Roger Lewandowski

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We consider the case of a homogeneous, isotropic, fully developed, turbulent flow. We show analytically by using the − 5/3 Kolmogorov's law that the time averaged consistency error of the N th approximate deconvolution LES model converges to zero following a law as the cube root of the averaging radius, independently of the Reynolds number. The consistancy(More)
In averaging the Navier-Stokes equations the problem of closure arises. Scale similarity models address closure by (roughly speaking) extrapolation from the (known) resolved scales to the (unknown) unresolved scales. In a posteriori tests scale similarity models are often the most accurate but can prove to be unstable when used in a numerical simulation. In(More)
In 1934 J. Leray proposed a regularization of the Navier-Stokes equations whose limits were weak solutions of the NSE. Recently, a modification of the Leray model, called the Leray-alpha model, has atracted study for turbulent flow simulation. One common drawback of Leray type regularizations is their low accuracy. Increasing the accuracy of a simulation(More)
On introduit uné equation de déconvolution qui généralise l'algorithme de Van-Cittert pour des conditions aux limites de type océananique avec vent fixé. On en déduit un modèle de SGE pour lequel on a existence et unicité d'une solutionrégulì ere. Nous détaillons un ensemble de simulations numériques qui montrent l'intérêt pratique du modèle. Abstract We(More)
This paper is devoted to the simulation of the flow around and inside a rigid axisym-metric net. We describe first how experimental data have been obtained. We show in detail the modelization. The model is based on a Reynolds Averaged Navier-Stokes turbulence model penalized by a term based on the Brinkman law. At the out-boundary of the computational box,(More)
Button or disc batteries have become increasingly popular as the energy source for electronic devices such as cameras, calculators, computers, watches, hearing aids and children's toys. Button battery burns to the gastrointestinal tract, ear and nose have been reported in children from many centres. Cutaneous injury from these sources has not been similarly(More)
We consider a system of equations that models the stationary flow of two im-miscible turbulent fluids on adjacent subdomains. The equations are coupled by nonlinear boundary conditions on the interface which is here a fixed given surface. We propose a spectral discretization of this problem and perform its numerical analysis. The convergence of the method(More)