In this paper, we consider the well-known Fattorini’s criterion for approximate controllability of infinite dimensional linear systems of type ′ = + . We precise the result proved by Fattorini in [H.O. Fattorini, 4 (1966) 686–694.] for bounded input , in the case where can be unbounded or in the case of finite-dimensional controls. More precisely, we prove that if Fattorini’s criterion is satisfied and if the set of geometric multiplicities of is bounded then approximate controllability can be...
In this paper, we consider the interaction between a rigid body and an incompressible, homogeneous, viscous fluid. This fluid-solid system is assumed to fill the whole space , or . The equations for the fluid are the classical Navier-Stokes equations whereas the motion of the rigid body is governed by the standard conservation laws of linear and angular momentum. The time variation of the fluid domain (due to the motion of the rigid body) is not known , so we deal with a free boundary value...
We propose a numerical scheme to compute the motion of a two-dimensional rigid body in a viscous fluid. Our method combines the method of characteristics with a finite element approximation to solve an ALE formulation of the problem. We derive error estimates implying the convergence of the scheme.
In this paper we study a controllability problem for a simplified one dimensional model for the motion of a rigid body in a viscous fluid. The control variable is the velocity of the fluid at one end. One of the novelties brought in with respect to the existing literature consists in the fact that we use a single scalar control. Moreover, we introduce a new methodology, which can be used for other nonlinear parabolic systems, independently of the techniques previously used for the linearized problem....
The topological sensitivity analysis consists in studying the behavior of a given shape functional when the topology of the domain is perturbed, typically by the nucleation of a small hole. This notion forms the basic ingredient of different topology optimization/reconstruction algorithms. From the theoretical viewpoint, the expression of the topological sensitivity is well-established in many situations where the governing p.d.e. system is of elliptic type. This paper focuses on the derivation...
We consider the motion of a rigid body immersed in an incompressible perfect fluid which occupies a three-dimensional bounded domain. For such a system the Cauchy problem is well-posed locally in time if the initial velocity of the fluid is in the Hölder space . In this paper we prove that the smoothness of the motion of the rigid body may be only limited by the smoothness of the boundaries (of the body and of the domain). In particular for analytic boundaries the motion of the rigid body is analytic...
The topological sensitivity analysis consists in studying the behavior of a given shape functional when the topology of the domain is perturbed, typically by the nucleation of a small hole. This notion forms the basic ingredient of different topology optimization/reconstruction algorithms. From the theoretical viewpoint, the expression of the topological sensitivity is well-established in many situations where the governing p.d.e. system is of elliptic type. This paper focuses on the derivation...
We consider the approximation of a class of
exponentially stable infinite dimensional linear systems modelling
the damped vibrations of one dimensional vibrating systems or of
square plates. It is by now well known that the approximating
systems obtained by usual finite element or finite difference are
not, in general, uniformly stable with respect to the discretization
parameter. Our main result shows that, by adding a suitable
numerical viscosity term in the numerical scheme, our approximations
are...
In this paper we investigate the motion of a rigid ball in an incompressible perfect fluid occupying . We prove the global in time existence and the uniqueness of the classical solution for this fluid-structure problem. The proof relies mainly on weighted estimates for the vorticity associated with the strong solution of a fluid-structure problem obtained by incorporating some dissipation.
In this paper we investigate the motion of a rigid ball in an
incompressible perfect fluid occupying .
We prove the global in time existence and the uniqueness of
the classical solution for this fluid-structure problem. The proof relies
mainly on weighted estimates for the vorticity associated with
the strong solution of a fluid-structure problem
obtained by incorporating some dissipation.
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