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Local large scale forcing of unsheared turbulence

Bodart, Julien and Joly, Laurent and Cazalbou, Jean-Bernard Local large scale forcing of unsheared turbulence. ( In Press: 2008) In: Direct and Large Eddy Simulation 7, 08-10 Sept 2008, Trieste, Italy .

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Official URL: http://www2.units.it/~dles7/

Abstract

With the objective of studying the interaction between turbulence and a solid wall, a new way to generate a statistically steady turbulent state in a DNS setup is presented. Computation of ideal situations like turbulence diffusing from a plane/point source requires to impleme nt mechanisms of turbulent production that, (i) do not rely on the presence of mean-velocity gradients and, (ii) can be localized in space. A first way to devise a shear-free turbulence-production mechanism has been proposed by Alvelius, it was based on the use of a random force field, defined in the spectral space and, consequently, not localized in the physical space. This method has been modified by Campagne in order to confine the force field in a finite-width, plane layer of fluid and study the interaction between unsheared turbulence and a free-slip surface. Since the Navier-Stokes solver was based on a pseudo-spectral method, the method of Alvelius was both a convenient and natural choice. In order to extend the work of Campagne to the case of the interaction with a solid wall, we developed a mixed spectral/finite-difference Navier-Stokes solver. In this context, it is appealing to implement the forcing mechanism in the physical space. Such forcing methods have been recently proposed by Rosales & Meneveau and Nagata. In the first study the random force field is linear (proportional to the instantaneous velocity field) while the second study makes use of randomly-distributed elementary force fields (blobs). In either case, the forcing is statistically homogeneous in all the computational domain. In this paper, we present results obtained with a forcing method which is rather similar to that of Nagata. However, we use a different kind of elementary force patterns, and confine the forcing inside a plane layer of fluid. The latter characteristic relies on the use of compact supports for the force patterns.

Item Type:Conference or Workshop Item (Paper)
Audience (conference):International conference proceedings
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Institution: Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE
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Deposited By: Julien Bodart

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