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http://dspace.mediu.edu.my:8181/xmlui/handle/123456789/4549| Title: | Dynamics of coherent vortices in mixing layers using direct numerical and large-eddy simulations |
| Keywords: | Coherent Vortices Mixing Layer Direct Numerical Simulation Large-Eddy Simulation Subgrid Scales Models |
| Issue Date: | 30-May-2013 |
| Publisher: | The Brazilian Society of Mechanical Sciences |
| Description: | 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. |
| URI: | http://koha.mediu.edu.my:8181/jspui/handle/123456789/4549 |
| Other Identifiers: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-73862000000100005 http://www.doaj.org/doaj?func=openurl&genre=article&issn=01007386&date=2000&volume=22&issue=1&spage=53 |
| Appears in Collections: | Technology and Engineering |
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