Dynamics of coherent vortices in mixing layers using direct numerical and large-eddy simulations



Título del documento: Dynamics of coherent vortices in mixing layers using direct numerical and large-eddy simulations
Revista: Journal of the Brazilian Society of Mechanical Sciences
Base de datos: PERIÓDICA
Número de sistema: 000312030
ISSN: 0100-7386
Autores: 1
Instituciones: 1Universidade Federal do Rio Grande do Sul, Departamento de Matematica Pura e Aplicada, Porto Alegre, Rio Grande do Sul. Brasil
Año:
Volumen: 22
Número: 1
Paginación: 53-67
País: Brasil
Idioma: Inglés
Tipo de documento: Artículo
Enfoque: Analítico
Resumen en inglés Coherent vortices in turbulent mixing layers are investigated by means of Direct Numerical Simulation (DNS) and Large-Eddy Simulation (LES). Subgrid-scale models defined in spectral and physical spaces are reviewed. The new "spectral-dynamic viscosity model", that allows to account for non-developed turbulence in the subgrid-scales, is discussed. Pseudo-spectral methods, combined with sixth-order compact finite differences schemes (when periodic boundary conditions cannot be established), are used to solve the Navier- Stokes equations. Simulations in temporal and spatial mixing layers show two types of pairing of primary Kelvin-Helmholtz (KH) vortices depending on initial conditions (or upstream conditions): quasi-2D and helical pairings. In both cases, secondary streamwise vortices are stretched in between the KH vortices at an angle of 45° with the horizontal plane. These streamwise vortices are not only identified in the early transitional stage of the mixing layer but also in self-similar turbulence conditions. The Re dependence of the "diameter" of these vortices is analyzed. Results obtained in spatial growing mixing layers show some evidences of pairing of secondary vortices; after a pairing of the primary Kelvin-Helmholtz (KH) vortices, the streamwise vortices are less numerous and their diameter has increased than before the pairing of KH vortices
Disciplinas: Física y astronomía,
Ciencias de la computación
Palabras clave: Dinámica de fluidos,
Vórtices coherentes,
Capa de mezcla,
Simulación numérica,
Simulación Large Eddy,
Subredes
Keyword: Physics and astronomy,
Computer science,
Fluid dynamics,
Coherent vortices,
Mixing layers,
Numerical simulation,
Large Eddy simulation,
Subgrids
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