scholarly journals Drag Reduction of Circular Cylinder in the High-Reynolds-Number Range.

1993 ◽  
Vol 59 (558) ◽  
pp. 342-348 ◽  
Author(s):  
Tsutomu Adachi ◽  
Hiroyuki Maeda ◽  
Masamitsu Shiono ◽  
Tetsuo Ozaki ◽  
Kazuo Matsuuchi ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
High Reynolds Number ◽  
Number Range ◽  
Reynolds Number Range ◽  
High Reynolds

Experimental Results of Flow Nozzle Based on PTC 6 for High Reynolds Number

2014 ◽  
Author(s):  
Noriyuki Furuichi ◽  
Kar-Hooi Cheong ◽  
Yoshiya Terao ◽  
Shinichi Nakao ◽  
Keiji Fujita ◽  
...  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Discharge Coefficient ◽  
Experimental Results ◽  
Flow Conditions ◽  
Number Range ◽  
Discharge Coefficients ◽  
Reynolds Number Range ◽  
Lower Reynolds Number ◽  
High Reynolds

Discharge coefficients for three flow nozzles based on ASME PTC 6 are measured under many flow conditions at AIST, NMIJ and PTB. The uncertainty of the measurements is from 0.04% to 0.1% and the Reynolds number range is from 1.3×105 to 1.4×107. The discharge coefficients obtained by these experiments is not exactly consistent to one given by PTC 6 for all examined Reynolds number range. The discharge coefficient is influenced by the size of tap diameter even if at the lower Reynolds number region. Experimental results for the tap of 5 mm and 6 mm diameter do not satisfy the requirements based on the validation procedures and the criteria given by PTC 6. The limit of the size of tap diameter determined in PTC 6 is inconsistent with the validation check procedures of the calibration result. An enhanced methodology including the term of the tap diameter is recommended. Otherwise, it is recommended that the calibration test should be performed at as high Reynolds number as possible and the size of tap diameter is desirable to be as small as possible to obtain the discharge coefficient with high accuracy.

Further Investigation of Discharge Coefficient for PTC 6 Flow Nozzle in High Reynolds Number

2015 ◽  
Author(s):  
Noriyuki Furuichi ◽  
Yoshiya Terao ◽  
Shinichi Nakao ◽  
Keiji Fujita ◽  
Kazuo Shibuya
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
High Reynolds Number ◽  
Discharge Coefficient ◽  
Flow Region ◽  
Number Range ◽  
Discharge Coefficients ◽  
Reynolds Number Range ◽  
High Reynolds

The discharge coefficients of the throat tap flow nozzle based on ASME PTC 6 are measured in wide Reynolds number range from Red=5.8×104 to Red=1.4×107. The nominal discharge coefficient (the discharge coefficient without tap) is determined from the discharge coefficients measured for different tap diameters. The tap effects are correctly obtained by subtracting the nominal discharge coefficient from the discharge coefficient measured. Finally, by combing the nominal discharge coefficient and the tap effect determined in three flow regions, that is, laminar, transitional and turbulent flow region, the new equations of the discharge coefficient are proposed in three flow regions.

The effects of surface roughness on the flow past circular cylinders at high Reynolds numbers

1982 ◽  
Vol 123 ◽  
pp. 363-378 ◽  
Author(s):  
Y. Nakamura ◽  
Y. Tomonari
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
High Reynolds Number ◽  
Circular Cylinders ◽  
Similarity Parameter ◽  
Number Range ◽  
Pressure Distributions ◽  
Mean Pressure ◽  
Supercritical Range ◽  
High Reynolds

Measurements of’ the mean-pressure distribution and the Strouhal number on a smooth circular cylinder, circular cylinders with distributed roughness, and circular cylinders with narrow roughness strips were made over a Reynolds-number range 4.0 × l04 to 1.7 × l06 in a uniform flow. A successful high-Reynolds-number (trans- critical) simulation for a smooth circular cylinder is obtained using a smooth circular cylinder with roughness strips. High-Reynolds-number simulation can only be obtained by roughness strips and not by distributed roughness. A similarity parameter correlating the pressure distributions on circular cylinders with distributed roughness in the supercritical range is presented. The same parameter can also be applicable to the drag coefficients of spheres with distributed roughness.

Planar Oscillatory Flow Forces at High Reynolds Numbers

1993 ◽  
Vol 115 (1) ◽  
pp. 31-39 ◽  
Author(s):  
J. R. Chaplin
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Number Range ◽  
High Reynolds Numbers ◽  
Reynolds Number Range ◽  
Fine Surface ◽  
High Reynolds

Measurements of pressures around a circular cylinder with fine surface roughness in planar oscillatory flow reveal considerable changes in drag and inertia coefficients over the Reynolds number range 2.5 × 105 to 7.5 × 105, and at Keulegan-Carpenter numbers between 5 and 25. In most respects, these results are shown to be compatible with previous measurements in planar oscillatory flow, and with previous measurements in which the same 0.5-m-dia cylinder was tested in waves.

Hydrodynamic Force Measurements on a Circular Cylinder Fitted With Peripheral Control Cylinders: Preliminary Results on the Development of VIV Suppressors

2015 ◽  
Author(s):  
Mariana Silva-Ortega ◽  
Gustavo R. S. Assi ◽  
Murilo M. Cicolin
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Vortex Shedding ◽  
Hydrodynamic Force ◽  
Force Measurements ◽  
Number Range ◽  
Preliminary Results ◽  
Reynolds Number Range

Recent achievements in controlling the boundary layer by moving surfaces have been encouraging the development and investigation of passive suppressors of vortex-induced vibration. Within this context, the main purpose of the present work is to evaluate the suppression of vortex shedding of a plain cylinder surrounded by two, four and eight smaller control cylinders. Experiments have been carried out on a fixed circular cylinder to investigate the effect of the control cylinders over drag reduction. Control cylinders with diameter of d/D = 0.06 were tested, where D is the diameter of the main cylinder. The gap between the main cylinder and the control cylinders varied between G/D = 0.05 and 0.15. Experiments with a plain cylinder in the Reynolds number range from 5,000 to 50,000 have been performed to serve as reference. It was found that a cylinder fitted with four control cylinders presented less drag and fluctuating lift than cylinders fitted with two or eight small cylinders.

Flow of Surfactant Solutions Past a Circular Cylinder

2004 ◽  
Author(s):  
Yoshihisa Osano ◽  
Satoshi Ogata ◽  
Keizo Watanabe
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Drag Coefficient ◽  
Tap Water ◽  
Surfactant Solution ◽  
Number Range ◽  
Surfactant Solutions ◽  
Reynolds Number Range ◽  
Trade Name

To clarify the effects of surfactant solutions on the drag coefficient of a circular cylinder, the flow past a circular cylinder was investigated in the Reynolds number range of 10 to 7,000 by measuring the drag and by visualizing flow. In addition, the flow pattern was simulated numerically to examine the effect of the viscoelasticity of the surfactant solution. Six cylinders with diameters between 2 and 20 mm were tested, and the ratio of length to diameter (l/d) was 12~48. The test surfactant solutions were aqueous solutions of oleyl-methyldihydroxyethyl ammonium chloride (trade name: Ethoquad O/12) in the concentration range of 50 to 200 ppm and sodium salicylate was added as a counterion. It was clarified that the drag coefficient of surfactant solutions increases comparing with that of tap water in the Reynolds number range of 1,000 < Re 3,000 and drag reduction occurs when Re > 3,000 for a cylinder diameter of 20 mm. The maximum drag reduction ratio was approximately 55% for 200 ppm solution at Re = 7,000. The flow visualization results showed that the drag of surfactant solutions increases because of the existence of the wide stagnant zone around the cylinder. This zone disappeared in the Reynolds number range in which drag reduction occurred. In addition, the width of the wake of surfactant solutions decreases compared with that of tap water, and the Ka´rma´n vortex street is not found. These effects seem to be due to the elasticity caused by the micellar network in surfactant solution.

Drag of a Circular Cylinder in Surfactant Solutions at Intermediate Reynolds Number Range

2003 ◽  
Author(s):  
Satoshi Ogata ◽  
Keizo Watanabe ◽  
Yoshihisa Osano
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Drag Coefficient ◽  
Tap Water ◽  
Surfactant Solution ◽  
Number Range ◽  
Surfactant Solutions ◽  
Cylinder Diameter ◽  
Reynolds Number Range

To clarify the behavior of the drag coefficient of a circular cylinder in the intermediate Reynolds number range, the flow around a circular cylinder in surfactant solutions was investigated experimentally by measurement of the drag in the Reynolds number range of 3 × 102 to 7 × 103. The experiments were performed in a vertical re-circulating water tunnel. The drag coefficient was measured using an apparatus which could measure the drag acting on the circular cylinder directly. Five cylinders of diameter d = 5, 7, 10, 13 and 20 mm were tested, the ratios of length to diameter (l/d) were 12, 24 and 48. The test surfactant solutions were aqueous solutions of Ethoquad O/12 at concentrations of 50, 100 and 200 ppm, and sodium salicylate was added as a counterion. It was clarified that the drag coefficient of the cylinder in surfactant solutions increased comparing that in tap water in the Reynolds number lower approximately 103 < Re < 3 × 103. According to the increase of the Reynolds number, the drag coefficient decreased. When Reynolds number exceeded approximately 103 < Re < 3 × 103, the drag coefficient in surfactant decreased in comparison with that in tap water finally. In other ward, the drag reduction occurred in this Reynolds number range. The maximum drag reduction was about 55% for 200 ppm solution and 20mm diameter at Re ≅ 7 × 103. The value of the drag coefficient in surfactant solutions was dependent on not only (l/d) but also cylinder diameter. The drag coefficient increased with increasing cylinder diameter. The increase in the concentration of surfactant solution emphasized the characteristics of drag reduction and drag increase.

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