Self-sustained oscillations between two tandem cylinders at Reynolds number 1,000

Self-sustained oscillations between two tandem cylinders at Reynolds number 1,000 This study focuses on the self-sustained oscillatory flow characteristics between two tandem circular cylinders of equal diameter placed in a uniform inflow. The Reynolds number (Re D ), based on the cylinder diameter, was around 1,000 and all experiments were performed in a recirculating water channel. The streamwise distance between two tandem cylinders ranged within 1.5 ≤ X c/D ≤ 7.0. Here X c denotes the center-to-center distance between two tandem cylinders. For all experiments studied herein, quantitative velocity measurements were performed using hot-film anemometer and the LDV system. The laser sheet technique was employed for qualitative flow visualization. The wavelet transform was applied to elucidate the temporal variation and phase difference between two spectral components of the velocity signals detected in the flow field. The remarkable finding was that when two tandem circular cylinders were spaced at a distance within 4.5 ≤ X c/D ≤ 5.5, two symmetrical unstable shear layers with a certain wavelength were observed to impinge onto the downstream cylinder. The responding frequency (f u ), measured between these two cylinders, was much higher than the natural shedding frequency behind a single isolated cylinder at the same Re D . This responding frequency decreased as the distance X c/D increased. Not until X c/D ≥ 6.0, did it recover to the natural shedding frequency behind a single isolated cylinder. Between two tandem cylinders, the Strouhal numbers (St c = f u X c/Uc) maintained a nearly constant value of 3, indicating the self-sustained oscillating flow characteristics with a wavelength X c/3. Here U c is the convection speed of the unstable shear layers between two tandem cylinders. At Re D  = 1,000, the self-sustained oscillating characteristics between two tandem circular cylinders were proven to exhibit a sustained flow pattern, not just a sporadic phenomenon. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Self-sustained oscillations between two tandem cylinders at Reynolds number 1,000

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Publisher
Springer Journals
Copyright
Copyright © 2007 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-007-0409-9
Publisher site
See Article on Publisher Site

Abstract

This study focuses on the self-sustained oscillatory flow characteristics between two tandem circular cylinders of equal diameter placed in a uniform inflow. The Reynolds number (Re D ), based on the cylinder diameter, was around 1,000 and all experiments were performed in a recirculating water channel. The streamwise distance between two tandem cylinders ranged within 1.5 ≤ X c/D ≤ 7.0. Here X c denotes the center-to-center distance between two tandem cylinders. For all experiments studied herein, quantitative velocity measurements were performed using hot-film anemometer and the LDV system. The laser sheet technique was employed for qualitative flow visualization. The wavelet transform was applied to elucidate the temporal variation and phase difference between two spectral components of the velocity signals detected in the flow field. The remarkable finding was that when two tandem circular cylinders were spaced at a distance within 4.5 ≤ X c/D ≤ 5.5, two symmetrical unstable shear layers with a certain wavelength were observed to impinge onto the downstream cylinder. The responding frequency (f u ), measured between these two cylinders, was much higher than the natural shedding frequency behind a single isolated cylinder at the same Re D . This responding frequency decreased as the distance X c/D increased. Not until X c/D ≥ 6.0, did it recover to the natural shedding frequency behind a single isolated cylinder. Between two tandem cylinders, the Strouhal numbers (St c = f u X c/Uc) maintained a nearly constant value of 3, indicating the self-sustained oscillating flow characteristics with a wavelength X c/3. Here U c is the convection speed of the unstable shear layers between two tandem cylinders. At Re D  = 1,000, the self-sustained oscillating characteristics between two tandem circular cylinders were proven to exhibit a sustained flow pattern, not just a sporadic phenomenon.

Journal

Experiments in FluidsSpringer Journals

Published: Nov 25, 2007

References

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