Hydrodynamic regimes and drag on horizontally pulled floating spheres
KAUST DepartmentHigh-Speed Fluids Imaging Laboratory
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
KAUST Grant NumberURF/1/3723-01-01
Permanent link to this recordhttp://hdl.handle.net/10754/671118
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AbstractWe use high-speed imaging to investigate the movement of a floating sphere pulled horizontally along a water surface. The model sphere is 10 cm in diameter and has half of the water density resulting in a half-submerged static sphere. By varying the pulling force, we investigate the flow dynamics in the subcritical Reynolds number range, of Re ≈ 2 × 104 to 2 × 105. We characterize three hydrodynamic regimes with the increase in the pulling force, to which we refer to as: low Froude number, Fr < 0.6, intermediate, 0.6 < Fr < 1.2 and high Froude number, Fr > 1.2 regimes. In the low Fr regime, the sphere moves with little disturbance of the water surface and the drag is close to half of the drag on a fully submerged sphere. In the intermediate Fr regime, a pronounced wave pattern is developed which together with the dipping of the sphere below the water level leads to an increase in the drag force. Based on a potential flow approximation for the downward force on the sphere moving along the surface, we derive a semiempirical relation for the sphere dipping as a function of the Froude number. Finally, in the high Fr regime, the sphere movement switches to a mode of periodic dipping below and surfacing above the water surface. The periodic vertical motion portrays a decrease in the average drag force
CitationKamoliddinov, F., Vakarelski, I. U., & Thoroddsen, S. T. (2021). Hydrodynamic regimes and drag on horizontally pulled floating spheres. Physics of Fluids, 33(9), 093308. doi:10.1063/5.0061768
SponsorsWe acknowledge an anonymous referee for suggesting the sphere dipping analogy with ships sinkage. The work was supported by the King Abdullah University of Science and Technology (KAUST) under Grant No. URF/1/3723-01-01.
JournalPhysics of Fluids
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