Low Reynolds Flow Past a Circular Cylinder Close to a Free-Surface With Vertical Motion Dynamics

2016 ◽  
Author(s):  
Jose L. Cercos-Pita ◽  
Andrea Colagrossi ◽  
Antonio Souto-Iglesias
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Flow Characteristics ◽  
Vertical Motion ◽  
Bluff Bodies ◽  
Flow Past ◽  
Low Reynolds ◽  
Work Done ◽  
Large Response

Flow past a circular cylinder close to a free surface at low Reynolds number is investigated numerically in this paper extending the work done in previous 2014 and 2015 OMAE papers [1, 2]. In the former, the dependence of the flow with the submergence was discussed and in the latter the flow at high Froude numbers was investigated. It was found that shedding is blocked as the cylinder approaches de free surface with an increasing value of the net lift coefficient and a reduction of the lift alternate oscillations due to such shedding. This variation on the lift pattern suggests that if a VIVACE device [3] is set under these flow characteristics, its performance will significantly differ from that in deep water conditions. These devices take advantage of flow induced motions in bluff bodies (such as the cylinder) to generate electric power. Singh & Mittal [4] coupled VIV system is studied in present paper in the presence of a free surface, selecting a configuration with large response in unbounded flow and adding a free-surface to such case. Results are presented and discussed.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

Steady approach of unsteady low-Reynolds-number flow past two rotating circular cylinders

2013 ◽  
Vol 736 ◽  
pp. 414-443 ◽  
Author(s):  
Y. Ueda ◽  
T. Kida ◽  
M. Iguchi
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Stokes Equations ◽  
Low Reynolds Number ◽  
Vortex Method ◽  
The Self ◽  
Circular Cylinders ◽  
Far Field ◽  
Flow Past ◽  
Low Reynolds

AbstractThe long-time viscous flow about two identical rotating circular cylinders in a side-by-side arrangement is investigated using an adaptive numerical scheme based on the vortex method. The Stokes solution of the steady flow about the two-cylinder cluster produces a uniform stream in the far field, which is the so-called Jeffery’s paradox. The present work first addresses the validation of the vortex method for a low-Reynolds-number computation. The unsteady flow past an abruptly started purely rotating circular cylinder is therefore computed and compared with an exact solution to the Navier–Stokes equations. The steady state is then found to be obtained for $t\gg 1$ with ${\mathit{Re}}_{\omega } {r}^{2} \ll t$, where the characteristic length and velocity are respectively normalized with the radius ${a}_{1} $ of the circular cylinder and the circumferential velocity ${\Omega }_{1} {a}_{1} $. Then, the influence of the Reynolds number ${\mathit{Re}}_{\omega } = { a}_{1}^{2} {\Omega }_{1} / \nu $ about the two-cylinder cluster is investigated in the range $0. 125\leqslant {\mathit{Re}}_{\omega } \leqslant 40$. The convection influence forms a pair of circulations (called self-induced closed streamlines) ahead of the cylinders to alter the symmetry of the streamline whereas the low-Reynolds-number computation (${\mathit{Re}}_{\omega } = 0. 125$) reaches the steady regime in a proper inner domain. The self-induced closed streamline is formed at far field due to the boundary condition being zero at infinity. When the two-cylinder cluster is immersed in a uniform flow, which is equivalent to Jeffery’s solution, the streamline behaves like excellent Jeffery’s flow at ${\mathit{Re}}_{\omega } = 1. 25$ (although the drag force is almost zero). On the other hand, the influence of the gap spacing between the cylinders is also investigated and it is shown that there are two kinds of flow regimes including Jeffery’s flow. At a proper distance from the cylinders, the self-induced far-field velocity, which is almost equivalent to Jeffery’s solution, is successfully observed in a two-cylinder arrangement.

scholarly journals Effect of Cylinder Gap Ratio on The Wake of a Circular Cylinder Enclosed by Various Perforated Shrouds

CFD letters ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 51-68
Author(s):  
Nurul Azihan Ramli ◽  
Azlin Mohd Azmi ◽  
Ahmad Hussein Abdul Hamid ◽  
Zainal Abidin Kamarul Baharin ◽  
Tongming Zhou
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Control Method ◽  
Lift Coefficient ◽  
Base Case ◽  
Bluff Bodies ◽  
Ansys Fluent ◽  
Gap Ratio ◽  
Spacing Ratio

Flow over bluff bodies produces vortex shedding in their wake regions, leading to structural failure from the flow-induced forces. In this study, a passive flow control method was explored to suppress the vortex shedding from a circular cylinder that causes many problems in engineering applications. Perforated shrouds were used to control the vortex shedding of a circular cylinder at Reynolds number, Re = 200. The shrouds were of non-uniform and uniform holes with 67% porosity. The spacing gap ratio between the shroud and the cylinder was set at 1.2, 1.5, 2, and 2.2. The analysis was conducted using ANSYS Fluent using a viscous laminar model. The outcomes of the simulation of the base case were validated with existing studies. The drag coefficient, Cd, lift coefficient, Cl and the Strouhal number, St, as well as vorticity contours, velocity contours, and pressure contours were examined. Vortex shedding behind the shrouded cylinders was observed to be suppressed and delayed farther downstream with increasing gap ratio. The effect was significant for spacing ratio greater than 2.0. The effect of hole types: uniform and non-uniform holes, was also effective at these spacing ratios for the chosen Reynolds number of 200. Specifically, a spacing ratio of 1.2 enhanced further the vortex intensity and should be avoided.

Laminar Flow Past a Circular Cylinder: Reduction of Drag and Fluctuating Lift Using Upstream and Downstream Rods

2014 ◽  
Vol 493 ◽  
pp. 9-14
Author(s):  
Dedy Zulhidayat Noor ◽  
Eddy Widiyono ◽  
Suhariyanto ◽  
Lisa Rusdiyana ◽  
Joko Sarsetiyanto
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Passive Control ◽  
Low Reynolds Number ◽  
Tandem Arrangement ◽  
Single Cylinder ◽  
Flow Past ◽  
Low Reynolds

Laminar flow past a circular cylinder has been studied numerically at low Reynolds number. The upstream and downstream rods have been used as passive control in order to reduce hydrodynamics forces acting on the cylinder. Both the upstream and downstream rods significantly contribute in reduction of drag and fluctuating lift compared to single cylinder without the rods. More detail, the upstream installation rod is more dominant in drag reduction than the downstream one. On the contrary, the downstream rod has suppressed the magnitude of the fluctuating lift almost twice that of the upstream configuration. Placing the two rods together as the upstream and downstream passive control in tandem arrangement has given more hydrodynamics forces reduction than the single rod configurations.Keywords:circular cylinder, passive control, tandem, drag, lift.

Viscous Flow Past a Circular Cylinder Below a Free Surface

2014 ◽  
Author(s):  
Benjamin Bouscasse ◽  
Andrea Colagrossi ◽  
Salvatore Marrone ◽  
Antonio Souto-Iglesias
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Mixing Processes ◽  
Surface Evolution ◽  
Flow Past ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Karman Vortex ◽  
Drag And Lift

Flow past a circular cylinder close to a free surface at low Reynolds and large Froude numbers is investigated numerically using the Smoothed Particle Hydrodynamics model. This meshless method allows for a non-diffusive computation of the free surface evolution, even while breaking and fragmentation may occur. The distance of the cylinder to the free surface, submergence, is varied in order to investigate the detached flow patterns dependence with this factor. Vorticity shed by the cylinder, vortex generation due to free surface breaking, mixing processes, and drag and lift coefficients behavior are discussed. It has been found that, for small submergences, the classical Von Karman vortex shedding from the cylinder does not take place. In turn, moderate vortex shedding occurs, departing not from the cylinder but from vorticity generated at the free surface. This shedding takes places simultaneously with the transport of free surface fluid elements into the bulk of the fluid. It has been also found that for even smaller depth ratios, a vorticity layer remains spatially localized between the cylinder and the free surface, and a stagnation recirculating area develops behind the cylinder. Results are compared with literature finding reasonable qualitatively agreement with experimental works conducted with similar geometrical configuration but larger Reynolds number.

Induced Separation and Vorticity Using Roughness in VIV of Circular Cylinders at 8×103 < Re < 2.0×105

2008 ◽  
Author(s):  
Michael M. Bernitsas ◽  
Kamaldev Raghavan ◽  
G. Duchene
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Fluid Flow ◽  
Circular Cylinder ◽  
Passive Control ◽  
Flow Characteristics ◽  
Grit Size ◽  
Strip Width ◽  
Circular Cylinders ◽  
Flow Past

Results of an experimental investigation on fluid flow past an elastically mounted circular cylinder with rectangular surface roughness strips are presented. Flow characteristics change depending on the strip width, roughness grit size, and location. Roughness size and distribution can be designed to enhance or reduce/suppress VIV amplitude and increase or reduce the range of synchronization, respectively. To the authors’ knowledge this is the first study in passive control of VIV using properly distributed roughness.

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