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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 04 Dec 2021 23:05:50 GMT2021-12-04T23:05:50ZFlow and air-entrainment around partially submerged vertical cylinders
http://hdl.handle.net/10985/17944
Flow and air-entrainment around partially submerged vertical cylinders
AGEORGES, Valentin; PEIXINHO, Jorge; PÉRRET, Gaële
In this study, a partially submerged vertical cylinder is moved at constant velocity through water, which is initially at rest. During the motion, the wake behind the cylinder induces free-surface deformation. Eleven cylinders, with diameters from D=1.4 to 16 cm, were tested under two different conditions: (i) constant immersed height h and (ii) constant h/D. The range of translation velocities and diameters are in the regime of turbulent wake with experiments carried out for 4500<Re<240000 and 0.2<Fr<2.4, where Re and Fr are the Reynolds and Froude numbers based on D. The focus here is on drag-force measurements and relatively strong free-surface deformation up to air-entrainment. Specifically, two modes of air-entraiment have been uncovered: (i) in the cavity along the cylinder wall and (ii) in the wake of the cylinder. A scaling for the critical velocity for air-entrainment in the cavity has been observed in agreement with a simple model. Furthermore, for Fr>1.2, the drag force varies linearly with Fr.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/179442019-01-01T00:00:00ZAGEORGES, ValentinPEIXINHO, JorgePÉRRET, GaëleIn this study, a partially submerged vertical cylinder is moved at constant velocity through water, which is initially at rest. During the motion, the wake behind the cylinder induces free-surface deformation. Eleven cylinders, with diameters from D=1.4 to 16 cm, were tested under two different conditions: (i) constant immersed height h and (ii) constant h/D. The range of translation velocities and diameters are in the regime of turbulent wake with experiments carried out for 4500<Re<240000 and 0.2<Fr<2.4, where Re and Fr are the Reynolds and Froude numbers based on D. The focus here is on drag-force measurements and relatively strong free-surface deformation up to air-entrainment. Specifically, two modes of air-entraiment have been uncovered: (i) in the cavity along the cylinder wall and (ii) in the wake of the cylinder. A scaling for the critical velocity for air-entrainment in the cavity has been observed in agreement with a simple model. Furthermore, for Fr>1.2, the drag force varies linearly with Fr.Experiments and Simulations of Free-Surface Flow behind a Finite Height Rigid Vertical Cylinder
http://hdl.handle.net/10985/21219
Experiments and Simulations of Free-Surface Flow behind a Finite Height Rigid Vertical Cylinder
AGEORGES, Valentin; PEIXINHO, Jorge; PERRET, Gaële; LARTIGUE, Ghislain; MOUREAU, Vincent
We present the results of a combined experimental and numerical study of the free-surface flow behind a finite height rigid vertical cylinder. The experiments measure the drag and the wake angle on cylinders of different diameters for a range of velocities corresponding to 30,000 <Re< 200,000 and 0.2<Fr<2 where the Reynolds and Froude numbers are based on the diameter. The three-dimensional large eddy simulations use a conservative level-set method for the air-water interface, thus predicting the pressure, the vorticity, the free-surface elevation and the onset of air entrainment. The deep flow looks like single phase turbulent flow past a cylinder, but close to the free-surface, the interaction between the wall, the free-surface and the flow is taking place, leading to a reduced cylinder drag and the appearance of V-shaped surface wave patterns. For large velocities, vortex shedding is suppressed in a layer region behind the cylinder below the free surface. The wave patterns mostly follow the capillary-gravity theory, which predicts the crest lines cusps. Interestingly, it also indicates the regions of strong elevation fluctuations and the location of air entrainment observed in the experiments. Overall, these new simulation results, drag, wake angle and onset of air entrainment, compare quantitatively with experiments.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/212192021-01-01T00:00:00ZAGEORGES, ValentinPEIXINHO, JorgePERRET, GaëleLARTIGUE, GhislainMOUREAU, VincentWe present the results of a combined experimental and numerical study of the free-surface flow behind a finite height rigid vertical cylinder. The experiments measure the drag and the wake angle on cylinders of different diameters for a range of velocities corresponding to 30,000 <Re< 200,000 and 0.2<Fr<2 where the Reynolds and Froude numbers are based on the diameter. The three-dimensional large eddy simulations use a conservative level-set method for the air-water interface, thus predicting the pressure, the vorticity, the free-surface elevation and the onset of air entrainment. The deep flow looks like single phase turbulent flow past a cylinder, but close to the free-surface, the interaction between the wall, the free-surface and the flow is taking place, leading to a reduced cylinder drag and the appearance of V-shaped surface wave patterns. For large velocities, vortex shedding is suppressed in a layer region behind the cylinder below the free surface. The wave patterns mostly follow the capillary-gravity theory, which predicts the crest lines cusps. Interestingly, it also indicates the regions of strong elevation fluctuations and the location of air entrainment observed in the experiments. Overall, these new simulation results, drag, wake angle and onset of air entrainment, compare quantitatively with experiments.