Eulerian chemical transport models are extensively used to steer environmental policy, forecast air quality and study atmospheric processes. However, the ability of these models to simulate concentrated atmospheric plumes, including fire-related smoke, may be limited. Wildland fires are important sources of air pollutants and can significantly affect air quality. Emissions released in wildfires and prescribed burns have been known to substantially increase the air pollution burden at urban locations across large regions. Air quality forecasts generated with numerical models can provide valuable information to environmental regulators and land managers about the potential impacts of fires. Eulerian models present an attractive framework to simulate the transport and transformation of fire emissions. Still, the limitations inherent to chemical transport models when applied to replicate smoke plumes must be identified and well understood to adequately interpret results and further improve the models' predictive skills. Here, a modeling framework centered on the Community Multiscale Air Quality modeling system (CMAQ) is used to simulate several fire episodes that occurred in the Southeastern U.S. and investigate the sensitivity of fine particulate matter concentration predictions to various model inputs and parameters. Significant sources of uncertainty in the model are identified and discussed, including the spatiotemporal allocation of fire emissions and meteorological drivers. In addition, special attention is given to model grid resolution. Adaptive grid modeling is explored as a strategy to simulate fire-related plumes. An adaptive version of CMAQ, capable of dynamically restructuring the grid on which solution fields are estimated and providing refinement at the regions where accuracy is most dependent on resolution, is presented. The fully adaptive three-dimensional modeling technique can be applied to reach unprecedented levels of grid resolution and provide insight into plume dynamics unattainable with static grid models. Through this work the capability of current chemical transport models to replicate fire-related air quality impacts is evaluated, key research needs to achieve effective simulations are identified, and numerical tools designed to improve model performance are developed.

In this thesis, chemically reacting flows are studied mainly for detonation problems under 1D, cylindrical and spherical symmetry conditions. The mathematical formulation of chemically reacting, inviscid, unsteady flows with species conservation equations and finite-rate chemistry is described. The Euler equations with finite-rate chemistry are discretized by Finite-Volume method and solved implicitly by using a time-spliting method. Inviscid fluxes are computed using Roe Flux Difference Splitting Model. The numerical solution is implemented in parallel using domain decomposition and PVM library routines for inter-process communication. The solution algorithm is validated first against the numerical and experimental data for a shock tube problem with and without chemical reactions and for a cylindrical and spherical propagation of a shock wave. 1D, cylindrically and spherically symmetric detonations of H2:O2:Ar mixture are studied next.

iv In this thesis, numerical solutions of a 2D stator compressor cascade at a given inlet Mach number (0.7) and four values of incidence (49&deg / , 51&deg / , 53&deg / and 55&deg / ) are obtained. Reynolds averaged, thin layer, compressible Navier Stokes equations are solved. Different grid types have been generated. Finite differencing approach and LU - ADI splitting technique are used. Three block parallel Euler and Navier Stokes solutions are compared with the experimental results. Baldwin-Lomax turbulence model is used in the turbulent predictions and boundary layer comparisons and numerical results are in good agreement with the experiment. On the last part of the study, a rotor wake in the inlet flow has been introduced in the steady and unsteady analyses. The influence of this wake and the wake location in the inlet flow, to the total force and pressure is presented. The results have been showed that there is a relationship between the wake position and the incidence value of the case.

A Cartesian method for solution of the steady two-dimensional Euler equations is produced. Dynamic data structures are used and both geometric and solution-based adaptations are applied. Solution adaptation is achieved through solution-based gradient information. The finite volume method is used with cell-centered approach. The solution is converged to a steady state by means of an approximate Riemann solver. Local time step is used for convergence acceleration. A multistage time stepping scheme is used to advance the solution in time. A number of internal and external flow problems are solved in order to demonstrate the efficiency and accuracy of the method.

This thesis deals with developing a thermodynamically consistent model to simulate the electromechanical response of ionic polymer-metal composites based on Euler-Bernoulli beam theory. Constitutive assumptions are made for the Helmholtz free energy and the rate of dissipation. The governing equations involving small deformations are formulated using the conservation laws, the power theorem, and the maximum rate of dissipation hypothesis. The model is extended to solve large deformation cantilever beams involving pure bending which could be used in the characterization of the material parameters. A linear finite element solution along with a staggered time stepping algorithm is provided to numerically solve the governing equations of the small deformations problem under generalized electromechanical loading and boundary conditions. The results are in qualitative and quantitative agreement with the experiments performed on both Nafion and Flemion based Ionic Polymer-Metal Composite strips.

Environmental, aesthetic and political pressures continue to push for siting off-shore wind turbines beyond sight of land, where waters tend to be deeper, and use of floating structures is likely to be considered. Savings could potentially be realized by reducing hull size, which would allow more compliance with the wind thrust force in the pitch direction. On the other hand, these structures with large-amplitude motions will make dynamic analysis both more challenging and more critical. Prior to the present work, there were no existing dynamic simulation tools specifically intended for compliant wind turbine design. Development and application of a new computational method underlying a new time-domain simulation tool is presented in this dissertation. The compliant floating wind turbine system is considered as a multibody system including tower, nacelle, rotor and other moving parts. Euler's equations of motion are first applied to the compliant design to investigate the large-amplitude motions. Then, a new formulation of multibody dynamics is developed through application of the conservation of both linear momentum and angular momentum to the entire system directly. A base body is prescribed within the compliant wind turbine system, and the equations of motion (EOMs) of the system are projected into the coordinate system associated with this body. Only six basic EOMs of the system are required to capture 6 unknown degrees of freedom (DOFs) of the base body when mechanical DOFs between contiguous bodies are prescribed. The 6 x 6 mass matrix is actually composed of two decoupled 3 x 3 mass matrices for translation and rotation, respectively. Each element within the matrix includes the inertial effects of all bodies. This condensation decreases the coupling between elements in the mass matrix, and so minimizes the computational demand. The simulation results are verified by critical comparison with those of the popular wind turbine dynamics software FAST. The new formulation is generalized to form the momentum cloud method (M- CM), which is particularly well suited to the serial mechanical N-body systems connected by revolute joints with prescribed relative rotation. The MCM is then expanded to multibody systems with more complicated joints and connection types.

Zugl.: Zürich, Univ., Diss., 2006

Stuttgart, Univ., Diss., 2007. / Druckausg. beim Hut Verl., München erschienen.

Th. doct.--Sci. de l'ingénieur--Nice-Sophia Antipolis, 1995. / Bibliogr. p. 7-8 et p. 173-177. Résumé en français et en anglais. 1996 d'après la déclaration de dépÔt légal.

Stuttgart, Univ., Diss., 2002.