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Статті в журналах з теми "Mécanique computationnelle":
GHIȚĂ, Andreea. ""LA PREMIÈRE RELANCE DE LA TA – UNE APPROCHE « INDIRECTE »"." Professional Communication and Translation Studies 15, no. 2022 (2022): 108–18. http://dx.doi.org/10.59168/wnov2053.
Bishop, P. J., A. Falisse, F. De Groote, and J. R. Hutchinson. "Predictive Simulations of Musculoskeletal Function and Jumping Performance in a Generalized Bird." Integrative Organismal Biology 3, no. 1 (January 1, 2021). http://dx.doi.org/10.1093/iob/obab006.
Дисертації з теми "Mécanique computationnelle":
Mosquera, Meza Rolando. "Interpolation sur les variétés grassmanniennes et applications à la réduction de modèles en mécanique." Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS008/document.
This dissertation deals with interpolation on Grassmann manifolds and its applications to reduced order methods in mechanics and more generally for systems of evolution partial differential systems. After a description of the POD method, we introduce the theoretical tools of grassmannian geometry which will be used in the rest of the thesis. This chapter gives this dissertation a mathematical rigor in the performed algorithms, their validity domain, the error estimate with respect to the grassmannian distance on one hand and also a self-contained character to the manuscript. The interpolation on Grassmann manifolds method introduced by David Amsallem and Charbel Farhat is afterward presented. This method is the starting point of the interpolation methods that we will develop in this thesis. The method of Amsallem-Farhat consists in chosing a reference interpolation point, mapping forward all interpolation points on the tangent space of this reference point via the geodesic logarithm, performing a classical interpolation on this tangent space and mapping backward the interpolated point to the Grassmann manifold by the geodesic exponential function. We carry out the influence of the reference point on the quality of the results through numerical simulations. In our first work, we present a grassmannian version of the well-known Inverse Distance Weighting (IDW) algorithm. In this method, the interpolation on a point can be considered as the barycenter of the interpolation points where the used weights are inversely proportional to the distance between the considered point and the given interpolation points. In our method, denoted by IDW-G, the geodesic distance on the Grassmann manifold replaces the euclidean distance in the standard framework of euclidean spaces. The advantage of our algorithm that we show the convergence undersome general assumptions, does not require a reference point unlike the method of Amsallem-Farhat. Moreover, to carry out this, we finally proposed a direct method, thanks to the notion of generalized barycenter instead of an earlier iterative method. However, our IDW-G algorithm depends on the choice of the used weighting coefficients. The second work deals with an optimal choice of the weighting coefficients, which take into account of the spatial autocorrelation of all interpolation points. Thus, each weighting coefficient depends of all interpolation points an not only on the distance between the considered point and the interpolation point. It is a grassmannian version of the Kriging method, widely used in Geographic Information System (GIS). Our grassmannian Kriging method require also the choice of a reference point. In our last work, we develop a grassmannian version of Neville's method which allow the computation of the Lagrange interpolation polynomial in a recursive way via the linear interpolation of two points. The generalization of this algorithm to grassmannian manifolds is based on the extension of interpolation of two points (geodesic/straightline) that we can do explicitly. This algorithm does not require the choice of a reference point, it is easy to implement and very quick. Furthermore, the obtained numerical results are notable and better than all the algorithms described in this dissertation
Flament, Théo. "Modèle d'ordre réduit de structures non-linéaires pour l'aéroélasticité des turbomachines." Electronic Thesis or Diss., Paris, HESAM, 2023. http://www.theses.fr/2023HESAC038.
This work concerns the development of a reduced order model for geometric nonlinear structures, to replace the nonlinear structure solver within the framework of partitioned coupling for the numerical resolution of fluid-structure interaction problems, and thus the prediction of aeroelasticity phenomena encountered in turbomachinery. The construction of the reduced order model is based on a projection of the equations into a basis of reduced dimension, containing both linear modes of the structure and dual modes. The purpose of the latter is to enhance the basis of linear normal modes in order to capture the non-linearity. An original method for calculating the coefficients of the non-linear forces projected into this basis is also proposed. Forces are imposed on the structure, as opposed to the usual approach of imposed displacements. The same loading cases can thus be used to determine both the dual modes and the coefficients of the projected non-linear forces.In this thesis, the methodology to build the reduced order model is detailed. It is first validated on a simple case of a nonlinear Euler-Bernoulli beam subjected to different loading conditions, including a partitioned fluid-structure coupling involving vortex-induced vibrations. The ability of this reduced order model to replace a nonlinear finite element solver is demonstrated in this last application. Validation on 3D cases is also proposed, including the complex geometry of a realistic engine fan blade subjected to unsteady aerodynamic loading
Jurczuk, Krzysztof. "Calcul parallèle pour la modélisation d'images de résonance magnétique nucléaire." Thesis, Rennes 1, 2013. http://www.theses.fr/2013REN1S089.
This PhD thesis concerns computer modeling of magnetic resonance imaging (MRI). The main attention is centered on imaging of vascular structures. Such imaging is influenced not only by vascular geometries but also by blood flow which has to been taken into account in modeling. Next to the question about the quality of developed models, the challenge lies also in the demand for high performance computing. Thus, in order to manage computationally complex problems, parallel computing is in use. In the thesis three solutions are proposed. The first one concerns parallel algorithms of vascular network modeling. Algorithms for different architectures are proposed. The first algorithm is based on the message passing model and thus, it is suited for distributed memory architectures. It parallelizes the process of connecting new parts of tissue to existing vascular structures. The second algorithm is designed for shared memory machines. It also parallelizes the perfusion process, but individual processors perform calculations concerning different vascular trees. The third algorithm combines message passing and shared memory approaches providing solutions for hybrid parallel architectures. Developed algorithms are able to substantially speed up the time-demanded simulations of growth of complex vascular networks. As a result, more elaborate and precise vascular structures can be simulated in a reasonable period of time. It can also help to extend the vascular model and to test multiple sets of parameters. Secondly, a new approach in computational modeling of magnetic resonance (MR) flow imaging is proposed. The approach combines the flow computation by lattice Boltzmann method, MRI simulation by following discrete local magnetizations in time and a new magnetization transport algorithm together. Results demonstrate that such an approach is able to naturally incorporate the flow influence in MRI modeling. As a result, in the proposed model, no additional mechanism (unlike in prior works) is needed to consider flow artifacts, what implies its easy extensibility. In combination with its low computational complexity and efficient implementation, the solution is a user-friendly and manageable at different levels tool which facilitates running series of simulations with different physiological and imaging parameters. The goal of the third solution is to apply the proposed MR flow imaging model on complex vascular networks. To this aim, models of vascular networks, flow behavior and MRI are combined together. In all the model components, computations are adapted to be performed at various parallel architectures. The model potential and possibilities of simulations of flow and MRI in complex vascular structures are shown. The model aims at explaining and exploring MR image formation and appearance by the combined knowledge from many processes and systems, starting from vascular geometry, through flow patterns and ending on imaging technology
Mari, Raphaël. "Influence of heat transfer on high pressure flame structure and stabilization in liquid rocket engines." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/15616/1/Mari_1.pdf.
Xie, Xiaomin. "Investigation of Local and Global Hydrodynamics of a Dynamic Filtration Module (RVF Technology) for Intensification of Industrial Bioprocess." Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0020/document.
This thesis focuses on the understanding and the control of dynamic interactions between physical and biological mechanisms considering an alternative membrane separation into industrial bioprocess. It aims to carry scientific knowledge related to the control of bioreaction considering complex hydrodynamics and retention-permeation locks specific to membrane separation. A dynamic filtration technology, called Rotating and Vibrating Filtration (RVF), was investigated. It consists of filtration cells in series including two flat disc membranes fixed onto porous substrates in the vicinity of a three-blade impeller attached to a central shaft. This simple mechanical device runs continuously and generates a high shear stress as well as a hydrodynamic perturbation in the narrow membrane-blade gap. Several scientific and technical locks motivating this work are to characterize and to quantify (i) the velocity fields locally and instantaneously, (2) the shear stresses at membrane surface and (3) the mechanical impact on microbial cells.To this end, experiments and numerical simulations have been performed to investigate the hydrodynamics at global and local scales under laminar and turbulent regimes with Newtonian fluids under biotic and abiotic environment. For global approach, investigation of Residence Time Distribution (RTD) and thermal balance was carried out and compared to the previous global study (power consumption and friction curves). Analytical study of distribution functions was conducted and statistical moments were calculated and discussed. A systemic analysis was used to describe the hydrodynamic behaviors of the RVF module. Combining Computational Fluid Dynamics (CFD) and RTD observations, it leads to demonstrate dysfunctioning conditions and area. For the local approach, Particle Image Velocimetry (PIV) was be carried out in both horizontal and vertical planes and compared to CFD simulation. PIV preliminary study was conducted with a trigger strategy to access through angle-resolved measurements to an averaged velocity field. PIV further study were performed with a non-trigger strategy and applied to Proper Orthogonal Decomposition (POD) analysis in order to identify the coherent structure of the flow by decomposing the organized and turbulent fluctuations. For the bioprocess application, an exploratory work characterized the effect of Dynamic Filtration on prokaryote cell population (Escherichia coli) by quantifying cell integrity or damage as a function of time and rotation speed during filtration process in turbulent regime
Magin, Thierry. "A model for inductive plasma wind tunnels." Doctoral thesis, Universite Libre de Bruxelles, 2004. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211179.
equilibrium are computed from the semi-classical statistical mechanics.
The electromagnetic and hydrodynamic fields of an inductive wind tunnel is presented. A total pressure measurement technique is thoroughly investigated by means of numerical simulations.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Sanz, Garcia Juan. "Theoretical study of new nitrosyl ruthenium complexes : mechanisms of photoisomerization and photorelease of NO." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30160/document.
Over the last few decades, metal-nitrosyl complexes have gained an ever-growing interest among the pharmaceutical, chemical and material-science communities. This interest arises from their unique physicochemical properties, namely their response to light perturbation. Upon light irradiation, these compounds are able to release the nitric oxide radical, a signaling molecule in the vascular and other important physiological systems. It comes as no surprise that molecules with such properties have drawn the attention of the medical community for its potential use in photodynamic therapy treatment of several diseases such as cancer. This liability of nitric oxide can also be controlled with purely chemical redox reactions, with no electromagnetic perturbations. Reduction of the metal-nitrosyl moiety may trigger the cleavage of NO. Indeed, molecules that show charge transfer bands from a ligand to the metal-nitrosyl moiety in their UV-Vis absorption spectra afford photorelease quantum yields orders of magnitude larger than those who do not. This charge transfer may be considered as a M-NO reduction. Another important property shown by these metal-nitrosyl complexes is their extraordinary photochromic response to electromagnetic irradiation. In solid crystals, the changing color is due to a rearrangement of the NO ligand, going back and forth from the nitrosyl (N-bound) to the isonitrosyl (O-bound) forms. With the appropriate wavelength, the direction of the photoinduced linkage isomerization (forward and backwards) can be controlled. This feature is very appealing for the design of new high-capacity optical storage devices. One of the main goals of this PhD is to unravel the photochemical mechanisms behind both the photoisomerization and the photorelease phenomena of ruthenium-nitrosyl complexes. In order to shed some light into these processes, a full characterization of the electronic structures and potential energy surfaces of the ground and lowest excited states is required. Density Functional Theory calculations have proven to be suitable for the rationalization of the full photoinduced linkage isomerization mechanism of the trans-[RuCl(NO)(py)4]2+ molecule, a complex that yields one of the highest photoconversion rates (ca. 100%) observed among this family of complexes. The full characterization of the singlet ground state and of the lowest triplet excited state, as well as the identification of multiple crossings, allowed the establishment of the sequential two-photon absorption mechanism, involving a sideways-bonded metastable state. This predicted mechanistic picture has been confirmed by very recent experimental data