Philippe Ciarlet | |
---|---|
Born | 14 October 1938 Paris, France |
Alma mater | École polytechnique |
Awards | Légion d'honneur |
Scientific career | |
Fields | Mathematics |
Institutions | Pierre and Marie Curie University City University of Hong Kong |
Doctoral advisor | Richard S. Varga |
Philippe G. Ciarlet (born 14 October 1938) is a French mathematician, known particularly for his work on mathematical analysis of the finite element method. He has contributed also to elasticity, to the theory of plates and shells and differential geometry.
Philippe Ciarlet is a former student of the École Polytechnique and the École des ponts et chaussées. He completed his PhD at Case Institute of Technology in Cleveland in 1966 under the supervision of Richard S. Varga. He also holds a doctorate in mathematical sciences from the Faculty of Sciences of Paris (doctorate under the supervision of Jacques-Louis Lions in 1971).
He headed the mathematics department of the Laboratoire central des Ponts et Chaussées (1966-1973) and was a lecturer at the École polytechnique (1967-1985), professor at the École nationale des Ponts et Chaussées (1978-1987), consultant at INRIA (1974-1994). From 1974 to 2002, he was a professor at the University of Pierre et Marie Curie where he directed the laboratory of Numerical Analysis from 1981 to 1992.
He is Professor Emeritus at the University of Hong Kong, Professor at the City University of Hong Kong, [1] [2] Member of the Academy of Technology [3] in 1989, Member of the French Academy of Sciences since 1991 (in the Mechanical and Computer Sciences section), [4] Member of the Indian Academy of Sciences in 2001, Member of the European Academy of Sciences in 2003, Member of the World Academy of Sciences in 2007, Member of the Chinese Academy of Sciences in 2009, Member of the American Mathematical Society since 2012, [5] and Member of the Hong-Kong Academy of Sciences in 2015.
Numerical analysis of finite difference methods and general variational approximation methods: In his doctoral theses and early publications, Philippe Ciarlet made innovative contributions to the numerical approximation by variational methods of problems with non-linear monotonous boundaries, [6] and introduced the concepts of discrete Green functions and the discrete maximum principle, [7] [8] which have since proved to be fundamental in numerical analysis.
Interpolation theory: Philippe Ciarlet has made innovative contributions, now "classical" to Lagrange and Hermite interpolation theory in R^n, notably through the introduction of the notion of multipoint Taylor formulas. [9] This theory plays a fundamental role in establishing the convergence of finite element methods.
Numerical analysis of the finite element method: Philippe Ciarlet is well known for having made fundamental contributions in this field, including convergence analysis, the discrete maximum principle, uniform convergence, analysis of curved finite elements, numerical integration, non-conforming macroelements for plate problems, a mixed method for the biharmonic equation in fluid mechanics, and finite element methods for shell problems. His contributions and those of his collaborators can be found in his well-known book. [10]
Plate modeling by asymptotic analysis and singular disturbance techniques: Philippe Ciarlet is also well known for his leading role in justifying two-dimensional models of linear and non-linear elastic plates from three-dimensional elasticity; in particular, he established convergence in the linear case, [11] [12] and justified two-dimensional non-linear models, including the von Kármán and Marguerre-von Karman equations, by the asymptotic development method. [13]
Modeling, mathematical analysis and numerical simulation of "elastic multi-structures" including junctions: This is another entirely new field that Philippe Ciarlet has created and developed, by establishing the convergence of the three-dimensional solution towards that of a "multidimensional" model in the linear case, by justifying the limit conditions for embedding a plate. [14] [15]
Modeling and mathematical analysis of "general" shells: Philippe Ciarlet established the first existence theorems for two-dimensional linear shell models, such as those of W.T. Koiter and P.M. Naghdi, [16] and justified the equations of the "bending" and "membrane" shell; [17] [18] [19] he also established the first rigorous justification of the "shallow" two-dimensional linear shell equations and of Koiter equations, using asymptotic analysis techniques; he also obtained a new theory of existence for non-linear shell equations.
Non-linear elasticity: Philippe Ciarlet proposed a new energy function that is polyconvex (as defined by John Ball), and has proven to be very effective because it is "adjustable" to any given isotropic elastic material; [20] he has also made important and innovative contributions to the modelling of contact and non-interpenetration in three-dimensional non-linear elasticity. [21] He also proposed and justified a new non-linear Koiter-type model for non-linearly elastic hulls.
Non-linear inequalities of Korn on a surface: Philippe Ciarlet gave several new proofs of the fundamental theorem of surface theory, concerning the reconstruction of a surface according to its first and second fundamental forms. He was the first to show that a surface continuously varies according to its two fundamental forms, for different topologies, [22] notably by introducing a new idea, that of non-linear Korn inequalities on a surface, another notion that he essentially created and developed with his collaborators. [23]
Functional analysis: Philippe Ciarlet established weak forms of Poincaré's lemma and conditions of compatibility of Saint Venant, in Sobolev's spaces with negative exponents; he established that there are deep relationships between Jacques-Louis Lions' lemma, Nečas's inequality, Rham's theorem, and Bogovskii's theorem, which provide new methods to establish these results. [24]
Intrinsic methods in linearized elasticity: Philippe Ciarlet has developed a new field, that of the mathematical justification of "intrinsic" methods in linearized elasticity, where the linearized metric tensor and the linearized tensor of curvature change are the new, and only, unknowns: [25] This approach, whether for three-dimensional elasticity or for plate and shell theories, requires an entirely new approach, based mainly on the compatibility conditions of Saint-Venant and Donati in Sobolev spaces.
Intrinsic methods in non-linear elasticity: Philippe Ciarlet has developed a new field, that of the mathematical justification of "intrinsic" methods in non-linear elasticity. This approach makes it possible to obtain new existence theorems in three-dimensional non-linear elasticity. [26]
Teaching and research books: Philippe Ciarlet has written several textbooks that are now "classics ", [10] [27] [28] [29] as well as several "reference" research books. [30] [31] [32] [33]
National Order of the Legion of Honour of France:
Member or Foreign Member of the following Academies :
Prizes
Academic awards
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Solid mechanics is the branch of continuum mechanics that studies the behavior of solid materials, especially their motion and deformation under the action of forces, temperature changes, phase changes, and other external or internal agents.
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In numerical analysis, BDDC (balancing domain decomposition by constraints) is a domain decomposition method for solving large symmetric, positive definite systems of linear equations that arise from the finite element method. BDDC is used as a preconditioner to the conjugate gradient method. A specific version of BDDC is characterized by the choice of coarse degrees of freedom, which can be values at the corners of the subdomains, or averages over the edges or the faces of the interface between the subdomains. One application of the BDDC preconditioner then combines the solution of local problems on each subdomains with the solution of a global coarse problem with the coarse degrees of freedom as the unknowns. The local problems on different subdomains are completely independent of each other, so the method is suitable for parallel computing. With a proper choice of the coarse degrees of freedom (corners in 2D, corners plus edges or corners plus faces in 3D) and with regular subdomain shapes, the condition number of the method is bounded when increasing the number of subdomains, and it grows only very slowly with the number of elements per subdomain. Thus the number of iterations is bounded in the same way, and the method scales well with the problem size and the number of subdomains.
In numerical analysis, the balancing domain decomposition method (BDD) is an iterative method to find the solution of a symmetric positive definite system of linear algebraic equations arising from the finite element method. In each iteration, it combines the solution of local problems on non-overlapping subdomains with a coarse problem created from the subdomain nullspaces. BDD requires only solution of subdomain problems rather than access to the matrices of those problems, so it is applicable to situations where only the solution operators are available, such as in oil reservoir simulation by mixed finite elements. In its original formulation, BDD performs well only for 2nd order problems, such elasticity in 2D and 3D. For 4th order problems, such as plate bending, it needs to be modified by adding to the coarse problem special basis functions that enforce continuity of the solution at subdomain corners, which makes it however more expensive. The BDDC method uses the same corner basis functions as, but in an additive rather than multiplicative fashion. The dual counterpart to BDD is FETI, which enforces the equality of the solution between the subdomain by Lagrange multipliers. The base versions of BDD and FETI are not mathematically equivalent, though a special version of FETI designed to be robust for hard problems has the same eigenvalues and thus essentially the same performance as BDD.
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