PIV on Inclined Cylinder Shaped Fish Cages in a Current and the Resulting Flow Field

2008 ◽  
Author(s):  
Astrid Harendza ◽  
Jan Visscher ◽  
Lars Gansel ◽  
Bjo̸rnar Pettersen
Keyword(s):  
Flow Field ◽  
Particle Image ◽  
Three Dimensional ◽  
Structure Change ◽  
Fish Farms ◽  
Three Dimensional Flow ◽  
Towing Tank ◽  
Image Velocimetry ◽  
Fish Cages ◽  
A Current

The present experimental investigation focuses on the flow structure around short free end cylinders with an aspect ratio of L/D = 3 at a Reynolds number of Re = 5000. Cylinders with varying degrees of inclination and porosity were tested in a towing tank, acting as models for fish farm cages. According to studies of fish cages at commercial Norwegian fish farms, the inclination angle of the structure change up to 25 degrees from the vertical when exposed to a current. Cylinders with porosities of 0% and 75% were tested, the latter representing fish cage netting with fouling. To visualize the flow around the cylinders, 2- and 3-Component (2C and 3C) Particle Image Velocimetry (PIV) was used. The effects of inclination and porosity on the three-dimensional flow field will be described and discussed.

scholarly journals Simultaneous Measurement of Free Surface Elevation and Three-Component Velocity Field Around a Translating Surface-Piercing Foil

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
James Schock ◽  
Jason Dahl
Keyword(s):  
Particle Image Velocimetry ◽  
Free Surface ◽  
Velocity Field ◽  
Numerical Methods ◽  
Flow Field ◽  
Particle Image ◽  
Laser Sheet ◽  
Three Dimensional ◽  
Dynamic Mode ◽  
Image Velocimetry

Two methods are investigated to simultaneously obtain both three-dimensional (3D) velocity field and free surface elevations (FSEs) measurements near a surface piercing foil, while limiting the equipment. The combined velocity field and FSE measurements are obtained specifically for the validation of numerical methods requiring simultaneous field data and free surface measurements for a slender body shape. Both methods use stereo particle image velocimetry (SPIV) to measure three component velocities in the flow field and both methods use an off the shelf digital camera with a laser intersection line to measure FSEs. The first method is performed using a vertical laser sheet oriented parallel to the foil chord line. Through repetition of experiments with repositioning of the laser, a statistical representation of the three-dimensional flow field and surface elevations is obtained. The second method orients the vertical laser sheet such that the foil chord line is orthogonal to the laser sheet. A single experiment is performed with this method to measure the three-dimensional three component (3D3C) flow field and free surface, assuming steady flow conditions, such that the time dimension is used to expand the flow field in 3D space. The two methods are compared using dynamic mode decomposition and found to be comparable in the primary mode. Utilizing these methods produces results that are acceptable for use in numerical methods verification, at a fraction of the capital and computing cost associated with two plane or tomographic particle image velocimetry (PIV).

Experimental Study of the Transient Turbulence Generated by a Bubble Using PIV

1999 ◽  
Author(s):  
Javier Ortiz-Villafuerte ◽  
William D. Schmidl ◽  
Yassin A. Hassan
Keyword(s):  
Particle Image ◽  
Three Dimensional ◽  
Small Diameter ◽  
Three Dimensional Flow ◽  
Stagnant Water ◽  
Air Bubble ◽  
Image Velocimetry ◽  
Diameter Pipe ◽  
Transient Velocity ◽  
Bubble Rising

Abstract The particle image velocimetry measurement technique was used to measure the whole-volume, three-dimensional, transient velocity field generated by a single air bubble rising in stagnant water in a small diameter pipe. The three-dimensional flow field was reconstructed using a stereoscopic technique. Conditional averages of the velocity fields for the situations when the bubble rises close to the center of the pipe, and close to the pipe wall were determined, and the turbulent motion generated in the continuous liquid phase for both situations was studied.

The unsteady three-dimensional wake produced by a trapezoidal pitching panel

2011 ◽  
Vol 685 ◽  
pp. 117-145 ◽  
Author(s):  
Melissa A. Green ◽  
Clarence W. Rowley ◽  
Alexander J. Smits
Keyword(s):  
Particle Image ◽  
Three Dimensional ◽  
Qualitative Change ◽  
Strong Interactions ◽  
Stream Velocity ◽  
Near Wake ◽  
Three Dimensional Flow ◽  
Trailing Edge ◽  
Image Velocimetry ◽  
Formation And Evolution

AbstractParticle image velocimetry (PIV) is used to investigate the three-dimensional wakes of rigid pitching panels with a trapezoidal geometry, chosen to model idealized fish caudal fins. Experiments are performed for Strouhal numbers from 0.17 to 0.56 for two different trailing edge pitching amplitudes. A Lagrangian coherent structure (LCS) analysis is employed to investigate the formation and evolution of the panel wake. A classic reverse von Kármán vortex street pattern is observed along the mid-span of the near wake, but the vortices realign and exhibit strong interactions near the spanwise edges of the wake. At higher Strouhal numbers, the complexity of the wake increases downstream of the trailing edge as the spanwise vortices spread transversely and lose coherence as the wake splits. This wake transition is shown to correspond to a qualitative change in the LCS pattern surrounding each vortex core, and can be identified as a quantitative event that is not dependent on arbitrary threshold levels. The location of this transition is observed to depend on both the pitching amplitude and free stream velocity, but is not constant for a fixed Strouhal number. On the panel surface, the trapezoidal planform geometry is observed to create additional vortices along the swept edges that retain coherence for low Strouhal numbers or high sweep angles. These additional swept-edge structures are conjectured to add to the complex three-dimensional flow near the tips of the panel.

The Application of Particle Image Velocimetry (PIV) in a Short-Duration Transonic Annular Turbine Cascade

1992 ◽  
Vol 114 (3) ◽  
pp. 504-509 ◽  
Author(s):  
P. J. Bryanston-Cross ◽  
C. E. Towers ◽  
T. R. Judge ◽  
D. P. Towers ◽  
S. P. Harasgama ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Short Duration ◽  
Particle Image ◽  
Guide Vane ◽  
Three Dimensional ◽  
Film Plane ◽  
Test Facility ◽  
Image Velocimetry

A series of experiments have been performed to demonstrate the application of Particle Image Velocimetry (PIV) to turbomachinery flows. The tests were performed at transonic speeds on a fully annular engine size turbine nozzle guide vane. The vane cascade was installed in a short-duration Isentropic Light Piston Cascade (ILPC) test facility operating with high inlet turbulence levels. The technique has been shown to map the whole flow field with a resolution of 0.5 mm. The quality of the results obtained is not significantly affected by local turbulence rates. The accuracy of the measurements is put at around 4 percent of absolute velocity and is limited by the quality of the image on the film plane. The velocities derived from the PIV images have been compared with predictions from a three-dimensional viscous numerical calculation. It is shown that the experimental and predicted results are in good agreement. It is considered that this technique has considerable potential in application to turbomachinery flow field diagnostics.

Particle Image Velocimetry Measurements of the Three-Dimensional Flow in an Exhaust Hood Model of a Low-Pressure Steam Turbine

2006 ◽  
Vol 129 (2) ◽  
pp. 411-419 ◽  
Author(s):  
Wei Zhang ◽  
Bu Geun Paik ◽  
Young Gil Jang ◽  
Sang Joon Lee ◽  
Su Eon Lee ◽  
...  
Keyword(s):  
Flow Structure ◽  
Large Scale ◽  
Particle Image ◽  
Guide Vane ◽  
Three Dimensional ◽  
Vortical Flow ◽  
Exhaust Hood ◽  
Three Dimensional Flow ◽  
Image Velocimetry ◽  
End Wall

The three-dimensional flow structure inside an exhaust hood model of a low-pressure steam turbine was investigated using a particle image velocimetry (PIV) velocity field measurement technique. The PIV measurements were carried out in several selected planes under design operation conditions with simulated total pressure distribution and axial velocity profile. The mean flow fields revealed a complicated vortical flow structure and the major sources of energy loss. Vortices with different scales were observed inside the exhaust hood: a strong separation vortex (SV) behind the tip of the guide vane, a longitudinal vortex (LV) at the exhaust hood top, a large-scale passage vortex (PV) evolving throughout the flow path, and an end-wall vortex (EWV) in the region adjacent to the front end-wall. Both the SV and the large-scale PV seemed to consume large amounts of kinetic energy and reduce the pressure recovery ability. The results indicate that the steam guide vane and the bearing cone should be carefully designed so as to control the vortical flow structure inside the exhaust hood.

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