Hydrodynamic Drag On Bottom-Mounted Smooth And Rough Cylinders In Periodic Flow
01 Jan 1980-
About: The article was published on 1980-01-01. It has received 27 citations till now. The article focuses on the topics: Parasitic drag & Drag coefficient.
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TL;DR: In this paper, the authors deal with the flow around a circular cylinder placed near a plane wall and exposed to an oscillatory flow and show that the flow pattern and the pressure distribution change significantly because of the close proximity of the boundary where the symmetry in the formation of vortices breaks down, and also the characteristic transverse vortex street observed for wall-free cylinders for 7 < KC < 13 disappears.
Abstract: This study deals with the flow around a circular cylinder placed near a plane wall and exposed to an oscillatory flow. The study comprises instantaneous pressure distribution measurements around the cylinder at high Reynolds numbers (mostly at Re ∼ 105) and a flow visualization study of vortex motions at relatively smaller Reynolds numbers (Re ∼ 103–104). The range of the gap-to-diameter ratio is from 0 to 2 for the pressure measurements and from 0 to 25 for the flow visualization experiments. The range of the Keulegan–Carpenter number KC is from 4 to 65 for the pressure measurements and from 0 to 60 for the flow visualization tests. The details of vortex motions around the cylinder are identified for specific values of the gap-to-diameter ratio and for the KC regimes known from research on wall-free cylinders. The findings of the flow visualization study are used to interpret the variations in pressure with time around the pipe. The results indicate that the flow pattern and the pressure distribution change significantly because of the close proximity of the boundary where the symmetry in the formation of vortices breaks down, and also the characteristic transverse vortex street observed for wall-free cylinders for 7 < KC < 13 disappears. The results further indicate that the vortex shedding persists for smaller and smaller values of the gap-to-diameter ratio, as KC is decreased. The Strouhal frequency increases with decreasing gap-to-diameter ratio. The increase in the Strouhal frequency with respect to its wall-free-cylinder value can be as much as 50% when the cylinder is placed very close to the wall with a gap-to-diameter ratio of O(0.1).
69 citations
42 citations
TL;DR: The hydrodynamic force model for pipelines presented in this paper includes flow history effects (wake effects) and time dependence in the force coefficients, which are necessary to obtain satisfactory agreement between model predictions and full scale field measurements of pipeline forces.
33 citations
TL;DR: In this paper, the authors proposed an extension of the Wake II type model, originally proposed for sinusoidal waves and currents, to the case of periodic or random waves, even with a superimposed current.
21 citations
TL;DR: In this article, the wake velocity correction is derived by using a closed-form solution to the linearized Navier-Stokes equations for oscillatory flow, which is achieved by assuming that the eddy viscosity in the wake is only time dependent and of a harmonic sinusoidal form.
18 citations