Thèse (D.Eng.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.

Title: Solution of inverse problem for a flow around an airfoil Author: Mgr. Jan Šimák Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Miloslav Feistauer, DrSc., dr. h. c., Department of Numerical Mathematics Abstract: The method described in this thesis deals with a solution of an inverse problem for a flow around an airfoil. It can be used to design an airfoil shape according to a specified velocity or pressure distribution along the chord line. The method is based on searching for a fixed point of an operator, which combines an approximate inverse and direct operator. The approximate inverse operator, derived on the basis of the thin airfoil theory, assigns a corresponding shape to the specified distribution. The resulting shape is then constructed using the mean camber line and thickness function. The direct operator determines the pressure or velocity distribution on the airfoil surface. We can apply a fast, simplified model of potential flow solved using the Fredholm integral equation, or a slower but more accurate model of RANS equations with a k-omega turbulence model. The method is intended for a subsonic flow.

This dissertation describes efforts to evaluate a recently proposed continuum model for the dense flow of dry granular materials (Jop, Forterre & Pouliquen, 2006, Nature, 441, 167-192). The model, based upon a generalisation of Coulomb sliding friction, is known to perform well when modelling certain simple free surface flows. We extend the application of this model to a wide range of flow configurations, beginning with six simple flows studied in detailed experiments (GDR MiDi, 2004, Eur. Phys. J. E, 14, 341-366). Two-dimensional shearing flows and problems of linear stability are also addressed. These examples are used to underpin a thorough discussion of the strengths and weaknesses of the model. In order to calculate the behaviour of granular material in more complicated configurations, it is necessary to undertake a numerical solution. We discuss several computational techniques appropriate to the model, with careful attention paid to the evolution of any shear-free regions that may arise. In addition, we develop a numerical scheme, based upon a marker-and-cell method, that is capable of modelling two-dimensional granular flow with a moving free surface. A detailed discussion of our unsuccessful attempt to construct a scheme based upon Lagrangian finite elements is presented in an appendix. We apply the marker-and-cell code to the key problem of granular slumping (Balmforth & Kerswell, 2005, J. Fluid Mech., 538, 399-428), which has hitherto resisted explanation by modelling approaches based on various reduced (shallow water) models. With our numerical scheme, we are able to lift the assumptions required for other models, and make predictions in good qualitative agreement with the experimental data. An additional chapter describes the largely unrelated problem of contact between two objects separated by a viscous fluid. Although classical lubrication theory suggests that two locally smooth objects converging under gravity will make contact only after infinite time, we discuss several physical effects that may promote contact in finite time. Detailed calculations are presented to illustrate how the presence of a sharp asperity can modify the approach to contact.

Orientador: Antonio Carlos Bannwart / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-22T07:33:01Z (GMT). No. of bitstreams: 1 Paternost_GuilhermeMiranda_M.pdf: 4957872 bytes, checksum: 34efcf3e5536aa84d89fa2b289df6cee (MD5) Previous issue date: 2013 / Resumo: O bombeio centrífugo submerso (BCS) é o segundo método de elevação artificial mais utilizado em poços de petróleo no mundo. Nestes poços, o equipamento está sujeito à influência de fluidos viscosos e à presença de gás livre, os quais impactam significativamente seu desempenho já que este é resultado da dinâmica de fluidos nos impelidores e difusores da bomba. Historicamente, devido ao escoamento de gás e de fluidos viscosos se tratarem de situações distintas, as maiorias dos estudos realizados analisam estes fenômenos separadamente vistos a complexidade e particularidades existentes de cada. O objetivo deste trabalho é a realização de um estudo experimental de avaliação do desempenho de uma bomba centrífuga sob os dois fenômenos, onde foi mensurado o impacto e a interação das principais variáveis que afetam seu desempenho. Para isto, foi construída uma bancada experimental constando de uma bomba centrífuga do tipo voluta, permitindo medir seu desempenho com água e fluido viscoso juntamente com os efeitos de fração de vazio, diâmetro de bolha e pressão de entrada. Foi também avaliada uma proposta existente de mapeamento do comportamento de uma bomba centrífuga operando com escoamento monofásico em função de números adimensionais que traduzem os efeitos combinados da viscosidade e da rotação. Foram sugeridas modificações e correlações baseadas nesta proposta e seus resultados comparados aos dados experimentais obtidos / Abstract: The Electrical Submersible Pumping (ESP) is the second most commonly used artificial lift method worldwide, being responsible for the highest amount of total fluids produced (oil and water). In wells using this method, the equipment may be subjected to viscous fluids and free gas flow, both affecting pump performance since it is a result of the fluid dynamics inside its impellers and diffusers. Generally, since the presence of free gas and liquid viscosity are independent phenomena, most studies so far have examined their effect separately due to their complexity. The purpose of this experimental study is to take another step towards understanding the performance of a centrifugal pump under these two phenomena, measuring the impact of the main variables involved. A testing rig consisting of a centrifugal pump of volute type was built, where its performance was measured with the varying effects of viscosity, void fraction and rotational speed / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

A finite element method is employed for solving two- and three-dimensional incompressible flows. The formulation is based on a segregated solution method. In this segregated formulation, the velocities and pressures are uncoupled and the equations for each are solved one after the other. This segregated solution method is numerically compared to the penalty method and to previous reported data to determine its validity. Next an iterative solution method which employs an element by - element data structure of the finite element method is developed. Two types of iterative methods are used. For a symmetric stiffness matrix, the conjugate gradient method is used. For an unsymmetric stiffness matrix, the bi-conjugate gradient method is used. Both iterative solution methods make use of a diagonal preconditioning method (Jacobi preconditioning). Several problems are solved using this segregated method. In two-dimensions, flow over a backward facing step and flow in a cavity are investigated. In three-dimensions, the problems include flow in a cavity at Reynolds number 100 and 1000, and flow in a curved duct. The simulation compares very well with previously reported data, where available. / Ph. D.

Yes / Laboratory experiments have been carried out to investigate wave damping over the seabed, in which the excess pore pressure and free surface elevations are synchronously measured for examining the wave-induced soil dynamics and wave kinematics. Two types of soil, namely fine sand and silt, are tested to examine the role of soil in the wave damping. Observation of experiments shows that (i) soil liquefaction takes place for some tests with silty bed and soil particles suspend into the water layer when the bed is made of silt; (ii) sand ripples can be generated for experiments with sand bed. Measurements reveal that the wave damping greatly depends on the soil dynamic responses to wave loading and the wave damping mechanism over the silty seabed differs from that over the sand bed. On the one hand, the wave damping rate is greatly increased, when soil liquefaction occurs in the silty bed. On the other hand, the presence of sand ripples generated by oscillatory flow in the sand bed experiments also increases the wave damping to some extent. Furthermore, experimental results show that soil particle suspension in the silt bed test contributes to the wave damping. Theoretical analysis is presented to enhance discussions on the wave damping. The theoretical calculations demonstrate that the wave damping is mainly induced by the shear stress in the boundary layer for the cases when no liquefaction occurs. While for the cases when soil liquefaction takes place, the viscous flow in the liquefied layer contributes most towards to the wave damping. / the National Science Fund for Distinguished Young Scholars (Grant No. 51425901), the National Key Research and Development Program of China (2017YFC1404200), the Marine Renewable Energy Research Project of State Oceanic Administration (GHME2015GC01), and the 111 Project (Grant No. B12032)

Unsteady flow fields over a NACA 0012 at an angle of attack are investigated. The first is the classical pitching motion about the airfoil's quarter chord. The second is the flow over a fixed airfoil immersed in the wake of the pitching airfoil. Large reduced frequencies are considered. Measurements were obtained in a water tunnel by Laser-Doppler velocimetry. Ensemble-averaged velocity measurements were obtained in the vicinity of the trailing edges of both the pitching and the fixed airfoils. The flowfields in the wake and at the trailing edges of both airfoils were studied visually. The validity of the quasi-steady and an extension to an unsteady Kutta condition are examined. A new dynamic similarity parameter is proposed. An analytical method based on the dynamics of discrete vortices is employed. Numerical calculations of the flow over the fixed airfoil are compared with experimental results. / Ph. D.

A numerical method has been developed to predict the three-dimensional nonequilibrium flowfield past the space shuttle orbiter at high angles-of-attack (up to 50-deg). An existing viscous shock-layer method for perfect gas flows has been extended to include finite-rate chemical reactions of multi-component ionizing air. A general nonorthogonal computational grid system was introduced to treat the nonaxisymmetric geometry. At shuttle reentry flight conditions, nonequilibrium real gas effects on the surface-measurable quantities are significant. Computational solutions have been obtained for chemically reacting flowfields over the entire windward surface of the space shuttle orbiter at high angles-of-attack. Boundary conditions studied include noncatalytic wall, finite-catalytic wall, fully-catalytic wall, and nonequilibrium slip conditions at the wall and/or shock. The nonequilibrium solutions with a finite-catalytic wall are compared to both fully-catalytic and noncatalytic wall solutions. The present solutions are also compared to chemical equilibrium air solutions, perfect gas solutions, and the shuttle flight heating and pressure data. The comparisons show good agreement and correlations with flight-derived surface heat-transfer and pressure distributions. Three-dimensional effects are clearly shown in the flight-derived data for the first time based upon the results of this study. / Ph. D.

A computer program for predicting the three-dimensional nonequilibrium viscous shock-layer flows over blunt spherecones, straight. and bent mul ticonics at angle-of-attack has been developed. The method used is the viscous shock-layer approach- for nonequilibrium, multi-component ionizing air. A seven species chemical reaction model with single ionizing species and an eleven species chemical reaction model with five ionizing species are used to represent the chemistry. The seven species model considers 7 reactions whereas the eleven species model considers 26 reactions and the results obtained using these models are compared with perfect gas and equilibrium air results. This code is capable of analyzing shock-slip or no-shock-slip boundary conditions and equilibrium or non-catalytic wall boundary conditions. In this study the diffusion model is limited to binary diffusion. A sphere-cone-cylinder-flare with moderate flare angle, a straight biconic, and a bent biconic with seven deg. bend angle and a sphere-cone at various flight conditions are analyzed using this method. The bent biconic has been analyzed up to an angle-of-attack of 20 deg. with respect to the aft-cone axis and sample results are compared with inviscid and viscous results. The surface pressure distribution computed by this code compares well with that from a parabolized Navier-Stokes method. The diffusion heat transfer is about 15% of the total heat transfer for most cases. The aerodynamic forces and moments at the base of the body and computing time required for all cases are presented. The shock layer profiles at a streamwi se location of 8. 8 nose radii for one case computed using seven and eleven species models compare very well with each other. / Ph. D.