Oscillatory flow over a cylinder resting on a plane boundary

1996 ◽  
Vol 7 (6) ◽  
pp. 545-558 ◽  
Author(s):  
M. F. Wybrow ◽  
N. Riley
Keyword(s):  
Circular Cylinder ◽  
Boundary Layers ◽  
Outer Layer ◽  
Oscillatory Flow ◽  
Outer Boundary ◽  
Reynolds Numbers ◽  
Plane Boundary ◽  
Simple Experiment ◽  
Steady Streaming ◽  
Streaming Motion

Oscillatory flow over a circular cylinder, or part-cylinder, placed on a plane boundary, when the Strouhal and streaming Reynolds numbers are large, is considered. The solution is developed in matching inner and outer boundary layers. A steady streaming motion in the outer layer can lead to a net flow away from the cylinder along the plane boundary. A simple experiment substantiates this prediction, and the implications for bed-scouring are examined.

Effect of a plane boundary on oscillatory flow around a circular cylinder

1991 ◽  
Vol 225 ◽  
pp. 271-300 ◽  
Author(s):  
B. M. Sumer ◽  
B. L. Jensen ◽  
J. Fredsøe
Keyword(s):  
Circular Cylinder ◽  
Flow Visualization ◽  
Pressure Distribution ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Plane Boundary ◽  
Pressure Measurements ◽  
Visualization Experiments ◽  
High Reynolds

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).

Unsteady flow about a sphere at low to moderate Reynolds number. Part 1. Oscillatory motion

1994 ◽  
Vol 277 ◽  
pp. 347-379 ◽  
Author(s):  
Eugene J. Chang ◽  
Martin R. Maxey
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Oscillatory Motion ◽  
Rigid Sphere ◽  
Flow Conditions ◽  
Steady Streaming ◽  
Moderate Reynolds Number

A direct numerical simulation, based on spectral methods, has been used to compute the time-dependent, axisymmetric viscous flow past a rigid sphere. An investigation has been made for oscillatory flow about a zero mean for different Reynolds numbers and frequencies. The simulation has been verified for steady flow conditions, and for unsteady flow there is excellent agreement with Stokes flow theory at very low Reynolds numbers. At moderate Reynolds numbers, around 20, there is good general agreement with available experimental data for oscillatory motion. Under steady flow conditions no separation occurs at Reynolds number below 20; however in an oscillatory flow a separation bubble forms on the decelerating portion of each cycle at Reynolds numbers well below this. As the flow accelerates again the bubble detaches and decays, while the formation of a new bubble is inhibited till the flow again decelerates. Steady streaming, observed for high frequencies, is also observed at low frequencies due to the flow separation. The contribution of the pressure to the resultant force on the sphere includes a component that is well described by the usual added-mass term even when there is separation. In a companion paper the flow characteristics for constant acceleration or deceleration are reported.

Coastal Bottom Boundary Layers

1995 ◽  
Vol 48 (9) ◽  
pp. 589-600 ◽  
Author(s):  
J. F. A. Sleath
Keyword(s):  
Steady Flow ◽  
Boundary Layers ◽  
Outer Layer ◽  
Oscillatory Flow ◽  
Shear Velocity ◽  
Grid Turbulence ◽  
Steady Flows ◽  
Turbulence Transition ◽  
Bottom Boundary Layers ◽  
Rough Beds

Turbulent boundary layers in oscillatory flow are reviewed. These boundary layers show a thin inner layer with similar characteristics to wall layers in steady flow. Above this, there is an outer layer which has some characteristics which are the same as those of steady flow outer layers and other characteristics which are different. One difference is that the defect velocity profile does not scale on the shear velocity alone. Also, over rough beds, the turbulence intensity in the outer layer falls off with height in a similar way to oscillating grid turbulence. Transition from laminar to turbulent flow is also reviewed. Combined oscillatory and steady flows are only briefly touched on.

Steady streaming around a circular cylinder in an oscillatory flow

2009 ◽  
Vol 36 (14) ◽  
pp. 1089-1097 ◽  
Author(s):  
Hongwei An ◽  
Liang Cheng ◽  
Ming Zhao
Keyword(s):  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Steady Streaming

Oscillatory flow over a circular cylinder close to a plane boundary

1996 ◽  
Vol 18 (5) ◽  
pp. 269-288 ◽  
Author(s):  
M F Wybrow ◽  
B Yan ◽  
N Riley
Keyword(s):  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Plane Boundary

Boundary-layer flow around a submerged circular cylinder induced by free-surface travelling waves

1996 ◽  
Vol 316 ◽  
pp. 241-257 ◽  
Author(s):  
B. Yan ◽  
N. Riley
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Wave Amplitude ◽  
Perturbation Methods ◽  
Travelling Waves ◽  
Inviscid Flow ◽  
Steady Streaming ◽  
Viscous Forces ◽  
Layer Flow ◽  
Streaming Motion

We consider the fluid flow induced when free-surface travelling waves pass over a submerged circular cylinder. The wave amplitude is assumed to be small, and a suitably defined Reynolds number large, so that perturbation methods may be employed. Particular attention is focused on the steady streaming motion, which induces circulation about the cylinder. The viscous forces acting on the cylinder are calculated and compared with the pressure forces which are solely responsible for the loading on the cylinder in a purely inviscid flow.

Planar Oscillatory Flow Forces at High Reynolds Numbers

1993 ◽  
Vol 115 (1) ◽  
pp. 31-39 ◽  
Author(s):  
J. R. Chaplin
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Number Range ◽  
High Reynolds Numbers ◽  
Reynolds Number Range ◽  
Fine Surface ◽  
High Reynolds

Measurements of pressures around a circular cylinder with fine surface roughness in planar oscillatory flow reveal considerable changes in drag and inertia coefficients over the Reynolds number range 2.5 × 105 to 7.5 × 105, and at Keulegan-Carpenter numbers between 5 and 25. In most respects, these results are shown to be compatible with previous measurements in planar oscillatory flow, and with previous measurements in which the same 0.5-m-dia cylinder was tested in waves.

scholarly journals Steady streaming around a cylinder pair

2016 ◽  
Vol 472 (2195) ◽  
pp. 20160522 ◽  
Author(s):  
W. Coenen
Keyword(s):  
Reynolds Number ◽  
Oscillatory Flow ◽  
Circular Cylinders ◽  
Flow Topology ◽  
Order Unity ◽  
Steady Streaming ◽  
Stokes Layer ◽  
Streaming Velocity ◽  
Gap Width ◽  
Streaming Motion

The steady streaming motion that appears around a pair of circular cylinders placed in a small-amplitude oscillatory flow is considered. Attention is focused on the case where the Stokes layer thickness at the surface of the cylinders is much smaller than the cylinder radius, and the streaming Reynolds number is of order unity or larger. In that case, the steady streaming velocity that persists at the edge of the Stokes layer can be imposed as a boundary condition to numerically solve the outer streaming motion that it drives in the bulk of the fluid. It is investigated how the gap width between the cylinders and the streaming Reynolds number affect the flow topology. The results are compared against experimental observations.

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