Les travaux de recherche présentés dans ce manuscrit portent sur le mécanisme de remplissage et de vidange simultanés d’un local ventilé naturellement, pouvant éventuellement être rencontré dans des situations d’incendie. L’objectif de ce travail et d'améliorer la compréhension des phénomènes physiques dominants ce mécanisme, notamment, une fois que le régime stationnaire est établi à partir d’études théoriques et expérimentales. Le travail est divisé en deux parties. Dans la première partie, nous reformulons dans un premier temps le modèle théorique de Linden et al. (1990) dans le cadre de l’approximation de Boussinesq basé sur la modélisation du panache turbulent proposé par Morton et al. (1956). Ce modèle est par la suite étendue au cadre général non-Boussineq. Dans un second temps, nous proposons un nouveau modèle basé sur les solutions exactes du panache turbulent à partir des travaux de Michaux & Vauquelin (2008). Une campagne d’essais densimétriques réalisée à échelle réduite permet ensuite d’éprouver et valider ces modèles. Dans la deuxième partie de ce mémoire, nous abordons la problématique de remplissage et de vidange dans le cadre plus spécifique de l'ingénieur de la sécurité incendie (ISI) appliquée au désenfumage. Nous commençons par présenter quelques modèles de flammes panache. Ensuite, ces modèles de flammes panache sont implémenté dans un modèle de remplissage vidange et comparés aux modèles présentés dans la première partie du manuscrit. La dernière partie porte sur une campagne d'essais thermiques à l'échelle du laboratoire. Le premier modèle théorique présenté dans la première partie est confronté aux différents résultats expérimentaux. / Research works presented in this thesis deals with the filling and simultaneous emptying of a naturally ventilated room subject to a continuous source of buoyancy, for example, the problem of natural ventilation of a room containing a fire. The aim of this work is to improve from a theoretical and experimental point of view the understanding of the dominant physical phenomena of this mechanism, especially once the stationary state is reached. This work is divided into two parts. In the first "academic" part, we revisit the theoretical model developed by Linden et al. (1990) under the Boussinesq approximation, based on Morton et al. (1956) turbulent plume assumption. This model is then extended in the general non-Boussinesq case and a parametric study highlights the influence of the governing parameters on which it depends. Secondly, we propose a new model based on the exact turbulent plume solutions proposed by Michaux & Vauquelin (2008). Laboratory experiments were also conducted using a light gas air-helium mixture in order to test and validate these models. In the second part of this work, we address the problem of filling and simultaneous emptying in the more specific context of fire safety engineering applied to smoke management. We begin by presenting some engineering relations for fire plumes, which we implement in a filling emptying model. A comparison is then made between these models and those presented in the first part of the manuscript. The last part deals with a fire test campaign at the laboratory scale and on full-scale. The first theoretical model presented in the first part is confronted with different experimental results.

No description available.

Near shore hydrodynamics has been an important research area dealing with coastal processes. The nearshore coastal region is the region between the shoreline and a fictive offshore limit which usually is defined as the limit where the depth becomes so large that it no longer influences the waves. This spatially limited but highly energetic zone is where water waves shoal, break and transmit energy to the shoreline and are governed by highly dispersive and non-linear effects. An accurate understanding of this phenomena is extremely useful, especially in emergency situations during hurricanes and storms. While the shallow water assumption is valid in regions where the characteristic wavelength exceeds a typical depth by orders of magnitude, Boussinesq-type equations have been used to model near-shore wave motion. Unfortunately these equations are complex system of coupled non-linear and dispersive differential equations that have made the developement of numerical approximations extremely challenging. In this dissertation, a local discontinuous Galerkin method for Boussinesq-Green Naghdi Equations is presented and validated against experimental results. Currently Green-Naghdi equations have many variants. We develop a numerical method in one horizontal dimension for the Green-Naghdi equations based on rotational characteristics in the velocity field. Stability criterion is also established for the linearized Green-Naghdi equations and a careful proof of linear stability of the numerical method is carried out. Verification is done against a linearized standing wave problem in flat bathymetry and h,p (denoted by K in this thesis) error rates are plotted. The numerical method is validated with experimental data from dispersive and non-linear test cases. / text

This dissertation presents models for turbulent flow and transport by currents and long waves in large domain. From the Navier-Stokes equations, a fully nonlinear depth-integrated equation model for weakly dispersive, turbulent and rotational flow is derived by a perturbation approach based on long wave scaling. The same perturbation approach is applied for the derivation of a depth-integrated transport equation. As the results, coherent structures generated by the turbulence induced by the bottom friction and topography can be predicted very reasonably. The three dimensional turbulence effects are incorporated into the flow model by employing a back scatter model. The back scatter model makes it possible to predict turbulent transport: It contributes to the energy transport and the lateral turbulent diffusion through relying on the turbulent intensity, not by relying on an empirical diffusion constant. The inherent limitation of the depth-integrated transport equation, that is, the limitation for the near field prediction is recognized in the derivation and the numerical simulation. To solve the derived equation set, a highly accurate and stable finite volume scheme numerical solver is developed. Thus, the numerical solver can predict dispersive and nonlinear wave propagation with minimal error. Also, good stability is achieved enough to be applied to the dam-break flows and undular tidal bores. In addition, a robust moving boundary scheme based on simple physical conditions is presented, which can extend the applicability area of the depth-integrated models. By the comparison study with experimental data, it is expected that the numerical model can provide high confidence results for the wave and current transformations including shocks and undular bores on complex bathymetry and topography. For the accurate near field transport prediction, a three dimensional transport model in ?-coordinate coupled with the depth-integrated flow model is developed. Like the other models, this model is also intended for large domain problems, and yet efficient and accurate in the far field and near field together.

In this study, the impact of various flow models is assessed under free and forced convection: compressible versus incompressible models for a Pressurized Water Reactor, and Darcy's law vs full momentum equation for High Temperature Gas Reactor. Euler equations with friction forces and a momentum and energy source/sink are used. The geometric model consists of a one-dimensional rectangular loop system. The fluid is heated up and cooled down along the vertical legs. A pressurizer and a pump are included along the horizontal legs. The compressible model is assumed to be the most accurate model in this study. Simulations show that under forced convection compressible and incompressible models yield the same transient and steady-state. As free convection is studied, compressible and incompressible models have different transient but the same final steady-state. As Darcy's law is used, pressure and velocity steady-state profiles yield some differences compared to the compressible model both under free and forced convections. It is also noted some differences in the transient.

The Boussinesq approximation is a set of fluids equations utilized in the atmospheric and oceanographic sciences. They may be thought of as inhomogeneous, incompressible Euler or Navier-Stokes equations, where the inhomogeneous term is a scalar quantity, typically representing density or temperature, governed by a convection-diffusion equation. In this thesis, we prove local-in-time existence and uniqueness of an inviscid Boussinesq system. Furthermore, we show that under stronger assumptions, the local-in-time results can be extended to global-in-time existence and uniqueness as well. We assume the density equation contains nonzero diffusion and that our initial vorticity and density belong to a space of borderline Besov-type. We use paradifferential calculus and properties of the Besov-type spaces to control the growth of vorticity via an a priori estimate on the growth of density. This result is motivated by work of M. Vishik demonstrating local-in-time existence and uniqueness for 2D Euler equations in borderline Besov-type spaces, and by work of R. Danchin and M. Paicu showing the global well-posedness of the 2D Boussinesq system with initial data in critical Besov and Lp-spaces. / text

No description available.

The nonlinear interactions between long surface waves and interfacial waves in a two-layer fluid are studied theoretically. The fluid is density-stratified and the thicknesses of the top and bottom layers are both assumed to be shallow relative to the length of a typical surface wave and interfacial wave, respectively. A set of Boussinesq-type equations are derived for potential flow in this system. The equations are then analyzed for the dynamics of the nonlinear resonant interactions between a monochromatic surface wave and two oblique interfacial waves. The analysis uses a second order perturbation approach. Consequently, a set of coupled transient evolution equations of wave amplitudes is derived. Moreover, the effect of weak viscosity of the lower layer is incorporated in the problem and the influences of important parameters on surface and interfacial wave evolution (namely the directional angle of interfacial waves, density ratio of the layers, thickness of the fluid layers, surface wave frequency, surface wave amplitude, and lower layer viscosity) are investigated. The results of the parametric study are discussed and are generally in qualitative agreement with previous studies. In shallow water, a triad formed of surface waves (or interfacial waves) can be considered in near-resonant interaction. In contrast to the previous studies which limited the study to a triad (one surface wave and two interfacial waves or one interfacial and two surface waves), the problem is generalized by considering the nonlinear interactions between a triad of surface waves and three oblique pairs of interfacial waves. In this system, each surface wave is in near-resonance interaction with other surface waves and in exact resonance with a pair of oblique interfacial waves. Similarly, each interfacial wave is in near-resonance interaction with other interfacial waves which are propagating in the same direction. Inclusion of all the interactions considerably changes the pattern of evolution of waves and highlights the necessity of accounting for several wave harmonics. Effects of density ratio, depth ratio, and surface wave frequency on the evolution of waves are discussed. Finally, a formulation is derived for spatial evolution of one surface wave spectrum in nonlinear interaction with two oblique interfacial wave spectra. The two-layer Boussinesq-type equations are treated in frequency domain to study the nonlinear interactions of time-harmonic waves. Based on weakly two-dimensional propagation of each wave train, a parabolic approximation is applied to derive the formulation.

Internal gravity waves grow in amplitude as they propagate upwards in a non-Boussinesq fluid and weakly nonlinear effects develop due to interactions with an induced horizontal mean flow. In this work, a new derivation for this wave-induced mean flow is presented and nonlinear Schrodinger equations are derived describing the weakly nonlinear evolution of these waves in an anelastic gas and non-Boussinesq liquid. The results of these equations are compared with fully nonlinear numerical simulations. It is found that interactions with the wave-induced mean flow are the dominant mechanism for wave evolution. This causes modulational stability for hydrostatic waves, resulting in propagation above the overturning level predicted by linear theory for a non-Boussinesq liquid. Due to high-order dispersion terms in the Schrodinger equation for an anelastic gas, hydrostatic waves become unstable and break at lower levels. Non-hydrostatic waves are modulationally unstable, overturning at lower levels than predicted by linear theory.

Submitted by Renan Lourenço (lourenco@dm.ufscar.br) on 2018-05-04T15:53:45Z No. of bitstreams: 1 Dissertação de mestrado.pdf: 1232362 bytes, checksum: f9fb921c419d7628fc16331fd722a3e2 (MD5) / Rejected by Ronildo Prado (ri.bco@ufscar.br), reason: Oi Renan, Faltou inserir a folha de aprovação na dissertação ou tese. Fico no aguardo para finalizarmos o processo. Abraços Ronildo on 2018-05-15T20:14:34Z (GMT) / Submitted by Renan Lourenço (lourenco@dm.ufscar.br) on 2018-05-24T17:36:16Z No. of bitstreams: 1 Dissertação de mestrado.pdf: 1729184 bytes, checksum: 782e503e0f1dd78466748b6108a9e38e (MD5) / Rejected by Eunice Nunes (eunicenunes6@gmail.com), reason: Boa noite Renan, Verificamos que você enviou a Carta do Orientador inserida em sua dissertação. Ela deve ser enviada em um arquivo separado na mesma tela que você submeteu seu trabalho em inserir outros Upload. Como mencionei anteriormente acho que foi o software Latex que você utilizou e a folha de aprovação com os membros da Banca dever ser inserida na página três, a primeira é a Capa, a segunda é a Folha de rosto e a terceira a Folha de aprovação. Poderia por favor retificar o arquivo pois não consigo fazer a alteração. Qualquer dúvida estou à disposição Abraços Eunice on 2018-05-25T23:31:47Z (GMT) / Submitted by Renan Lourenço (lourenco@dm.ufscar.br) on 2018-05-26T15:49:56Z No. of bitstreams: 2 Dissertação de mestrado.pdf: 1418780 bytes, checksum: 4b2dfba68dacd03bd72f9210bf4793dc (MD5) ficha.pdf: 309784 bytes, checksum: e623e0f48ac3f833124a78f9429ecdf3 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-06-04T17:50:13Z (GMT) No. of bitstreams: 2 Dissertação de mestrado.pdf: 1418780 bytes, checksum: 4b2dfba68dacd03bd72f9210bf4793dc (MD5) ficha.pdf: 309784 bytes, checksum: e623e0f48ac3f833124a78f9429ecdf3 (MD5) / Approved for entry into archive by Ronildo Prado (ri.bco@ufscar.br) on 2018-06-04T17:50:24Z (GMT) No. of bitstreams: 2 Dissertação de mestrado.pdf: 1418780 bytes, checksum: 4b2dfba68dacd03bd72f9210bf4793dc (MD5) ficha.pdf: 309784 bytes, checksum: e623e0f48ac3f833124a78f9429ecdf3 (MD5) / Made available in DSpace on 2018-06-04T17:55:37Z (GMT). No. of bitstreams: 2 Dissertação de mestrado.pdf: 1418780 bytes, checksum: 4b2dfba68dacd03bd72f9210bf4793dc (MD5) ficha.pdf: 309784 bytes, checksum: e623e0f48ac3f833124a78f9429ecdf3 (MD5) Previous issue date: 2018-03-02 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / In this work we address the problem of good posture of the nonlinear partial differential equation known as the "good" Boussinesq equation in Sobolev spaces. We will present the results of good posture in both cases, the periodical, when the initial data and the solutions are periodic in the spatial variable, and the non-periodic one. / Neste trabalho abordamos o problema de boa postura da equação diferencial parcial não linear conhecida como a "boa" equação de Boussinesq em espaços de Sobolev. Apresentaremos os resultados de boa postura em ambos os casos, o periódico, quando os dados iniciais e as soluções são periódicos na variável espacial, e o não periódico.