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Detached Eddy simulation of free-surface flow around a submerged submarine fairwater / Z. Ikram in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 6 (Juin 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 6 (Juin 2012) . - 12 p. Titre : Detached Eddy simulation of free-surface flow around a submerged submarine fairwater Type de document : texte imprimé Auteurs : Z. Ikram, Auteur ; E. J. Avital, Auteur ; J. J. R. Williams, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : DES;  immersed  boundary;  free-surface;  Reynolds  number;  submergence  depth Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The effects of reducing submergence depth around a submerged submarine fairwater without its associated appendages is numerically studied using detached eddy simulation. The submerged body is modeled using the ghost-cell immersed boundary method, while the free-surface is accounted for by using a moving mesh. The numerical simulations are performed at a Reynolds number of 11 × 106 for a submergence ratio in the range of 0.44–0.32 and for Froude numbers <1. This paper examines the effect of depth variation on the statistical and structural behavior of the flow around a fully submerged fairwater. The results include profiles of the time averaged velocity, turbulent intensities, turbulent kinetic energy spectra and budget. These have all shown that the major part of the turbulence is confined to the near wake region of the fairwater. Vortical structures are found to show no significant rise or interaction with the free-surface, while in the wake region, the results show that vorticity is present for over 50% of the total monitored period. Reducing the submergence depth is found to influence the tip vortex shedding. Additionally, time averaged forces, force variations, and shedding frequency are also examined. In all cases, the surface waves generated by the submerged fairwater are of a Kelvin kind. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000006 [...] [article] Detached Eddy simulation of free-surface flow around a submerged submarine fairwater [texte imprimé] / Z. Ikram, Auteur ; E. J. Avital, Auteur ; J. J. R. Williams, Auteur . - 2012 . - 12 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 6 (Juin 2012) . - 12 p. Mots-clés : DES;  immersed  boundary;  free-surface;  Reynolds  number;  submergence  depth Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The effects of reducing submergence depth around a submerged submarine fairwater without its associated appendages is numerically studied using detached eddy simulation. The submerged body is modeled using the ghost-cell immersed boundary method, while the free-surface is accounted for by using a moving mesh. The numerical simulations are performed at a Reynolds number of 11 × 106 for a submergence ratio in the range of 0.44–0.32 and for Froude numbers <1. This paper examines the effect of depth variation on the statistical and structural behavior of the flow around a fully submerged fairwater. The results include profiles of the time averaged velocity, turbulent intensities, turbulent kinetic energy spectra and budget. These have all shown that the major part of the turbulence is confined to the near wake region of the fairwater. Vortical structures are found to show no significant rise or interaction with the free-surface, while in the wake region, the results show that vorticity is present for over 50% of the total monitored period. Reducing the submergence depth is found to influence the tip vortex shedding. Additionally, time averaged forces, force variations, and shedding frequency are also examined. In all cases, the surface waves generated by the submerged fairwater are of a Kelvin kind. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000006 [...]

Large eddy simulation of flow past free surface piercing circular cylinders / G. Yu in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 10 (Octobre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 9 p. Titre : Large eddy simulation of flow past free surface piercing circular cylinders Type de document : texte imprimé Auteurs : G. Yu, Auteur ; E. J. Avital, Auteur ; J. J. Williams, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (Dynamics);  wakes;  cylinders;  water;  drag  (Fluid  dynamics);  vortices;  large  eddy  simulation;  Reynolds  number Résumé : Flows past a free surface piercing cylinder are studied numerically by large eddy simulation at Froude numbers up to FrD=3.0 and Reynolds numbers up to ReD=1×105. A two-phase volume of fluid technique is employed to simulate the air-water flow and a flux corrected transport algorithm for transport of the interface. The effect of the free surface on the vortex structure in the near wake is investigated in detail together with the loadings on the cylinder at various Reynolds and Froude numbers. The computational results show that the free surface inhibits the vortex generation in the near wake, and as a result, reduces the vorticity and vortex shedding. At higher Froude numbers, this effect is stronger and vortex structures exhibit a 3D feature. However, the free surface effect is attenuated as Reynolds number increases. The time-averaged drag force on the unit height of a cylinder is shown to vary along the cylinder and the variation depends largely on Froude number. For flows at ReD=2.7×104, a negative pressure zone is developed in both the air and water regions near the free surface leading to a significant increase of drag force on the cylinder in the vicinity of the free surface at about FrD=2.0. The mean value of the overall drag force on the cylinder increases with Reynolds number and decreases with Froude number but the reduction is very small for FrD=1.6–2.0. The dominant Strouhal number of the lift oscillation decreases with Reynolds number but increases with Froude number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...] [article] Large eddy simulation of flow past free surface piercing circular cylinders [texte imprimé] / G. Yu, Auteur ; E. J. Avital, Auteur ; J. J. Williams, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 9 p. Mots-clés : Flow  (Dynamics);  wakes;  cylinders;  water;  drag  (Fluid  dynamics);  vortices;  large  eddy  simulation;  Reynolds  number Résumé : Flows past a free surface piercing cylinder are studied numerically by large eddy simulation at Froude numbers up to FrD=3.0 and Reynolds numbers up to ReD=1×105. A two-phase volume of fluid technique is employed to simulate the air-water flow and a flux corrected transport algorithm for transport of the interface. The effect of the free surface on the vortex structure in the near wake is investigated in detail together with the loadings on the cylinder at various Reynolds and Froude numbers. The computational results show that the free surface inhibits the vortex generation in the near wake, and as a result, reduces the vorticity and vortex shedding. At higher Froude numbers, this effect is stronger and vortex structures exhibit a 3D feature. However, the free surface effect is attenuated as Reynolds number increases. The time-averaged drag force on the unit height of a cylinder is shown to vary along the cylinder and the variation depends largely on Froude number. For flows at ReD=2.7×104, a negative pressure zone is developed in both the air and water regions near the free surface leading to a significant increase of drag force on the cylinder in the vicinity of the free surface at about FrD=2.0. The mean value of the overall drag force on the cylinder increases with Reynolds number and decreases with Froude number but the reduction is very small for FrD=1.6–2.0. The dominant Strouhal number of the lift oscillation decreases with Reynolds number but increases with Froude number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...]