A SPLITTER PLATE FOR THE PREVENTION OF VORTEX SHEDDING BEHIND FINITE CIRCULAR CYLINDERS IN UNIFORM CROSS FLOW

1967 ◽  
Author(s):  
Dirse W. Sallet
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Splitter Plate ◽  
Circular Cylinders

Numerical simulations of steady flow past two cylinders in staggered arrangements

2015 ◽  
Vol 765 ◽  
pp. 114-149 ◽  
Author(s):  
Feifei Tong ◽  
Liang Cheng ◽  
Ming Zhao
Keyword(s):  
Steady Flow ◽  
Vortex Shedding ◽  
Numerical Study ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Velocity Signal ◽  
Flow Features ◽  
Flow Information ◽  
Lift Forces ◽  
Pitch Distance

AbstractThis paper presents a numerical study on steady flow around two identical circular cylinders of various arrangements at a low subcritical Reynolds number ($\mathit{Re}=10^{3}$). The ratio of centre-to-centre pitch distance ($P$) to the diameter of the cylinder ($D$) ranges from 1.5 to 4, and the alignment angle $({\it\alpha})$ between the two cylinders and the direction of the cross-flow varies from 0 to 90°. The detailed flow information obtained from direct numerical simulation allows a comprehensive interpretation of the underlying physics responsible for some interesting flow features observed around two staggered cylinders. Four distinct vortex shedding regimes are identified and it is demonstrated that accurate classification of vortex shedding regimes around two staggered cylinders should consider the combination of the flow visualization with the analyses of lift forces and velocity signal in the wake. It is revealed that the change in pressure distribution, as a result of different vortex shedding mechanisms, leads to a variety of characteristics of hydrodynamic forces on both cylinders, including negative drag force, attractive and repulsive lift forces. Two distinct vortex shedding frequencies are identified and are attributed to the space differences based on the flow structures observed in the wake of the cylinders. It is also found that the three-dimensionality of flow in the gap and the shared wake region is significantly weakened in almost two of the classified flow regimes; however, compared with the flow around a single cylinder, active wake interaction at large ${\it\alpha}$ does not clearly increase the three-dimensionality.

Appraisal of Universal Wake Numbers From Data for Roughened Circular Cylinders

1983 ◽  
Vol 105 (4) ◽  
pp. 464-468 ◽  
Author(s):  
G. Buresti
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Drag Coefficient ◽  
Vortex Shedding ◽  
Physical Interpretation ◽  
Potential Flow ◽  
Bluff Body ◽  
Cross Flow ◽  
Sufficient Accuracy ◽  
Circular Cylinders

An analysis was carried out to check whether certain existing universal wake numbers can characterize the cross-flow around roughened circular cylinders in transitional regimes. The results confirmed the soundness of the idea of the existence of a link between the drag coefficient of a bluff body, its pressure distribution, and the frequency of the shedding of vortices in its wake. In particular, Bearman’s number and Griffin’s number were shown to be able to describe this link with sufficient accuracy and to be a function of the Reynolds number based on the typical dimension of the surface roughness. A physical interpretation of Griffin’s number was also given which permits to link the drag force with the velocity of the potential flow at separation and the frequency of vortex shedding.

The Role of Axial Flow in Near Wake on the Cross-Flow Vibration of the Inclined Cable of Cable-Stayed Bridges

2010 ◽  
Author(s):  
Masaru Matsumoto
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Axial Flow ◽  
Splitter Plate ◽  
Near Wake ◽  
Karman Vortex ◽  
The Cross ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

Nowadays, the violent wind-induced vibration, including “rain-wind induced vibration” and “dry-galloping”, of stay-cables of cable-stayed bridges has become the most serious issue for bridge design. Up-to-date, the major factors for excitation of inclined cables have been clarified to be, for “rain-wind” induced vibration, the formation of “water-rivulet” on the particular position of upper cable surface, and, for “dry galloping”, the “axial flow” which flows in the near wake along cable-axis, and the effect of drag-force associated with Reynolds number, separately. However, the details of the effect of “axial flow” remain unsolved. Thus, this study aims to clarify the effect of axial flow in near wake on the aero-elastic vibration of inclined cables basing on various experiments. The mean velocity of axial flow was almost 60% of approaching wind velocity. Furthermore, the aerodynamic effect of the “axial flow” on cross-flow vibration of inclined cables is discussed in relation to the mitigation of Karman vortex shedding in near wake. Since the role of axial flow seems to be similar to the splitter plate installed in wake from the point of mitigation of Karman vortex shedding, to clarify the cross-flow response in relation to the mitigation of Karman vortex, the perforated ratio of the splitter plate was variously changed, then the similarity of effect of axial flow and the one of splitter plate was verified comparing their unsteady lift force-characteristics. In summary, it is shown that the axial flow on aerodynamic cross-flow vibration might excite like galloping similarly with the splitter plate by mitigation of Karman vortex.

On the Suppression of Vortex Shedding From Circular Cylinders Using Detached Short Splitter-Plates

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Behzad Ghadiri Dehkordi ◽  
Hamed Houri Jafari
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Splitter Plate ◽  
Circular Cylinders ◽  
Staggered Grid ◽  
Drag Forces ◽  
Splitter Plates ◽  
Parallel Arrangement ◽  
Lift And Drag ◽  
Good Agreement

Flow over a circular cylinder with detached short splitter-plates is numerically simulated in order to assess the suppression of periodic vortex shedding. A finite-volume solver based on the Cartesian-staggered grid is implemented, and the ghost-cell method in conjunction with Great-Source-Term technique is employed in order to enforce directly the no-slip condition on the cylinder boundary. The accuracy of the solver is validated by simulation of the flow around a single circular cylinder. The results are in good agreement with the experimental data reported in the literature. Finally, the flows over a circular cylinder with splitter-plate in its downstream (off and on the centerline) are computed in Re=40 as a nonvortex shedding case and in Re=100 and 150 as cases with vortex shedding effects. The same simulations are also performed for the case where dual splitter-plates are in a parallel arrangement embedded in the downstream of the cylinder. The optimum location of the splitter-plate to achieve maximum reduction in the lift and drag forces is determined.

Closely Spaced Circular Cylinders in Cross-Flow and a Universal Wake Number

2004 ◽  
Vol 126 (2) ◽  
pp. 245-249 ◽  
Author(s):  
David Sumner
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
Incidence Angle ◽  
Cross Flow ◽  
Base Pressure ◽  
Circular Cylinders ◽  
Bluff Bodies ◽  
Aerodynamic Forces ◽  
Single Vortex ◽  
Total Drag

To investigate the effectiveness of a universal wake number for groups of closely spaced bluff bodes, staggered cylinder configurations with center-to-center pitch ratios of P/D=1.125 and 1.25, and incidence angles from α=0 deg–90 deg, were tested in the subcritical Reynolds number regime. The aerodynamic forces, base pressure, and vortex shedding frequencies were measured for the upstream and downstream cylinders, and were found to be strongly dependent on the incidence angle and small changes in the flow pattern. The Griffin number was found to be an appropriate universal wake number for the closely spaced staggered cylinders, based on the total drag force acting on the two cylinders, and the average base pressure for the two cylinders. The results suggest that the single vortex wake of a pair of closely spaced staggered cylinders is broadly comparable to the wake of a solitary bluff body, and that the universal wake number concept can be extended to groups of closely spaced bluff bodies.

Flow Around a Surface-Mounted Finite Square Prism With a Splitter Plate

2014 ◽  
Author(s):  
Ayodele R. Ogunremi ◽  
David Sumner
Keyword(s):  
Vortex Shedding ◽  
Ground Plane ◽  
Splitter Plate ◽  
Force Balance ◽  
Circular Cylinders ◽  
Splitter Plates ◽  
Aspect Ratios ◽  
Square Prism ◽  
Finite Height ◽  
Four Square

The effect of a wake-mounted splitter plate on the flow around a surface-mounted finite-height square prism was investigated experimentally in a low-speed wind tunnel. Four square prisms of aspect ratios AR = 9, 7, 5 and 3 were tested at a Reynolds number of Re = 7.4×104. The relative thickness of the boundary layer on the ground plane was δ/D = 1.5 (where D is the side length of the prism). The splitter plates were mounted vertically from the ground plane on the wake centreline, with a negligible gap between the leading edge of the plate and rear of the prism. The splitter plate heights were always the same as the heights of prisms, while the splitter plate lengths were varied from L/D = 1 to 7. Measurements of the mean drag force were obtained with a force balance, and measurements of the vortex shedding frequency were obtained with a single-sensor hot-wire probe. Compared to previously published results for an “infinite” square prism, a splitter plate is less effective at drag reduction, but more effective at vortex shedding suppression, when used with a finite-height square prism. Significant reduction in drag was realized only for short prisms (of AR ≤ 5) when long splitter plates (of L/D ≥ 5) were used. In contrast, a splitter plate of length L/D = 3 was sufficient to suppress vortex shedding for all aspect ratios tested. Compared to previous results for finite-height circular cylinders, finite-height square prisms typically need longer splitter plates for vortex shedding suppression.

Investigation of the flow between a pair of circular cylinders in the flopping regime

1988 ◽  
Vol 196 ◽  
pp. 431-448 ◽  
Author(s):  
H. J. Kim ◽  
P. A. Durbin
Keyword(s):  
Steady State ◽  
Vortex Shedding ◽  
Time Scale ◽  
Periodic Oscillation ◽  
Shear Layers ◽  
Splitter Plate ◽  
Circular Cylinders ◽  
Acoustic Excitation ◽  
Mean Flow ◽  
Symmetric Flow

The wakes of a pair of circular cylinders are grossly unsteady when the cylinders are separated in a direction normal to the approaching flow by less than one cylinder diameter. The wakes flop randomly between two asymmetric states. The time-scale for the flopping is several orders of magnitude longer than the timescale of vortex shedding, and also several orders of magnitude longer than the timescale for instability of the separating shear layers. When a splitter plate is positioned suitably on the centreline of the cylinders, the flopping can be stopped and the flow made to assume either of the asymmetric states, or a symmetric steady state. For a range of plate positions a new, periodic oscillation occurs. Acoustic excitation can also destroy the flopping mean flow, replacing it by a symmetric flow.

Interference Between Two Stationary or Elastically Supported Rigid Circular Cylinders of Unequal Diameters in Tandem and Staggered Arrangements

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Shan Huang ◽  
Andy Sworn
Keyword(s):  
Drag Reduction ◽  
Vortex Shedding ◽  
Damping Ratio ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Test Results ◽  
Damping Parameter ◽  
Frequency Components ◽  
Elastically Supported

Analysis of model test results was carried out to investigate the hydrodynamic interaction between pairs of fixed or elastically supported rigid cylinders of dissimilar diameters in a water flume. The two cylinders are placed with one situated in the wake of the other. The spacing between the cylinders ranges from 1 to 15 times the larger cylinder diameter. The Reynolds numbers are within the subcritical range. For the vibrating cylinders which are free to oscillate in both the in-line and the cross-flow directions, the reduced velocity ranges from 1 to 13 and the low damping ratio of the test setup at 0.006 gives a combined mass-damping parameter of 0.02. For the fixed cylinders, the downstream cylinder experiences a drag reduction and it was found that this drag reduction also depends upon the diameter ratio. The lift on the fixed downstream cylinder has the frequency components derived from the upstream cylinder's vortex shedding as well as from its own vortex shedding, and the relative importance of the two sources is influenced by the spacing between the two cylinders. This is reflected in the downstream cylinder's vortex induced vibration (VIV) response which appears to be dependent upon the actual reduced velocities of both the cylinders.

Vortex-Excited Cross-Flow Vibrations of a Single Cylindrical Tube

1980 ◽  
Vol 102 (2) ◽  
pp. 158-166 ◽  
Author(s):  
O. M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Cylindrical Tube ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Resonant Response ◽  
Single Tube ◽  
Fluid Forces ◽  
Dynamic Forces

The cross-flow vibrations of a single tube are considered in this paper, for incident flows of air and water. Recent experimental measurements of the resonant response of and fluid dynamic forces on circular cylinders as a result of vortex shedding at subcritical Reynolds numbers are presented, and different approaches to measuring and characterizing the fluid forces are compared. Based upon these experiments, a mathematical model with which to describe the flow-induced excitation and reaction (damping) forces on a vibrating tube has been developed and is presented here. These results are applicable in general not only to the resonant, vortex-excited vibrations of flexibly mounted rigid tubes, but also to a flexible tube in air, water and other similar fluids.

Numerical Investigation of Flow and Heat Transfer around Two Semi-Circular Cylinders with a Splitter Plate

2011 ◽  
Vol 42 (7) ◽  
pp. 595-612
Author(s):  
Masome Heidary ◽  
Mousa Farhadi ◽  
Kurosh Sedighi ◽  
Mostafa Nourollahi
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Splitter Plate ◽  
Circular Cylinders ◽  
Flow And Heat Transfer
Sign in / Sign up

Export Citation Format

Share Document