Documents disponibles écrits par cet auteur

Identification of flow structures on a LP turbine blade due to periodic passing wakes / S. Sarkar in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 6 (Juin 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 6 (Juin 2008) . - 10 p. Titre : Identification of flow structures on a LP turbine blade due to periodic passing wakes Type de document : texte imprimé Auteurs : S. Sarkar, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  structures;  low-pressure  turbine Résumé : The paper describes the flow structures on the suction surface of a highly cambered low-pressure turbine (LPT) blade (T106 profile) subjected to periodic convective wakes. A separation bubble on the rear half of the suction side of the blade was found to form under the operating condition due to the highly diffusive boundary layer. Interactions of migrating wakes with this separated boundary layer trigger rollup of the shear layer leading to transition and the appearance of coherent vortices. To characterize the dynamics of these large-scale structures, a proper orthogonal decomposition is pursued on both the fluctuating velocity and the vorticity fields generated by large-eddy simulations (LESs) of wake passing over the LPT blade for a Reynolds number Re=1.6×105. The first two modes clearly depict the rollup of the unstable shear layer and formation of large-scale vortex loops that contain a major fraction of the fluctuation energy. The present LES, at least in a qualitative sense, illustrates the large-scale motions in the outer layer and dynamics of vortical structures in a separated boundary layer excited by external perturbations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27318 [...] [article] Identification of flow structures on a LP turbine blade due to periodic passing wakes [texte imprimé] / S. Sarkar, Auteur . - 2009 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 6 (Juin 2008) . - 10 p. Mots-clés : Flow  structures;  low-pressure  turbine Résumé : The paper describes the flow structures on the suction surface of a highly cambered low-pressure turbine (LPT) blade (T106 profile) subjected to periodic convective wakes. A separation bubble on the rear half of the suction side of the blade was found to form under the operating condition due to the highly diffusive boundary layer. Interactions of migrating wakes with this separated boundary layer trigger rollup of the shear layer leading to transition and the appearance of coherent vortices. To characterize the dynamics of these large-scale structures, a proper orthogonal decomposition is pursued on both the fluctuating velocity and the vorticity fields generated by large-eddy simulations (LESs) of wake passing over the LPT blade for a Reynolds number Re=1.6×105. The first two modes clearly depict the rollup of the unstable shear layer and formation of large-scale vortex loops that contain a major fraction of the fluctuation energy. The present LES, at least in a qualitative sense, illustrates the large-scale motions in the outer layer and dynamics of vortical structures in a separated boundary layer excited by external perturbations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27318 [...]

Large-eddy simulation of wake and boundary layer interactions behind a circular cylinder / S. Sarkar in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 9 (Septembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 13 p. Titre : Large-eddy simulation of wake and boundary layer interactions behind a circular cylinder Type de document : texte imprimé Auteurs : S. Sarkar, Auteur ; Sudipto Sarkar, Auteur Année de publication : 2009 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : circular  cylinder;  large-Eddy  simulation Résumé : Large-eddy simulations (LESs) of flow past a circular cylinder in the vicinity of a flat plate have been carried out for three different gap-to-diameter (G/D) ratios of 0.25, 0.5, and 1.0 (where G signifies the gap between the flat plate and the cylinder, and D signifies the cylinder diameter) following the experiment of (2002, “Flow Visualization Around a Circular Cylinder Near to a Plane Wall,” J. Fluids Struct., 16, pp. 175–191). The flow visualization along with turbulent statistics are presented for a Reynolds number of Re=1440 (based on D and the inlet free-stream velocity U∞). The three-dimensional time-dependent, incompressible Navier–Stokes equations are solved using a symmetry-preserving finite-difference scheme of second-order spatial and temporal accuracy. The immersed-boundary method is employed to impose the no-slip boundary condition at the cylinder surface. An attempt is made to understand the physics of flow involving interactions of shear layers shed from the cylinder and the wall boundary layer. Present LES reveals the shear layer instability and formation of small-scale eddies apart from their mutual interactions with the boundary layer. It has been observed that G/D ratio has a large influence on the modification of wake dynamics and evolution of the wall boundary layer. For a low gap ratio, it is difficult to identify the boundary layer because of its strong interactions with the shear layers; however, a rapid transition to turbulence of the boundary layer, which is similar to bypass transition, is observed for a large gap ratio. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Large-eddy simulation of wake and boundary layer interactions behind a circular cylinder [texte imprimé] / S. Sarkar, Auteur ; Sudipto Sarkar, Auteur . - 2009 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 13 p. Mots-clés : circular  cylinder;  large-Eddy  simulation Résumé : Large-eddy simulations (LESs) of flow past a circular cylinder in the vicinity of a flat plate have been carried out for three different gap-to-diameter (G/D) ratios of 0.25, 0.5, and 1.0 (where G signifies the gap between the flat plate and the cylinder, and D signifies the cylinder diameter) following the experiment of (2002, “Flow Visualization Around a Circular Cylinder Near to a Plane Wall,” J. Fluids Struct., 16, pp. 175–191). The flow visualization along with turbulent statistics are presented for a Reynolds number of Re=1440 (based on D and the inlet free-stream velocity U∞). The three-dimensional time-dependent, incompressible Navier–Stokes equations are solved using a symmetry-preserving finite-difference scheme of second-order spatial and temporal accuracy. The immersed-boundary method is employed to impose the no-slip boundary condition at the cylinder surface. An attempt is made to understand the physics of flow involving interactions of shear layers shed from the cylinder and the wall boundary layer. Present LES reveals the shear layer instability and formation of small-scale eddies apart from their mutual interactions with the boundary layer. It has been observed that G/D ratio has a large influence on the modification of wake dynamics and evolution of the wall boundary layer. For a low gap ratio, it is difficult to identify the boundary layer because of its strong interactions with the shear layers; however, a rapid transition to turbulence of the boundary layer, which is similar to bypass transition, is observed for a large gap ratio. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]