisation multi-échelle et des techniques d'optimisation. À l'échelle microscopique, un volume représentatif de la microstructure de la nacre a été utilisé pour formuler une solution analytique de son module d'élasticité et un critère de fracture multiaxial fonction des dimensions de la microstructure. À l'échelle macroscopique, un modèle d'éléments finis à deux couches de la co-quille à été utilisé pour représenter la curvature et le ratio calcite/nacre en fonction des paramètres géométriques. La charge maximale que la coquille peut supporter à son apex a été déterminée. Une approche d'optimisation multi-échelle a aussi été employée pour évaluer la reconstruction optimale du coquillage naturel. Fina-lement, plusieurs tests ont été effectués sur une coquille d'abalone rouge pour valider les résultats.

The kinematics and dynamics for the purposes of analysis, control, simulation, and design of general platform-type parallel manipulators are the subject of this thesis. / Two new methods of direct kinematics for displacement analysis are proposed. Velocity and acceleration analyses for general kinematic architectures are fully studied. Furthermore, kinematic singularities are classified based on their nature. Architecture singularities and architecture conditioning are deeply studied and incorporated into design strategies, along with design examples. Moreover, formulation singularities are also given due attention with case studies. / In dynamics modelling, the method of the natural orthogonal complement is applied such that the resulting models are structurally algorithmic, computationally efficient, and numerically robust--essential properties for the implementation of more sophisticated control strategies. Efficient inverse and direct dynamics algorithms are developed based on the dynamics models in both joint space and Cartesian space. The algorithms have been implemented with a general software package that is available for dynamics control and motion simulation of platform manipulators. As practical applications, the dynamics modelling and simulation of some commercial flight simulators are included. / Finally, the concept of dynamic isotropy is introduced, which allows one to evaluate the motion/force performance of a manipulator with respect to control and simulation. Application strategies of this concept to some robotics problems such as design, trajectory planning, and inverse kinematics are discussed, along with examples.

This thesis describes a novel approach to the analysis of fatigue crack closure phenomena. Based on the proposed model, the combined effect of residual plastic stretch, asperity mismatch, and corrosion debris on the closure behavior of a fatigue crack can be simulated by a hypothetical rigid insert located in an ideal crack wake. Accordingly, the crack closing period can be modeled by a gradual contact between the ideal crack faces and the rigid insert. / The formulation of the model results in a set of equations which can predict the closure load as well as the load-CMOD characteristics using the residual CMOD at zero load as a unique experimental input. Based on the initial model, the final form of the derived equations are either logarithmic or quadratic. While the latter can be solved directly for the closure load, the former requires a numerical solution. / The model qualitatively predicts the effect of gradual crack wake removal on the crack closure load level and the load-CMOD behavior. It also accounts for the response of a cracked component to an anomalous crack wake formed by single or block overloads. / The model is verified, both qualitatively and quantitatively, using specifically designed experimental techniques, a variety of specimen sizes, and two different alloys.