Investigating the characteristics of surface oscillations of flow through obstacles using Roshko and Ursell dimensionless numbers

Document Type : Research Article

Authors

1 Master's graduates of Civil_River Engineering, Shahid Chamran university of Ahvaz, Iran

2 Assistant Professor, Faculty of Engineering, Arak University, Arak, Iran

Abstract

Vortex is shed by flow collision with obstacles in its path. If the frequency of vortex shedding equals the frequency of natural oscillations of flow, resonance will be created and transverse oscillation perpendicular to flow with greatest wave amplitude will occur. In this study, in order to investigate the characteristics of the transverse wave caused by the vortex shedding of the obstacles, 135 cylinder barriers with a diameter of 20 mm in 5 different configurations were arranged in the laboratory flume. In total, 900 tests were carried out which variables were flow discharge, average flow depth, channel slope, longitudinal and transverse distance between obstacles. In each test, after the formation of transverse oscillations, their characteristics including amplitude and frequency of wave were recorded. Then, the effective variables on transverse wave characteristics and their effects on the involved dimensionless numbers were investigated. The results indicated whatever the flow discharge is increased, the maximum wave amplitude due to resonance occurs in larger average flow depth, which has more amount. Also by changing the longitudinal distance of obstacles, Roshko’s changes relative to increasing of Ursell were ascending at the beginning and they were reversed after reaching a certain range of Ursell number; moreover, by increasing the flow discharge, the rate of Ursell changes relative to Roshko decreased. Finally, by using dimensional analysis and statistical software, the equations between Roshko with Ursell and Froude numbers were proposed for each of the modes I and II and the validation of equations were approved (R2= 0.92).

Keywords

Main Subjects

References

[1]J. H. Lienhard, Synopsis of lift, drag and vortex frequency data for rigid circular cylinder, Washington State University, (1966).
[2] J. H. Arakeri, Collapse of the tacoma narrows bridge, Resonance Journal of Science Education, 10(8) (2005) 97-102.
[3] J. C. Schuster, Canal capacity, wave formation by bridge piers, Denver, Colorado, 1967.
[4] A. M. Howes, Canal wave oscillation phenomena due to column vortex shedding, Utah State University, Logan, Utah, 2011.
[5] K. Zhaoa, N. S. Chengb, Z. Huangcd, Experimental study of free-surface fluctuations in open-channel flow in the presence of periodic cylinder arrays, Journal of Hydraulic Research, 52(4) (2014) 465-475.
[6] X. Liu, Y. Zeng, Drag coefficient for rigid vegetation in subcritical open channel, in: 12th International conference on hydroinformatics, ELSEVIER, (2016) 1124-1131.
[7]V. Dupuis, S. Proust, C. Berni, A. Paquier, Combined effects of bed friction and emergent cylinder drag in open channel flow, Environ Fluid Mech, 16(6) (2016) 1173-1193.
[8]K. Zhao, N.-S. Cheng, X. Wang, S.K. Wang, Measurements of fluctuation in drag acting on rigid cylinder array in open channel flow, Journal of Hydraulic Engineering, 140 (2014) 48-55.
[9] A. C. d. Lima, N. Izumi, Linear stability analysis of open-channel shear flow generated by vegetation, Journal of Hydraulic Engineering, 140(3) (2014) 231240.
[10] L. Zima, N. Ackermann, Wave Generation in Open Channels by Vortex Shedding from Channel Obstructions, Journal of Hydraulic Engineering,128(6)(2002)596-695 .
[11]   M. Ghomeshi, S. A. Mortazavi-Dorcheh, R. Falconer, Amplitude of wave formation by vortex shedding in open channel, Journal of Applied Science, 7 (24) (2007) 3927-3934.
[12]   A. Jafari, M. Ghomeshi, M. Bina, S.M. Kashefipour, Experimental study on ten modes of transverse waves due to vertical cylinders in open channels, Journal of Food, Agriculture & Environment, 8(2) (2010) 949-955.
[13]   R. G. Dean, R.A. Dalrymple, Water wave mechanics for engineers and scientists, World Scientific, Cornell University, USA, 1984.
[14]   R. Azizi, M. Ghomeshi, Relationship between the frequency of transverse waves and characteristics of the flow and obstacles in open channel, Journal of Iran-Water Resource Research, 6(2) (2010) (In Persian).
[15]   A. Sarkar, Vortex-Excited Transverse Surface Waves in an Array of Randomly Placed Circular Cylinders, Journal of Hydraulic Engineering, 138(7) (2012) 610618.
[16]   A. Defina, I. Pradella, Vortex-induced cross-flow seiching in cylinder arrays, Journal of Advances in Water Resources, 71 (2014) 140-148.
[17]   D. P. Viero, I. Pradella, A. Defina, Free surface waves induced by vortex shedding in cylinder arrays, Journal of Hydraulic Research, 55(1) (2017) 16-26.
[18]   M. H. Purmohammadi, M. Ghomeshi, S.H.Musavi, Impact of Prismatic-Shaped Obstacle on the Characteristics of Transverse Waves, Journal of Water and Soil Science, 25(2) (2015) 117-128 (In Persian).
[19]   M. H. Purmohammadi, M. Ghomeshi, S.H. Mosavi Jahromi, S.M. KashefiPour, M. Fathi Moghadam, The Study of Impact of Obstacle Shape on The Characteristics of Transverse Waves, Journal of Irrigation Sciences and Engineering Scientific, 39(1) (2016) 11-20 (In Persian).
[20]   S. Mostafavi, M. Ghomeshi, B. Shahmoradi, Study of Maximum Relative Amplitude Formation Due To Vortex Shedding Of Submerged Obstacles, Journal of Irrigation Sciences and Engineering Scientific, 39(3) (2016) 209-215 (In Persian).
[21]   S. Mostafavi, M. Ghomeshi, B. Shahmoradi, Resonance Frequency of Transverse Waves Due to Vortex Shedding of Obstacles with Different Arrangements, Water and Soil Science, 27(1) (2017) 147-157  (In Persian).
[22]   B. Shahmoradi, M. Ghomeshi, S. Mostafavi, Experimental Investigation of the Effect of Submerged Cubic Obstacles on The Transverse Wave In A Rectangular Channel, Journal of Irrigation Sciences and Engineering Scientific, 40(1-1) (2017) 27-37 (In Persian).
[23]   D. Ormières, M. Provansal, Transition to turbulence in the wake of a sphere, The American Physical Society, 83 (1999) 80-83.Society, 83 (1999) 80-83.
Amirkabir Journal of Civil Engineering
Volume 51, Issue 5
November and December 2019
Pages 963-978

Files

Share

How to cite

Statistics