Flow Behavior Behind Two Side-by-Side Circular Cylinders With Unequal Diameters

2010 ◽  
Author(s):  
Yangyang Gao ◽  
Dingyong Yu ◽  
Soon Keat Tan ◽  
Xikun Wang ◽  
Zhiyong Hao
Keyword(s):  
Average Velocity ◽  
Particle Image ◽  
Flow Behavior ◽  
Water Channel ◽  
Open Water ◽  
Circular Cylinders ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
Pitch Ratio ◽  
Wake Modes

In this study, flow behavior behind two side-by-side circular cylinders with unequal diameters, was investigated by using the technique of particle-image-velocimetry (PIV). The experiments were conducted in a re-circulating open water channel within the subcritical Reynolds number regime and a center-to-center pitch ratio T/D range of 1.2 to 3.6. Instantaneous and average velocity patterns, vorticity and Reynolds stress contours acquired with the PIV were used to analyze the flow behavior behind the two cylinders. The effects of the gap ratio and Re on vortex shedding were studied. The results showed that three flow patterns including the asymmetric biased flow, symmetric biased flow and two wake modes with different scales for different gap ratios respectively were observed.

Flow-pattern identification for two staggered circular cylinders in cross-flow

2000 ◽  
Vol 411 ◽  
pp. 263-303 ◽  
Author(s):  
D. SUMNER ◽  
S. J. PRICE ◽  
M. P. PAÏDOUSSIS
Keyword(s):  
Particle Image ◽  
Cross Flow ◽  
Flow Patterns ◽  
Shear Layers ◽  
Circular Cylinders ◽  
Angle Of Incidence ◽  
Vortex Pairing ◽  
Image Velocimetry ◽  
Pitch Ratio ◽  
Flow Pattern Identification

The flow around two circular cylinders of equal diameter, arranged in a staggered configuration, was investigated using flow visualization and particle image velocimetry for centre-to-centre pitch ratio P/D = 1[ratio ]0 to 5.0 and angle of incidence. α = 0° to 90°. Experiments were conducted within the low subcritical Reynolds number regime, from Re = 850 to 1900. Nine flow patterns were identified, and processes of shear layer reattachment, induced separation, vortex pairing and synchronization, and vortex impingement, were observed. New insight was gained into previously published Strouhal number data, by considering the flow patterns involved. The study revealed that vortex shedding frequencies are more properly associated with individual shear layers than with individual cylinders; more specifically, the two shear layers from the downstream cylinder often shed vortices at different frequencies.

Flow behavior downstream of two side-by-side circular cylinders in shallow water

2016 ◽  
Vol 94 (10) ◽  
pp. 975-981
Author(s):  
Mustafa Atakan Akar ◽  
Burcu Oguz ◽  
Huseyin Akilli ◽  
Besir Sahin
Keyword(s):  
Shallow Water ◽  
Large Scale ◽  
Flow Behavior ◽  
Circular Cylinders ◽  
Small Scale ◽  
Piv Method ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
The Right ◽  
Bistable Flow

Investigations of bistable flow structure past a pair of cylinders positioned side-by-side in shallow water is conducted experimentally applying dye observation and the particle image velocimetry (PIV) method. For the gap ratio of G/D = 1.25, the jet-like flow between cylinders deflects asymmetrical flow structures forming a large-scale wake as well as a small-scale wake downstream of cylinders. The small vortices around the right cylinder get closer to each other forming a larger vortex in the large-scale wake region, which leads the jet-like flow to changeover side to side. The small frequency (f = 0.352 Hz) associated with frequency of vortex shedding of cylinder with wider wake and the higher frequency (f = 0.793 Hz) which depicts the smaller wakes frequency.

Influence of Wall Proximity and Free Surface on Wake of Two Side-by-Side Circular Cylinders: PIV Measurement and POD Analysis

2010 ◽  
Author(s):  
S. S. Paul
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Circular Cylinders ◽  
Particle Image Velocimetry Technique ◽  
Large Scale Structures ◽  
Turbulent Statistics ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Pitch Ratio ◽  
Pod Analysis

The paper reports on an experimental study of turbulent flow around a pair of circular cylinders with a pitch ratio of two. The cylinders were located in the vicinity of a plane wall, in a uniform stream, and adjacent to a free surface in an open channel. The Reynolds number based on depth of flow and fresstream velocity was 30300 while the Froude number was 0.3. A particle image velocimetry technique was used to conduct detailed velocity measurements around and in the near wake region of the cylinder pairs, from which contours and profiles of the mean velocities and turbulent statistics were obtained and discussed. The proper orthogonal decomposition was then applied to provide an insight into the structure of the flow. Reconstruction of the fluctuating velocity components for various numbers of modes were also shown to investigate the role of large-scale structures.

scholarly journals Influence of span-wise coherence on the acoustic radiation in a cylinder wake

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Lars Siegel ◽  
Guosheng He ◽  
Arne Henning ◽  
Karen Mulleners
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Acoustic Radiation ◽  
Maximum Flow ◽  
Flow Speed ◽  
Circular Cylinders ◽  
Cylinder Wake ◽  
Sound Waves ◽  
Image Velocimetry ◽  
Nozzle Size

The aim of this study is to detect and visualise the influence of span-wise coherence on propagating sound waves emanating from a flow around circular cylinders with span-wise variations of the local radius. Synchronous particle image velocimetry (PIV) and microphone measurements are performed in a circular wind tunnel with a nozzle size of 0.4 m×0.4 m at a maximum flow speed of U∞ = 43m s−1 . The test section is surrounded by a full anechoic chamber of approximately 9 m×9 m×5 m.

scholarly journals Experimental Investigation of Flow Structures Around side-by-side Yawed Cylinders in Shallow Water

2019 ◽  
Vol 2 (3) ◽  
pp. 1138-1151
Author(s):  
Ebubekir Kütük ◽  
Umutcan Olmuş ◽  
Tahir Durhasan ◽  
Hüseyin Akıllı
Keyword(s):  
Shear Stress ◽  
Shallow Water ◽  
Vector Fields ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Flow Structures ◽  
Piv Technique ◽  
Gap Ratio ◽  
Image Velocimetry ◽  
Yaw Angle

The aim of this experimental study is to investigate the flow behaviour around two equally yawed side-by-side cylinders in shallow water. Time averaged velocity vector fields, Reynolds shear stress distrubutions and streamline patterns were obtained using Particle Image Velocimetry (PIV) technique. The gap ratio between the cylinders were in the range of G/D=0.25-1.25 with an increment of 0.25 where G is the distance between the cylinders and D is the cylinder diameter. Five different yaw angles of cylinders were employed during the experiment. The results showed that the yaw angle, α had an important effect on the flow structures of the downstream of the cylinders. Reynolds shear stress and vortex structures were decreased, the intensity of the jet like flow were significantly attenuated for the gap ratios of G/D=0.25, 0.50 and 0.75.

scholarly journals PIV of Swirling Flow in a Conical Pipe with Vibrating Wall

2018 ◽  
Vol 10 (02) ◽  
pp. 1850022 ◽  
Author(s):  
Yan Xu ◽  
Yan-Yue Zhang ◽  
Franck C. G. A. Nicolleau ◽  
Zun-Ce Wang
Keyword(s):  
Particle Image ◽  
Swirling Flow ◽  
Water Channel ◽  
Swirling Flows ◽  
Industrial Processes ◽  
Reynolds Stresses ◽  
Pipe Flows ◽  
Velocity Statistics ◽  
Image Velocimetry ◽  
The Mean

Swirling flows in conical pipe can be found in a number of industrial processes, such as hydrocyclone, separator and rotating machinery. It has been found that wall oscillations can reduce the drag in water channel and pipe flows, but there is no study of a swirling flow combined with a vibrating wall in conical pipes, though there are many applications of such combination in engineering processes. A two-dimensional particle image velocimetry (PIV) is used to measure the swirling flow field in a water conical pipe subjected to a periodic vibrating wall for a Reynolds number 3800. The flow velocity statistics are studied under different vibration frequencies corresponding to Strouhal numbers from 60 to 242. The instantaneous axial and vertical velocity in one vibrating period, the mean velocities, and Reynolds stresses were obtained. The results show the existence of an intermediary recirculation cell in the middle of the pipe. They also show that the vibration improves the symmetry for the swirling flow while decreasing dramatically the velocity fluctuation.

scholarly journals Visualization of flow characteristics between the ribbed plates via particle image velocimetry

2019 ◽  
pp. 300-300
Author(s):  
Ilker Goktepeli ◽  
Ulas Atmaca ◽  
Sercan Yagmur
Keyword(s):  
Heat Transfer ◽  
Particle Image Velocimetry ◽  
Flow Separation ◽  
Particle Image ◽  
Reference Model ◽  
Water Channel ◽  
Flow Characteristics ◽  
Advanced Technology ◽  
Particle Image Velocimetry System ◽  
Image Velocimetry

Heat transfer is considerably influenced by flow stagnation, separation and reattachment regions due to the ribbed plates. Placing the ribs such as fins, turbulators that trigger the flow separation, enhances the heat transfer inside the channel by increasing the turbulence intensity. The flow separation is caused by disturbing the thermal and hydrodynamic development lengths. Moreover, these ribs also make an impact that increases the heat transfer by enlarging the heat transfer area. However, the ribs lead to the increment of the required pumping power in the meantime due to the increasing pressure loss in such systems. This aforementioned method is used for the heat exchangers, the solar collectors, the cooling of electronic devices. The investigation of the flow characteristics is very crucial to understand the heat transfer mechanism in the ducts for this reason. In the present paper, the flow characteristics between the plates have been experimentally researched. Particle Image Velocimetry system in the open water channel of Selcuk University Advanced Technology Research and Application Center has been used. The smooth plates have been taken as the reference model and used for the comparison with the plates having the rectangular cross-sectional ribs. The ribs with various heights of 0.1 ? h' = h/H ? 0.3 have been symmetrically placed on the internal surfaces of the plates via several spacing values of 0.5 ? S' = S/H ? 1 for varying Reynolds numbers as 10000 ? Re ? 20000. As a result, the flow characteristics have been given in terms of the contour graphics for velocity vector field, velocity components and vorticity.

Particle Image Velocimetry for Air Flows Behind Permeable Cylinders

2007 ◽  
Author(s):  
Hirotaka Takeuchi ◽  
Yuji Tasaka ◽  
Yuichi Murai ◽  
Yasushi Takeda ◽  
Hideaki Tezuka ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Reverse Flow ◽  
Near Field ◽  
Water Mist ◽  
Circular Cylinders ◽  
Spatial Density ◽  
Turbulence Energy ◽  
Solid Cylinder ◽  
Image Velocimetry

Particle image velocimetry is applied to measurement of airflows around three types of permeable circular cylinders. The experimental model of the permeable cylinder is made of squared meshed sheet rolled in circle. Water mist smoke is used as air tracer, which is generated with dry ice in a chamber to produce fine spatial density fluctuation for guaranteeing the PIV quality. Since the flow involves fluctuation in a very wide wavenumber from the cylinder size to mesh-dependent eddies, calculating brightness spectrum quantitatively assesses the smoke image quality. The experiment is carried out in an open type wind tunnel. The following results are obtained when the measurement results are compared to those of a solid cylinder. 1: The flow just behind the cylinder has forward velocity due to the permeability while the solid cylinder has reverse flow in the wake. This feature relaxes near field excitation of Karman vortex shedding. 2: The reattachment point behind the cylinder displaces several times as the solid case. As a result of the above two phenomena, the peak potion of the turbulence energy appears in the far downstream region as the permeability of the cylinder increases.

Energy Concentration by Bluff Bodies—A Particle Image Velocimetry Investigation

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Eshodarar Manickam Sureshkumar ◽  
Maziar Arjomandi ◽  
Bassam B. Dally ◽  
Benjamin S. Cazzolato ◽  
Mergen H. Ghayesh
Keyword(s):  
Particle Image Velocimetry ◽  
Circular Cylinder ◽  
Bluff Body ◽  
Particle Image ◽  
Transverse Velocity ◽  
Water Channel ◽  
Energy Concentration ◽  
Backward Facing Step ◽  
Flow Energy ◽  
Image Velocimetry

Particle image velocimetry (PIV) of four cylinders with different cross sections were performed in a recirculating water channel at Reynolds numbers of 5000 and 10,000. The cylinders were split into two distinct categories; semicircular and convex-edged triangular (c-triangular) prisms which have a smooth diverging fore-face and a flat, backward facing step aft-face, and a trapezoid which has a flat fore face and a backward-facing step aft-face. The resulting streamwise and transverse velocity vectors (u and v, respectively) were analyzed to provide a qualitative comparison of the bluff body wakes to the circular cylinder, which is the standard upstream stationary body in wake-induced vibration (WIV) energy technology. The Reynolds stresses, turbulent kinetic energy (TKE), mean spanwise vorticity, and the energy in the fluctuating component of the wake were compared. The main findings are: (i) a convex fore-face and a backward-facing step aft face are more effective at converting the flow energy to temporal wake energy (+20%) compared to a circular cylinder, (ii) a trapezoid type shape is less effective at converting flow energy to temporal wake energy (−40%) compared to a circular cylinder, (iii) increasing Reynolds number reduces the efficiency of conversion of upstream flow energy to downstream transverse temporal energy. Utilizing stationary upstream bodies such as the semicircle and the c-triangle can result in concentrating more energy in the fluctuating components for the downstream transversely vibrating bluff body in a WIV system, and hence can realize in more efficient WIV technology.

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