Potential Flow Past a Group of Circular Cylinders

1971 ◽  
Vol 93 (4) ◽  
pp. 636-642 ◽  
Author(s):  
C. Dalton ◽  
R. A. Helfinstine
Keyword(s):  
Potential Flow ◽  
Lift Coefficient ◽  
Controlling Factors ◽  
Circular Cylinders ◽  
Method Of Images ◽  
Single Cylinder ◽  
Flow Past ◽  
Inertial Coefficient

The problem of an accelerating potential flow past a group of stationary circular cylinders is considered using the method of images. The problem is formulated so that the number and location of the cylinders is arbitrary so long as there is no overlap between adjacent cylinders. Inertial and lift coefficients are determined for several different cylinder arrangements. The inertial coefficient for a cylinder can vary in either direction from its single-cylinder value of 2.0. The controlling factors on this variation are the relative geometric position of the cylinder within the group and its distance from its neighbors. These same factors determine, as is expected, the lift coefficient values. In two example configurations, there is even a drag-type force generated on an individual cylinder in the potential flow.

The predominant frequency for viscous flow past two tandem circular cylinders of different diameters at low Reynolds number

2019 ◽  
Vol 234 (2) ◽  
pp. 534-546
Author(s):  
Ming-ming Liu
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Viscous Flow ◽  
Lift Coefficient ◽  
Circular Cylinders ◽  
Predominant Frequency ◽  
Flow Past ◽  
Gap Ratio ◽  
The Mean ◽  
Different Diameters

Viscous flow past two circular cylinders in tandem arrangement is numerically investigated at a typical Reynolds number of 200 which is based on the diameter of the downstream cylinder. The non-dimensional diameter of the downstream cylinder D is fixed to be 1.0, while the non-dimensional diameter of the upstream cylinder d varies from 0.1 to 1.0 with an interval of 0.1. Moreover, the minimal non-dimensional distance between the two cylinders changes from 0.1 to 4.0. The numerical results show that continuous variation of the mean drag coefficient, the lift coefficient, and the lift frequency is observed with the increase in the gap ratio for d/ D = 0.1 and 0.2. Discontinuities are found for the mean drag coefficient, the lift coefficient, and the lift frequency of the downstream cylinder with the increase in gap ratio for d/ D = 0.9 and 1.0. Multiple lift oscillating frequencies of the downstream cylinder can be detected for d/ D = 0.3–0.8 at special gap ratios. Special attention is paid on d/ D = 0.4, which is a typical example for d/ D = 0.3–0.8. The predominant lift frequency of the downstream cylinder is observed to change from fL-1 to fL-2 as the increase in the gap ratio for d/ D = 0.4, which have not been previously detected. However, the predominant drag frequency of the downstream cylinder is found always to be fD-3 in present investigation scope. Moreover, a conclusion that fD-3 =  fL-1 +  fL-2 can be obtained.

Potential Flow Theory and Numerical Analysis of Forces on Cylinders Induced by Oscillating Disturbances

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Daniel T. Valentine ◽  
Farshad Madhi
Keyword(s):  
Unsteady Flow ◽  
Vortex Shedding ◽  
Potential Flow ◽  
Model Problem ◽  
Complete Solution ◽  
Boundary Integral ◽  
Circular Cylinders ◽  
Method Of Images ◽  
Surface Distribution ◽  
Flow Problems

The complete solution of several two-dimensional potential flow problems are reported that deal with the unsteady flow around circular cylinders. Three of the flows considered are induced by an oscillating disturbance near the cylinder. The three elemental disturbances examined are (1) a pulsating source, (2) a pulsating doublet, and (3) a pulsating vortex. The formulas for the force acting on the cylinder due to each of the elemental disturbances were derived by applying the method of images. These results were checked by deriving the equivalent surface distribution of sources to model the cylinder by applying Green’s second identity. The theory helped direct the development of a boundary-integral numerical model described and applied in this paper to solve the unsteady flow around a circular cylinder due to an arbitrarily specified oscillatory disturbance near the cylinder. The numerical method is validated by comparing predictions of the force with the exact solutions. We applied the theory to examine a model problem related to the vortex-shedding force that causes vortex-induced vibration.

scholarly journals Mixed convection flow past a horizontal plate

2005 ◽  
Vol 32 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Lj. Savic ◽  
H. Steinrück
Keyword(s):  
Mixed Convection ◽  
Small Angle ◽  
Potential Flow ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Large Reynolds Number ◽  
Convection Flow ◽  
Horizontal Plate ◽  
Mixed Convection Flow ◽  
Flow Past

The mixed convection flow past a horizontal plate being aligned through a small angle of attack to a uniform free stream will be considered in the limit of large Reynolds number and small Richardson number. Even a small angle of inclination of the wake is sufficient for the buoyancy force to accelerate the flow in the wake which causes a velocity overshoot in the wake. Moreover a hydrostatic pressure difference across the wake induces a correction to the potential flow which influences the inclination of the wake. Thus the wake and the correction of the potential flow have to be determined simultaneously. However, it turns out that solutions exist only if the angle of attack is sufficiently large. Solutions are computed numerically and the influence of the buoyancy on the lift coefficient is determined.

Steady incompressible flow past a row of circular cylinders

1991 ◽  
Vol 225 ◽  
pp. 655-671 ◽  
Author(s):  
Bengt Fornberg
Keyword(s):  
Reynolds Number ◽  
Incompressible Flow ◽  
Numerical Solutions ◽  
Major Change ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Single Cylinder ◽  
Flow Past

Numerical solutions are presented for steady two-dimensional incompressible flow past an infinite row of cylinders (of unit radii, with distances W between their centres). The calculations cover R [les ] 700 for 5 [les ] W [les ] ∞ and also R = 800 for 5 [les ] W [les ] 100 (where R denotes the Reynolds number based on the cylinder diameters). The recirculation regions (wake bubbles) are found to grow in length approximately linearly with R in all cases. For high values of R, a major change occurs in their character when W is increased past Wcrit ≈ 16. While they have remained slender up to this point (essentially only stretching in length in proportion to R), their centres of circulation have moved towards their ends. As W is further increased, the wake bubbles widen rapidly, beginning from the rear of the wakes. In the limit of W→∞, the present results agree with the previous ones for a single cylinder as reported by Fornberg (1985).

Numerical simulation of flow past two circular cylinders in cruciform arrangement

2018 ◽  
Vol 848 ◽  
pp. 1013-1039 ◽  
Author(s):  
Ming Zhao ◽  
Lin Lu
Keyword(s):  
Standard Deviation ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Circular Cylinders ◽  
Local Flow ◽  
Wake Vortices ◽  
Flow Past ◽  
The Mean

Flow past two circular cylinders in cruciform arrangement is simulated by direct numerical simulations for Reynolds numbers ranging from 100 to 500. The study is aimed at investigating the local flow pattern near the gap between the two cylinders, the global vortex shedding flow in the wake of the cylinders and their effects on the force coefficients of the two cylinders. The three identified local flow patterns near the gap: trail vortex (TV), necklace vortex (NV) and vortex shedding in the gap (SG) agree with those found by flow visualization in experimental studies. As for the global wake flow, two modes of vortex shedding are identified: K mode with inclined wake vortices and P mode where the wake vortices are parallel to the cylinders. The K mode occurs when the gap is slightly greater than the boundary gap between the NV and SG. It also coexists with the SG gap flow pattern if the Reynolds number is very small ($Re=100$). The flow pattern affects the force coefficient. The K mode increases the mean drag coefficient and the standard deviation of the lift coefficient at the centre of the upstream cylinder because the wake vortices converge towards the centre. The mean drag coefficient and standard deviation of the lift coefficient of the downstream cylinder decreases because of the shedding effect from the upstream cylinder.

Unsteady Potential Flow Theory and Numerical Analysis of Forces on Cylinders Induced by Nearby Oscillating Disturbances

2009 ◽  
Author(s):  
Daniel T. Valentine ◽  
Farshad Madhi
Keyword(s):  
Numerical Model ◽  
Unsteady Flow ◽  
Potential Flow ◽  
Complete Solution ◽  
Boundary Integral ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Method Of Images ◽  
Surface Distribution ◽  
Flow Problems

The complete solution of several two-dimensional potential flow problems are reported that deal with the unsteady flow around circular cylinders. Three of the flows considered are induced by an oscillating disturbance near the cylinder. The three elemental disturbances examined are (1) a pulsating source, (2) a pulsating doublet and (3) a pulsating vortex. The formulas for the force acting on the cylinder due to each of the elemental disturbances were derived by applying the method of images and checked by deriving the equivalent surface distribution of sources to model the cylinder starting with Green’s second identity. The theory helped direct the development of a boundary-integral numerical model described and applied in this paper to solve the unsteady flow around a circular cylinder due to an arbitrarily specified oscillatory disturbance near the cylinder. The numerical method is validated by comparing predictions of the force with the exact solutions.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

The supersonic and low-speed flows past circular cylinders of finite length supported at one end

1962 ◽  
Vol 12 (3) ◽  
pp. 367-387 ◽  
Author(s):  
D. M. Sykes
Keyword(s):  
Mach Number ◽  
Finite Length ◽  
Central Region ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Form Drag ◽  
Drag Coefficients ◽  
Low Speed ◽  
Flow Past ◽  
Length To Diameter Ratio

The flow past circular cylinders of finite length, supported at one end and lying with their axes perpendicular to a uniform stream, has been investigated in a supersonic stream at Mach number 1.96 and also in a low-speed stream. In both stream it was found that the flow past the cylinders could be divided into three regions: (a) a central region, (b) that near the free end of the cylinder, and (c) that near the supported end. The locations of the second and third regions were found to be almost independent of the cylinder length-to-diameter ratio, provided that this exceeded 4, while the flow within and the extent of the first region were dependent on this ratio. Form-drag coefficients determined in the central region in the supersonic flow were in close agreement with the values determined at the same Mach number by other workers. In the low-speed flow the local form-drag coefficients were dependent on length-to-diameter ratio and were always less than that of an infinite-length cylinder at the same Reynolds number.

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