Investigation of Flow Around and in Wake of a Heated Circular Cylinder at Moderate Reynolds Numbers

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
P. Michálek ◽  
S. Pospíšil ◽  
M. Macháček ◽  
V. Michalcová
Keyword(s):  
Circular Cylinder ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Special Technique ◽  
Cylinder Surface ◽  
Cylinder Wall ◽  
Low Reynolds Numbers ◽  
Contour Maps ◽  
Image Velocimetry ◽  
Wake Patterns

Abstract The flow around a heated circular cylinder and the wake behind it were studied in wind tunnel flow using two methods of anemometry, i.e., particle image velocimetry (PIV) and constant temperature anemometry (CTA) with a special technique using a rotating slanted hot-wire probe. The Reynolds number ranged from 2000 to 20,000 and the cylinder wall temperatures varied between 27 °C and 177 °C. The wake is characterized by mean wind and fluctuation contour maps. Significant changes in wake patterns were observed while the cylinder was being heated, thus increasing its wall temperatures at low Reynolds numbers. At higher Reynolds numbers, the effects of cylinder heating on wake properties were negligible. The research fills a gap observed in the literature for a certain combination of velocity, cylinder aspect ratio, and cylinder surface temperature.

scholarly journals Characterization of Mixing in a Simple Paddle Mixer Using Experimentally Derived Velocity Fields

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Douglas Bohl ◽  
Akshey Mehta ◽  
Naratip Santitissadeekorn ◽  
Erik Bollt
Keyword(s):  
Fluid Transport ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Velocity Fields ◽  
Cylinder Wall ◽  
Finite Time Lyapunov Exponents ◽  
Image Velocimetry ◽  
Flow Reynolds Number ◽  
Paddle Mixer

The flow field in a cylindrical container driven by a flat bladed impeller was investigated using particle image velocimetry (PIV). Three Reynolds numbers (0.02, 8, 108) were investigated for different impeller locations within the cylinder. The results showed that vortices were formed at the tips of the blades and rotated with the blades. As the blades were placed closer to the wall the vortices interacted with the induced boundary layer on the wall to enhance both regions of vorticity. Finite time lyapunov exponents (FTLE) were used to determine the lagrangian coherent structure (LCS) fields for the flow. These structures highlighted the regions where mixing occurred as well as barriers to fluid transport. Mixing was estimated using zero mass particles convected by numeric integration of the experimentally derived velocity fields. The mixing data confirmed the location of high mixing regions and barriers shown by the LCS analysis. The results indicated that mixing was enhanced within the region described by the blade motion as the blade was positioned closed to the cylinder wall. The mixing average within the entire tank was found to be largely independent of the blade location and flow Reynolds number.

Experimental Investigation of an Acoustic Field Influence on a Development of the Plane Microjet by Particle Image Velocimetry (PIV)

2011 ◽  
Vol 6 (4) ◽  
pp. 42-50
Author(s):  
Yuriy Litvinenko ◽  
Maria Litvinenko ◽  
Mikhail Katasonov
Keyword(s):  
Particle Image Velocimetry ◽  
Acoustic Field ◽  
Vector Fields ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Laser Flash ◽  
Piv Measurements ◽  
Low Reynolds Numbers ◽  
Image Velocimetry ◽  
Field Influence

An acoustic field influence on a development of the plane microjet at low Reynolds numbers were investigated experimentally employing Particle Image Velocimetry (PIV). Measurements were performed at synchronization of an acoustic signal phase with a laser flash. Instantaneous velocity fields of different cross- and longitudinal sections are occurred. Receptivity of the plane microjet to transversal acoustic disturbances is shown. PIV-images, correspond to them vector fields and vorticity fields are presented

NUMERICAL AND EXPERIMENTAL ANALYSES OF THE FLOW AROUND A HORIZONTAL WALL-MOUNTED CIRCULAR CYLINDER

2009 ◽  
Vol 33 (2) ◽  
pp. 189-215 ◽  
Author(s):  
M. Sami Akoz ◽  
M. Salih Kirkgoz
Keyword(s):  
Numerical Modeling ◽  
Circular Cylinder ◽  
Numerical Solutions ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Sensitivity Study ◽  
Cylinder Surface ◽  
Image Velocimetry ◽  
Horizontal Wall ◽  
Drag And Lift

The numerical modeling of two-dimensional turbulent flow around a horizontal wall-mounted circular cylinder at Reynolds numbers in the range of 1000≤ReD≤7000 is investigated. Ansys® 10.0-FLOTRAN program package is used to solve the governing equations by finite element method, and the performance of the standard k-ε, standard k-ω and SST turbulence models are examined. A sensitivity study for the three turbulence models is carried out on eight computational meshes with different densities and structures. The computational velocity fields from the present simulations are compared with the experimental results obtained from particle image velocimetry (PIV) measurements for validation purposes. The point of the boundary layer detachment from the cylinder surface and the lengths of primary and secondary separation regions occurring around the cylinder are determined numerically and compared with those obtained experimentally. From these comparisons it is found that the numerical modeling using either of k-ω and SST turbulence models is reasonably successful. Using the results of numerical solutions, the drag and lift coefficients, Cd and Cl, are also calculated and compared with the measured values.

The Flow Around an Impulsively Started Square Prism

2010 ◽  
Author(s):  
Nelson Tonui ◽  
David Sumner
Keyword(s):  
Circular Cylinder ◽  
Recirculation Zone ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Temporal Development ◽  
Near Wake ◽  
Towing Tank ◽  
Streamwise Location ◽  
Square Prism ◽  
Image Velocimetry

The flow around a square prism impulsively set into motion was studied experimentally using particle image velocimetry (PIV). The experiments were conducted in an X-Y towing tank for Reynolds numbers from Re = 200 to 1000 and dimensionless acceleration parameters from a* = 0.5 to 10. The temporal development of the near-wake recirculation zone, and its pair of primary eddies, was examined from the initial start until the wake became asymmetric. When considering the time elapsed from the start of motion, the temporal development of the wake was sensitive the initial acceleration. “Impulsively started” conditions were effectively attained for a* ≥ 3. However, when considering the distance traveled from the start of motion, the wake parameters were sensibly independent of a* for a* ≥ 0.5. Concerning the temporal development of the recirculation zone, the length of the recirculation zone, the streamwise location of the primary eddies, and the strength of the primary eddies increased with time following the impulsive start, while the cross-stream spacing of the eddy centres remained nearly constant. The recirculation zone of the square prism was longer than that of the impulsively started circular cylinder but shorter than an impulsively started flat plate. For t* > 2, the primary eddy strength, maximum vorticity, and cross-stream spacing of the primary eddies were the same for both the square prism and circular cylinder.

An Investigation on the Lift Mechanism of Flapping-Wing Air Vehicle

2014 ◽  
Vol 971-973 ◽  
pp. 353-358 ◽  
Author(s):  
Feng Bao ◽  
Jin Wen Yang ◽  
Qi Yang ◽  
Xiang Xiang Fu
Keyword(s):  
Particle Image ◽  
Angle Of Attack ◽  
Reynolds Numbers ◽  
Flapping Wing ◽  
Stream Velocity ◽  
Low Reynolds Numbers ◽  
Image Velocimetry ◽  
Air Vehicle ◽  
Lift Mechanism ◽  
The Difference

This paper deals with the aerodynamical problems of rigid flapping wing at low Reynolds numbers with emphasis on investigating the lift generation mechanism of simplified ornithopter. Theoretical analysis and Particle Image Velocimetry (PIV) were conducted to analyze and verify the lift generation conditions. The results revealed that the rigid flapping wing will generate lift under the conditions of both angle of attack α and free incoming flow velocity v were not zero. With the wings flapped periodically, there were votexes formed, developed and shedding alternately. The calculation of curl demonstrated that the greater of flapping speed, the greater of curl. The statistic of circulation suggested that the circulation generation of flapping down was greater than that of flapping up, the circulation difference contributed to the lift generation. The difference of circulation will increase along with the angle of attack α in the circumstances of free stream velocity v and flapping speed π and flapping amplitude Φ matched well.

scholarly journals Particle image velocimetry measurement of turbulent wake past circular cylinder at Reynolds numbers from 2.5·103 to 1.5·104

2021 ◽  
Vol 345 ◽  
pp. 00030
Author(s):  
Ondřej Sterly
Keyword(s):  
Particle Image Velocimetry ◽  
Circular Cylinder ◽  
Particle Image ◽  
Transverse Velocity ◽  
Reynolds Numbers ◽  
Particle Image Velocimetry Technique ◽  
Recirculation Bubble ◽  
Image Velocimetry ◽  
Ensemble Statistics ◽  
Vorticity Component

A canonical case of air flow past a circular cylinder is studied by using Particle Image Velocimetry technique. This contribution focus to the ensemble statistics (first and second moment) of the stream-wise and transverse velocity component as well as to the in-plane vorticity component. Although the range of explored Reynolds numbers is narrow, we observe a significant shortening of recirculation bubble within this range.

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.

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