B
J
Last name: BLUM
First name: Jacques
Email: Jacques.BLUM@univ-cotedazur.fr
Institution: UCA
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We present a new approach to the optimization of plasma scenarios in tokamaks. We formulate this task as an optimal control problem and use numerical methods for optimization problems with partial differential equation (PDE) constraints. The latter are discretized by linear finite elements and implicit Euler time stepping. Due to the...
We present a new approach to the optimization of plasma scenarios in tokamaks. We formulate this task as an optimal control problem and use numerical methods for optimization problems with partial differential equation (PDE) constraints. The latter are discretized by linear finite elements and implicit Euler time stepping. Due to the...
International audience
In this paper, we first focus our interest on the use of the variational adjoint method in a relatively simple ocean model in order to try to reconstruct the four-dimensional ocean system from altimetric surface observations of the ocean.
Nous étudions l'assimilation variationnelle de données lagrangiennes (positions des flotteurs dérivants), ainsi que leur complémentarité avec les données de profils verticaux de température, en expériences jumelles dans un modèle aux équations primitives de l'océan. La qualité de l'identification est estimée en fonction du temps, du niveau...
In this Note, we introduce a new algorithm for data assimilation problems, called the back and forth nudging (BFN) algorithm. The standard forward nudging algorithm is first studied for a linear ODE model. The backward nudging algorithm is then introduced in order to reconstruct the initial state of the system. These two algorithms are combined...
This paper deals with a new data assimilation algorithm, called Back and Forth Nudging. The standard nudging technique consists in adding to the equations of the model a relaxation term that is supposed to force the observations to the model. The BFN algorithm consists in repeatedly performing forward and backward integrations of the model with...
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In this paper, we generalize the so-called "nudging" algorithm in order to identify the initial condition of a dynamical system from experimental observations.
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Smoothers are increasingly used in geophysics. Several linear gaussian algorithms exist, and the general picture may appear somewhat confusing. This paper attempts to stand back a little, in order to clarify this picture by providing a concise overview of what the di erent smoothers really solve, and how. We start addressing this issue from a...
Smoothers are increasingly used in geophysics. Several linear gaussian algorithms exist, and the general picture may appear somewhat confusing. This paper attempts to stand back a little, in order to clarify this picture by providing a concise overview of what the di erent smoothers really solve, and how. We start addressing this issue from a...
One of the principal objectives of studying biogeochemical cycles is to obtain precise estimates of the main fluxes, such as total, new and export oceanic productions. Since models can incorporate the a priori knowledge of the most important processes, they are increasingly used for this purpose. However, biogeochemical models are characterized...
In this short paper we present the first application of the IMAS compatible code NICE to equilibrium reconstruction for ITER geometry. The inverse problem is formulated as a least square problem and the numerical methods implemented in NICE in order to solve it are presented. The results of a numerical experiment are shown: a reference...
In this short paper we present the first application of the IMAS compatible code NICE to equilibrium reconstruction for ITER geometry. The inverse problem is formulated as a least square problem and the numerical methods implemented in NICE in order to solve it are presented. The results of a numerical experiment are shown: a reference...
In this short paper we present the first application of the IMAS compatible code NICE to equilibrium reconstrution for ITER geometry. The inverse problem is formulated as a least square problem and the numerical methods implemented in NICE in order to solve it are presented. The results of a numerical experiment are shown: a reference...
Recent development of real-time equilibrium code Equinox [1] using a fixed-point algorithm [2] allow major plasma magnetic parameters to be identified in real-time, using rigorous analytical method. The code relies on the boundary flux code providing flux values on the first wall of vacuum vessel. By means of least-square minimization of...
The problem of equilibrium of a plasma in a Tokamak is a free boundary problemdescribed by the Grad-Shafranov equation in axisymmetric configurations. The right hand side of this equation is a non linear source, which represents the toroidal component of the plasma current density. This paper deals with the real time identification of this non...
This paper deals with the numerical reconstruction of the plasma current density in a Tokamak and of its equilibrium. The problem consists in the identification of a non-linear source in the 2D Grad-Shafranov equation, which governs the axisymmetric equilibrium of a plasma in a Tokamak. The experimental measurements that enable this...
We describe an algorithm for the reconstruction of the equilibrium in a Tokamak from discrete magnetic measurements. In order to solve this inverse problem we first use toroidal harmonics to compute Cauchy boundary conditions on a fixed closed contour. Then we use these Cauchy boundary conditions to solve a non-linear source identification problem.
In this paper, we propose an improvement to the Back and Forth Nudging algorithm for handling diffusion in the context of geophysical data assimilation. We detail the Diffusive Back and Forth Nudging algorithm, in which the sign of the diffusion term is changed in the backward integrations. We study the convergence of this algorithm, in...
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