convergence analysis of a projection semi implicit coupling scheme for fluid structure interaction problems in this paper we provide a convergence analysis of a projection semi implicit scheme for the simulation of fluid structure systems involving an incompressible viscous fluid the error analysis is performed on a fully discretized linear coupled problem a finite element approximation and a semi implicit time stepping strategy are respectively used for space and time discretization the fluid is described by the stokes equations the structure by the classical linear elastodynamics equations linearized elasticity plate or shell models and all changes of geometry are neglected we derive an error estimate in finite time and we prove that the time discretization error for the coupling scheme is at least sqrt delta t finally some numerical experiments that confirm the theoretical analysis are presented

numerical analysis of a linearised fluid structure interaction problem this paper describes the numerical analysis of a time dependent linearised fluid structure interaction problems involving a very viscous fluid and an elastic shell in small displacements for simplicity all changes of geometry are neglected a single variational formulation is proposed for the whole problem and generic discretisation strategies are introduced independently on the fluid and on the structure more precisely the space approximation of the fluid problem is realized by standard mixed finite elements the shell is approximated by dkt finite elements and time derivatives are approximated either by midpoint rules or by backward difference formula using fundamental energy estimates on the continuous problem written in a proper functional space on its discrete equivalent and on an associated error evolution equation we can prove that the proposed variational problem is well posed and that its approximation in space and time converges with optimal order to the continuous solution

incremental displacement correction schemes for incompressible fluid structure interaction in this paper we introduce a class of incremental displacement correction schemes for the explicit coupling of a thin structure with an incompressible fluid these methods enforce a specific robin neumann explicit treatment of the interface coupling we provide a general stability and convergence analysis that covers both the incremental and the non incremental variants their stability properties are independent of the added mass effect the superior accuracy of the incremental schemes with respect to the original non incremental variant is highlighted by the error estimates and then confirmed in a benchmark by numerical experiments

supervisory control of a class of discrete event processes this paper studies the control of a class of discrete event processes i e processes that are discrete asynchronous and possibly nondeter ministic the controlled process is described as the generator of a formal language while the controller or supervisor is constructed from the grammar of a specified target language that incorporates the desired closed loop system behavior the existence problem for a supervisor is reduced to finding the largest controllable language contained in a given legal language two examples are provided

analysis of a fluid structure interaction problem recast in an optimal control setting fluid structure interaction fsi simulation presents many computational difficulties particularly when the densities of the fluid and structure are close a previous report p kuberry and h lee comput methods appl mech engrg 267 2013 pp 594 605 has suggested that recasting the fsi problem in the context of optimal control may significantly reduce computation time this paper introduces a neumann type control along with detailed analysis for the stability and existence of an optimal solution for a given time step the existence of lagrange multipliers is proved and an optimality system is derived a gradient based optimization algorithm is then presented with numerical results confirming its effectiveness in computing an accurate solution

an unfitted nitsche method for incompressible fluid structure interaction using overlapping meshes we consider the extension of the nitsche method to the case of fluid structure interaction problems on unfitted meshes we give a stability analysis for the space semi discretized problem and show how this estimate may be used to derive optimal error estimates for smooth solutions irrespectively of the mesh interface intersection we also discuss different strategies for the time discretization using either fully implicit or explicit coupling loosely coupled schemes some numerical examples illustrate the theoretical discussion

fluid structure interaction with large structural displacements the calculation of viscous flows inside deformable structures faces major difficulties when enforcing the kinematic compatibility at the fluid structure interface and updating the geometry of the domain this paper proposes to overcome these problems by considering the fluid and the structure as a unique continuous medium to be studied in a fixed reference configuration the resulting problem is then split into a fluid and a structural part through an additive decomposition of the space of kinematically admissible test functions this approach treats the structure in a fully lagrangian way and uses an associated arbitrary lagrangian eulerian ale formulation for the fluid such a strategy has three advantages which are detailed in the present paper it can be discretised in time by implicit stable energy conserving time integration schemes and solved by simple iterative uncoupled algorithms the fluid and the structural problems can be approximated by independent finite element spaces the most recent geometrically exact nonlinear shell models can be used for the structures the full strategy has been implemented into an industrial cfd code results obtained in the simulation of industrial hydraulic shock absorbers are presented at the end of the paper

controllability and control invariance in discrete event systems recently for discrete event systems modelled by automata ramadge and wonham 1987 a b have proposed two control techniques called supervisory control and state feedback logic if control specifications are given in terms of predicates on the set of states both techniques are applicable this paper discusses the relationship between these techniques it is shown that the language accepted by the discrete event system with maximally permissive feedback is equal to the supremal controllable language if the predicate is control invariant moreover it is shown that the predicate is control invariant if there exists a controllable language with a certain condition on the set of reachable states but the converse does not hold in general

truncation error and energy conservation for fluid structure interactions abstract this paper describes the numerical analysis of low speed large displacements fluid structure interaction problems after reviewing the basic conservation principles and kinematic interface conditions governing the problem under study it concentrates on truncation error and kinetic energy conservation such properties are indeed crucial for checking both the stability and convergence of the numerical scheme and the physical stability of the mechanical system under study we observe that classical time integration schemes which are dissipative unconditionally stable and accurate for fluids flowing inside fixed domains may loose their long term stability properties when used on moving domains we also produce new estimates proving that high order schemes using a partially nonconservative formulation associated to the variable j u properly conserve the kinetic energy and that the same schemes used on different formulations only conserve this energy approximately with an error which depends on the smoothness of the grid deformations and on the truncation error in the equation of mass conservation numerical results finally illustrate the approach

a high performance computing and sensitivity analysis algorithm for stochastic many particle wave scattering we present a high performance computing framework for quantifying uncertainties in the propagation of acoustic waves through a stochastic media comprising a large number of three dimensional particles we subsequently describe an efficient postprocessing approach using our framework to statistically quantify the sensitivity of the uncertainties with respect to input parameters that govern the stochasticity in the model the stochasticity arises through the random positions and orientations of the component particles in the media simulation even for a single deterministic three dimensional configuration is inherently difficult because of the large number of particles the stochasticity leads to a larger dimensional model involving three spatial variables and additional stochastic variables and accounting for uncertainty in key parameters of the input probability distributions leads to prohibitive computational complexity in the first part of our paper we describe a high performance computing framework f

a discontinuous stabilized mortar method for general 3d elastic problems first the present paper is concerned with the extension to linearized elastodynamics of the optimal results known in statics for the mortar method it also analyzes and tests a new couple of displacements lagrange multipliers for the method as proposed independently by ben belgacem f ben belgacem a stabilized domain decomposition method with non matching grids for the stokes problem in three dimensions siam j numer anal 42 2 2004 667 685 and the authors p hauret methodes numeriques pour la dynamique des structures non lineaires incompressibles a deux echelles numerical methods for the dynamic analysis of two scale incompressible nonlinear structures ph d thesis ecole polytechnique 2004 finally questions of practical implementation in the presence of curved interfaces are addressed and validated from the numerical point of view

partitioned procedures for the transient solution of coupled aroelastic problems part i model problem theory and two dimensional application abstract in order to predict the dynamic response of a flexible structure in a fluid flow the equations of motion of the structure and the fluid must be solved simultaneously in this paper we present several partitioned procedures for time integrating this focus coupled problem and discuss their merits in terms of accuracy stability heterogeneous computing i o transfers subcycling and parallel processing all theoretical results are derived for a one dimensional piston model problem with a compressible flow because the complete three dimensional aeroelastic problem is difficult to analyze mathematically however the insight gained from the analysis of the coupled piston problem and the conclusions drawn from its numerical investigation are confirmed with the numerical simulation of the two dimensional transient aeroelastic response of a flexible panel in a transonic non linear euler flow regime

a decoupling algorithm for fluid structure interaction problems based on optimization abstract simulating fluid structure interactions is challenging due to the tight coupling between the fluid and solid substructures explicit and implicit decoupling methods often either fail or require relaxation when densities of the two materials are close in this paper a fluid structure interaction problem is formulated as a least squares problem where the jump in velocities of the two substructures is minimized by a neumann control enforcing the continuity of stress on the interface a decoupling optimization algorithm is discussed which requires few nonlinear solves at each time step and numerical results are presented

elasto acoustic and acoustic acoustic coupling on non matching grids flexible discretization techniques for the approximative solution of coupled wave propagation problems are investigated focussing on aero acoustic and elasto acoustic coupling in particular the advantages of using non matching grids are presented when one subregion has to be resolved by a substantially finer grid than the other subregion for the elasto acoustic coupling the problem formulation remains essentially the same as for the matching situation while for the aero acoustic coupling the formulation is enhanced with lagrange multipliers within the framework of mortar finite element methods several numerical examples are presented to demonstrate the flexibility and applicability of the approach copyright 2006 john wiley sons ltd

long time behavior of a coupled heat wave system arising in fluid structure interaction this paper is devoted to the analysis of the long time behavior of a coupled wave heat system in which a wave and a heat equation evolve in two bounded domains with natural transmission conditions at a common interface these conditions couple in particular the heat unknown with the velocity of the wave solution this model may be viewed as a simplified version of linearized models which arise in fluid structure interaction first we show the strong asymptotic stability of solutions to this system then based on the construction of ray like solutions by means of geometric optics expansions and a careful analysis of the transfer of energy at the interface we show the lack of uniform decay in general domains further we obtain a polynomial decay result for smooth solutions of the system under a suitable geometric assumption which guarantees that the heat domain envelopes the wave domain finally in the absence of geometric conditions we show a logarithmic decay result for the same system but with simplified transmission conditions at the interface we also analyze the difficulty there is to extend this result to the more natural transmission conditions

explicit constructions of quasi monte carlo rules for the numerical integration of high dimensional periodic functions in this paper we give explicit constructions of point sets in the s dimensional unit cube yielding quasi monte carlo algorithms which achieve the optimal rate of convergence of the worst case error for numerically integrating high dimensional periodic functions in the classical measure p alpha of the worst case error introduced by korobov the convergence for every even integer alpha ge 1 is of cal o n min alpha d log n s alpha 2 where d is a parameter of the construction which can be chosen arbitrarily large and n is the number of quadrature points this convergence rate is known to be the best possible up to some log n factors we prove the result for the deterministic and also a randomized setting the construction is based on a suitable extension of digital t m s nets over the finite field mathbb z b

generalized energy momentum method for non linear adaptive shell dynamics in the present study a generalization of the energy momentum method denoted by generalized energy momentum method applied to the non linear dynamics of shells will be developed within the framework of the generalized a method this algorithmic environment contains the unconditionally stable energy momentum method and its numerically damped version as well as the classical newmark and a methods as special cases in order to control the size of the time steps of the integration scheme with respect to accuracy and eaciency an adaptive time stepping procedure based on local a posteriori error estimation will be improved for non linear dynamical systems and applied to the proposed class of algorithms the spatial discretization is realized by an eight noded finite shell element of reissner mindlin type including an extensible shell director field permitting the application of three dimensional material laws the original formulation of this finite element will be developed for non linear dynamic analysis and adapted for the employment within the introduced energy conserving decaying time integration scheme 1999 elsevier science s a all rights reserved

godunov type method on non structured meshes for three dimensional moving boundary problems abstract this paper presents a numerical method for the computation of compressible flows in domains whose boundaries move in a well defined predictable manner the method uses the space time formulation by godunov while the discretization is conducted on non structured tetrahedral meshes using roe s approximate riemann solver an implicit time stepping and a muscl type interpolation the computation of the geometrical parameters required to take into account the movement of the boundaries is described examples including the calculation of the flow in the cylinder of an internal combustion engine illustrates the possibilities of the method

fully discrete error estimation for a quasi newtonian fluid structure interaction problem we consider an incompressible quasi newtonian fluid structure interaction fsi problem formulated in a monolithic framework where the matching conditions at the moving interface are satisfied the fully discretized fsi system is discussed with detailed analysis for the stability and error estimate as well as numerical experiments that confirm the theoretical results

on the supermal controllable sublanguage of a given language the concept of controllable language has been shown to play a basic role in the existence theory of supervisory controls for discrete event processes in this paper the supremal controllable sublanguage s of a given language l is characterized as the largest fixpoint of a monotone operator omega in the case where the languages involved are regular it is shown that the fixpoint s can be computed as the limit of the finite sequence k j given by k j 1 omega k j k 0 l an effective computational algorithm is developed and three examples are provided for illustration

mixed interpretation and extensions of the equivalent mass matrix approach for elastodynamics with contact the present paper highlights the idea that the mass redistribution technique introduced by khenous and co workers 2006 17 18 for elastodynamics with impact can be reinterpreted as a mixed formulation in displacements and velocities in which a special compatibility condition is enforced such a formulation opens the route to various extensions and to variational integrators for impact problems potentially with variational time adaption those ideas are exemplified in the design of such integrators and various mass redistribution schemes

quasi monte carlo finite element methods for a class of elliptic partial differential equations with random coefficients in this paper quasi monte carlo qmc methods are applied to a class of elliptic partial differential equations pdes with random coefficients where the random coefficient is parametrized by a co

a temporal logic approach to discrete event control for the safety canonical class this paper presents a temporal logic formulation of discrete event control which forms a new theoretical basis for control analysis and synthesis of a class of discrete event systems des based on the formulation a basic supervisory control theory is developed for a control objective specified by an invariance formula belonging to the safety canonical class of manna and pneuli using the safety canonical class as a basis the refinement and generalization of the existing basic predicate framework are demonstrated a simple example illustrates the formal axiomatic means to perform control theoretic analysis and synthesis under the new formulation

an analysis of a new stable partitioned algorithm for fsi problems part i incompressible flow and elastic solids stable partitioned algorithms for fluid structure interaction fsi problems are developed and analyzed in this two part paper part i describes an algorithm for incompressible flow coupled with compressible elastic solids while part ii discusses an algorithm for incompressible flow coupled with structural shells importantly these new added mass partitioned amp schemes are stable and retain full accuracy with no sub iterations per time step even in the presence of strong added mass effects e g for light solids the numerical approach described here for bulk compressible solids extends the scheme of banks et al 1 2 for inviscid compressible flow and uses robin mixed boundary conditions with the fluid and solid solvers at the interface the basic amp robin conditions involving a linear combination of velocity and stress are determined from the outgoing solid characteristic relation normal to the fluid solid interface combined with the matching conditions on the velocity and traction two alternative forms of the amp conditions are then derived depending on whether the fluid equations are advanced with a fractional step method or not the stability and accuracy of the amp algorithm is evaluated for linearized fsi model problems the full nonlinear case being left for future consideration a normal mode analysis is performed to show that the new amp algorithm is stable for any ratio of the solid and fluid densities including the case of very light solids when added mass effects are large in contrast it is shown that a traditional partitioned algorithm involving a dirichlet neumann coupling for the same fsi problem is formally unconditionally unstable for any ratio of densities exact traveling wave solutions are derived for the fsi model problems and these solutions are used to verify the stability and accuracy of the corresponding numerical results obtained from the amp algorithm for the cases of light medium and heavy solids