Flow-Induced Motion of an Elastically Mounted Circular Cylinder With Roughness Strips at Different Angles of Attack

2016 ◽  
Author(s):  
Li Zhang ◽  
Qiyang Shangguan ◽  
Lin Ding ◽  
Yanrong Chen ◽  
Qianyun Ye
Keyword(s):  
Circular Cylinder ◽  
Transverse Direction ◽  
Angle Of Attack ◽  
Cylinder Surface ◽  
Wake Region ◽  
Fluid Structure Interactions ◽  
Near Wake ◽  
Amplitude Response ◽  
Induced Motion ◽  
Simulation Results

Flow-induced motions (FIM) of an elastically mounted circular cylinder with roughness strips at different angles of attack are investigated by 2-D URANS simulations based on the open source CFD tool OpenFOAM. The cylinder is constrained to one degree of freedom motion in the transverse direction. Two selectively distributed roughness strips on cylinder surface are used to enhance the FIM of the cylinder. Simulations are conducted at Re = 60,000 and Re = 100,000 with the angle of attack, αattack, varies from 0° to 90°. Amplitude response, frequency response, and near-wake structures of the cylinder are discussed in numerical results. The simulation results indicate that both suppression and enhancement of FIM are observed for the cylinder as the angle of attack rises from 0° to 90°. For αattack≥ 55°, the near-wake region becomes quite slender and vortex shedding is suppressed. The FIM of the cylinder is greatly inhibited when αattack ≥55°. In addition, a complex vortex reattachment observed in the near-wake region intensifies the fluid-structure interactions and causes obviously higher amplitude.

Numerical investigation of near-wake characteristics of cavitating flow over a circular cylinder

2016 ◽  
Vol 790 ◽  
pp. 453-491 ◽  
Author(s):  
Aswin Gnanaskandan ◽  
Krishnan Mahesh
Keyword(s):  
Circular Cylinder ◽  
Single Phase ◽  
Three Dimensional ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Cavitating Flow ◽  
Cylinder Surface ◽  
Near Wake ◽  
Eddy Simulation ◽  
Wake Characteristics

A homogeneous mixture model is used to study cavitation over a circular cylinder at two different Reynolds numbers ($Re=200$ and 3900) and four different cavitation numbers (${\it\sigma}=2.0$, 1.0, 0.7 and 0.5). It is observed that the simulated cases fall into two different cavitation regimes: cyclic and transitional. Cavitation is seen to significantly influence the evolution of pressure, boundary layer and loads on the cylinder surface. The cavitated shear layer rolls up into vortices, which are then shed from the cylinder, similar to a single-phase flow. However, the Strouhal number corresponding to vortex shedding decreases as the flow cavitates, and vorticity dilatation is found to play an important role in this reduction. At lower cavitation numbers, the entire vapour cavity detaches from the cylinder, leaving the wake cavitation-free for a small period of time. This low-frequency cavity detachment is found to occur due to a propagating condensation front and is discussed in detail. The effect of initial void fraction is assessed. The speed of sound in the free stream is altered as a result and the associated changes in the wake characteristics are discussed in detail. Finally, a large-eddy simulation of cavitating flow at $Re=3900$ and ${\it\sigma}=1.0$ is studied and a higher mean cavity length is obtained when compared to the cavitating flow at $Re=200$ and ${\it\sigma}=1.0$. The wake characteristics are compared to the single-phase results at the same Reynolds number and it is observed that cavitation suppresses turbulence in the near wake and delays three-dimensional breakdown of the vortices.

scholarly journals Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 294
Author(s):  
Dongdong Shao ◽  
Li Huang ◽  
Ruo-Qian Wang ◽  
Carlo Gualtieri ◽  
Alan Cuthbertson
Keyword(s):  
Mass Transport ◽  
Near Field ◽  
Lateral Spreading ◽  
Wake Flow ◽  
Wake Region ◽  
Near Wake ◽  
Turbulence Characteristics ◽  
Macro Scale ◽  
Flow Turbulence ◽  
Fish Cages

Cage-based aquaculture has been growing rapidly in recent years. In some locations, cage-based aquaculture has resulted in the clustering of large quantities of cages in fish farms located in inland lakes or reservoirs and coastal embayments or fjords, significantly affecting flow and mass transport in the surrounding waters. Existing studies have focused primarily on the macro-scale flow blockage effects of fish cages, and the complex wake flow and associated near-field mass transport in the presence of the cages remain largely unclear. As a first step toward resolving this knowledge gap, this study employed the combined Particle Image Velocimetry and Planar Laser Induced Fluorescence (PIV-PLIF) flow imaging technique to measure turbulence characteristics and associated mass transport in the near wake of a steady current through an aquaculture cage net panel in parametric flume experiments. In the near-wake region, defined as ~3M (mesh size) downstream of the net, the flow turbulence was observed to be highly inhomogeneous and anisotropic in nature. Further downstream, the turbulent intensity followed a power-law decay after the turbulence production region, albeit with a decay exponent much smaller than reported values for analogous grid-generated turbulence. Overall, the presence of the net panel slightly enhanced the lateral spreading of the scalar plume, but the lateral distribution of the scalar concentration, concentration fluctuation and transverse turbulent scalar flux exhibited self-similarity from the near-wake region where the flow was still strongly inhomogeneous. The apparent turbulent diffusivity estimated from the gross plume parameters was found to be in reasonable agreement with the Taylor diffusivity calculated as the product of the transverse velocity fluctuation and integral length scale, even when the plume development was still transitioning from a turbulent-convective to turbulent-diffusive regime. The findings of this study provide references to the near-field scalar transport of fish cages, which has important implications in the assessment of the environmental impacts and environmental carrying capacity of cage-based aquaculture.

Aspects of Shear Layer Unsteadiness in a Three-Dimensional Supersonic Wake

2005 ◽  
Vol 127 (6) ◽  
pp. 1085-1094 ◽  
Author(s):  
Alan L. Kastengren ◽  
J. Craig Dutton
Keyword(s):  
Shear Layer ◽  
Stream Flow ◽  
Free Stream ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Base Flow ◽  
Recirculation Region ◽  
Side View ◽  
Near Wake ◽  
Supersonic Wake

The near wake of a blunt-base cylinder at 10° angle-of-attack to a Mach 2.46 free-stream flow is visualized at several locations to study unsteady aspects of its structure. In both side-view and end-view images, the shear layer flapping grows monotonically as the shear layer develops, similar to the trends seen in a corresponding axisymmetric supersonic base flow. The interface convolution, a measure of the tortuousness of the shear layer, peaks for side-view and end-view images during recompression. The high convolution for a septum of fluid seen in the middle of the wake indicates that the septum actively entrains fluid from the recirculation region, which helps to explain the low base pressure for this wake compared to that for a corresponding axisymmetric wake.

Fluid dynamic effects of grooves on circular cylinder surface

AIAA Journal ◽  
1991 ◽  
Vol 29 (12) ◽  
pp. 2062-2068 ◽  
Author(s):  
Takeyoshi Kimura ◽  
Michihisa Tsutahara
Keyword(s):  
Circular Cylinder ◽  
Fluid Dynamic ◽  
Cylinder Surface ◽  
Dynamic Effects

Study of the Laminar Free-Convection Wake Above an Isothermal Vertical Plate

1973 ◽  
Vol 95 (3) ◽  
pp. 289-294 ◽  
Author(s):  
N. E. Hardwick ◽  
E. K. Levy
Keyword(s):  
Free Convection ◽  
Vertical Plate ◽  
Fluid Motion ◽  
Heated Plate ◽  
Two Dimensional ◽  
Wake Region ◽  
Hot Wire ◽  
Near Wake ◽  
Steady Laminar ◽  
Finite Difference Techniques

The steady, laminar, two-dimensional wake above a thin vertical isothermal heated plate cooled by free convection was investigated theoretically and experimentally. The system of partial differential equations governing the fluid motion and heat transfer in the vicinity of the plate and in the near wake region was formulated and solved using finite difference techniques. Using air, the temperature and velocity profiles in the wake region were measured experimentally using a laser holographic interferometer and a constant temperature hot wire anemometer.

Sign in / Sign up

Export Citation Format

Share Document