Effect of Helical Strakes Around a Finned Tube on Aeolian Tone

2011 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Yuki Ito ◽  
Ryunosuke Kamo ◽  
Eiichi Nishida
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Vortex Shedding ◽  
Large Diameter ◽  
Small Diameter ◽  
Finned Tube ◽  
Spanwise Direction ◽  
Helical Strakes ◽  
Karman Vortex ◽  
High Reynolds

In the present paper, the characteristics of vortex shedding and Aeolian tone radiated from a finned tube with helical strakes were experimentally investigated. The helical strakes are mounted spirally around a serrated finned tube surface. We measured the turbulence intensity in the wake, velocity fluctuation spectrum, the coherence of velocity fluctuations in the spanwise direction and SPL spectrum. The Aeolian tone radiated from the finned tube with helical strakes at high Reynolds number was smaller than the case of no helical strakes. The helical stakes were effective to reduce the Aeolian tone radiated from the finned tube. And the existence of helical strakes of large diameter caused the decrease of the periodicity and the turbulence intensity in the wake of the finned tube. The coherent scale of Karman vortex in the spanwise direction is smaller than that of a finned tube without helical strakes. However, the effect of helical strakes of small diameter on vortex shedding depended on the Reynolds number. The Karman vortex was clearly formed even in the case of helical strakes of small diameter at low Reynolds number. The existence of helical strakes of small diameter around a finned tube caused the increase of the periodicity of vortex shedding from a finned tube. The coherent scale of Karman vortex in the spanwise direction was larger than that of a finned tube without helical strakes.

VIV Suppression Device Development and the Perils of Reynolds Number

2017 ◽  
Author(s):  
Don W. Allen ◽  
Nicole Liu
Keyword(s):  
Reynolds Number ◽  
Small Diameter ◽  
Reynolds Numbers ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Helical Strakes ◽  
Low Reynolds ◽  
Offshore Industry ◽  
High Reynolds ◽  
Viv Suppression

Most deepwater tubulars experiencing high currents frequently require vortex-induced vibration (VIV) suppression to maintain an acceptable fatigue life. While helical strakes and fairings are by far the most popular VIV suppression devices used in the offshore industry today, a myriad of small alternations to these basic devices can significantly impact the observed levels of suppression effectiveness. Additionally, numerous novel VIV reduction devices are continually being developed and some new devices are progressing towards the product readiness phase. It is quite common to first test suppression devices at low Reynolds numbers due to the availability of smaller scale facilities that are typically more budget-friendly than larger scale facilities. For larger scale testing, it is usually simpler and less expensive to evaluate prototype suppression devices on shorter pipe sections that are spring mounted rather than test on longer flexible pipes. This paper utilizes results from historical VIV experiments to evaluate the merits of various test setups and scales and to underscore the importance of Reynolds number. An assortment of testing scales are presented including: a) small diameter tests at low Reynolds numbers; b) moderate diameter tests that incorporate at least part of the critical Reynolds number range; c) short pipe tests conducted at prototype Reynolds numbers; and d) long pipe tests conducted at high Reynolds numbers but at less than full scale suppression geometry. The use of computational fluid dynamics (CFD) is also briefly discussed.

Effect of Fins on Vortex Shedding Noise Generated From a Circular Cylinder in Cross Flow

2010 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Yuji Kouno ◽  
Eiichi Nishida
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Finned Tube ◽  
Pressure Level ◽  
Spanwise Direction ◽  
Equivalent Diameter ◽  
Karman Vortex ◽  
Bare Tube

In the present paper, the effect of twist-serrated fins around a bare tube on the Aeolian tone was experimentally investigated. These fins were mounted spirally around a bare tube and had the same geometry as those actually used in boiler tubes. We measured the intensity of velocity fluctuation, spectrum of velocity fluctuation, coherence of Karman vortex in the spanwise direction, dynamic lift force, and sound pressure level of the aerodynamic noise generated from finned tubes with various fin pitches. An Aeolian tone induced by Karman vortex shedding was observed in the case of a finned tube, although the complicated fin was mounted around a bare tube. A decrease in the pitch of the fin effectively caused an increase in the equivalent diameter, which acted as the characteristic length of a cylinder with fins. The equivalent diameter depended on the Reynolds number. We modified a relation to calculate the characteristic diameter of the finned tube, which in turn was used to calculate the Strouhal number. The coherent scales in the spanwise direction for the cases with various fin pitches were slightly larger than that of a simple circular cylinder. It is known that the sound pressure level of the Aeolian tone depends on the coherent scale of the Karman vortex in the spanwise direction. However, when the pitch of the fins decreased, the peak level of the sound pressure spectrum decreased. A correlation analysis between the flow field and Aeolian tone was carried out.

Cellular vortex shedding in the wake of a tapered plate

2008 ◽  
Vol 617 ◽  
pp. 355-379 ◽  
Author(s):  
VAGESH D. NARASIMHAMURTHY ◽  
HELGE I. ANDERSSON ◽  
BJØRNAR PETTERSEN
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Vortex Shedding ◽  
High Reynolds Number ◽  
Three Dimensional ◽  
Base Pressure ◽  
Recirculation Bubble ◽  
Apparent Lack ◽  
Secondary Motion ◽  
High Reynolds

Direct numerical simulation (DNS) of vortex shedding behind a tapered plate with the taper ratio 20 placed normal to the inflow has been performed. The Reynolds numbers based on the uniform inflow velocity and the width of the plate at the wide and narrow ends were 1000 and 250, respectively. For the first time ever cellular vortex shedding was observed behind a tapered plate in a numerical experiment (DNS). Multiple cells of constant shedding frequency were found along the span of the plate. This is in contrast to apparent lack of cellular vortex shedding found in the high-Reynolds-number experiments by Gaster & Ponsford (Aero. J., vol. 88, 1984, p. 206). However, the present DNS data is in good qualitative agreement with similar high-Reynolds-number experimental data produced by Castro & Watson (Exp. Fluids, vol. 37, 2004, p. 159). It was observed that a tapered plate creates longer formation length coupled with higher base pressure as compared to non-tapered (i.e. uniform) plates. The three-dimensional recirculation bubble was nearly conical in shape. A significant base pressure reduction towards the narrow end of the plate, which results in a corresponding increase in Strouhal number, was noticed. This observation is consistent with the experimental data of Castro & Rogers (Exp. Fluids, vol. 33, 2002, p. 66). Pressure-driven spanwise secondary motion was observed, both in the front stagnation zone and also in the wake, thereby reflecting the three-dimensionality induced by the tapering.

721 Effects of Helical Strakes on Karman Vortex Shedding from a Circular Cylinder with Serrated Fin

2004 ◽  
Vol 2004 (0) ◽  
pp. _721-1_-_721-5_
Author(s):  
Hiromitsu HAMAKAWA ◽  
Tohru FUKANO ◽  
Masaki ANDO ◽  
Eiichi NISHIDA
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Helical Strakes ◽  
Karman Vortex

502 Effect of Helical Strakes around a Serrated Fin Tube on Karman Vortex Shedding

2005 ◽  
Vol 2005 (0) ◽  
pp. 159-160
Author(s):  
Tomohiro KUDO ◽  
Hiromitsu HAMAKAWA ◽  
Kouji KOMATSU ◽  
Tohru FUKANO ◽  
Masaki ANDO ◽  
...  
Keyword(s):  
Vortex Shedding ◽  
Helical Strakes ◽  
Karman Vortex ◽  
Fin Tube

Vortex shedding from a hydrofoil at high Reynolds number

2005 ◽  
Vol 531 ◽  
pp. 293-324 ◽  
Author(s):  
DWAYNE A. BOURGOYNE ◽  
STEVEN L. CECCIO ◽  
DAVID R. DOWLING
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
High Reynolds Number ◽  
High Reynolds

Turbulence Pattern in Triangular Cylinder

2011 ◽  
Vol 110-116 ◽  
pp. 4719-4722
Author(s):  
V. Parthiban ◽  
Ashwin Russelle
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Numerical Method ◽  
Vortex Shedding ◽  
Velocity Vector ◽  
High Reynolds Number ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
High Reynolds ◽  
Solution Velocity

In order to predict a turbulent flow around a triangular cylinder a high Reynolds number of 45000 is done in the numerical simulation. In this simulation both steady and unsteady vortex shedding is predicted and various time steps. The numerical method used in this simulation is Reynolds Stress model. For steady and unsteady solution velocity contours and velocity vector plots is to be predicted for the vortex shedding behind the triangular cylinder.

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