Characteristics of Shear Layer Structure in Skimming Flow over a Vertical Drop Pool
Publication: Journal of Engineering Mechanics
Volume 135, Issue 12
Abstract
The characteristics of shear layer structure between the sliding jet and the pool for skimming flows over a vertical drop pool were investigated experimentally, using flow visualization technique and high speed particle image velocimetry. Four series of experiments having different end sill ratios ( , 0.43, 0.71 and 1.0, where =end sill height and =drop height) with various approaching flow discharges were performed to measure the detailed quantitative velocity fields of the shear layer. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. From the velocity profiles, it is found that the growth of the shear layer in the downward direction as the jet slides down the pool represents the momentum exchange. Analyzing the distribution of measured velocity, the similarity profile of the mean velocity at different cross sections along the shear layer was obtained. The proposed characteristic scales provided unique similarity profiles having promising regression coefficient. The selection of these characteristic scales is also discussed. Further, the spatial variations of mean velocity profiles, turbulence intensities, in-plane turbulent kinetic energy, and Reynolds shear stress were also elucidated in detail. The imperative observation is that the Reynolds shear stress dominates the major part along the shear layer as compared to the viscous shear stress. The study also provides an insight into the flow phenomena through the velocity and turbulent characteristics.
Get full access to this article
View all available purchase options and get full access to this article.
References
Amador, A., Sanchez-Juny, M., and Dolz, J. (2006). “Characterization of the nonaerated flow region in stepped spillway by PIV.” J. Fluids Eng., 128, 1266–1273.
Andreopoulos, J., and Rodi, W. (1984). “Experimental investigation of jets in a crossflow.” J. Fluid Mech., 138, 93–127.
Chang, K. A., Hsu, T. J., and Liu, P. L. F. (2001). “Vortex generation and evolution in water waves propagating over a submerged rectangular obstacle. Part I: Solitary waves.” Coastal Eng., 44(1), 13–36.
Chanson, H. (1994). Hydraulic design of stepped cascades, channels, weirs and spillways, Pergamon, Tarrytown, New York.
Dey, S., and Raikar, R. V. (2007). “Characteristics of horseshoe vortex in developing scour holes at piers.” J. Hydraul. Eng., 133(4), 399–413.
Gilbert, B. (1989). “Turbulence measurements in a flow generated by the collision of radially flowing wall jets.” Exp. Fluids, 7, 103–110.
Hsieh, S. C. (2008). “Establishment of high time-resolved PIV system and application on the characteristics of near-wake flow behind a circular cylinder.” Ph.D. thesis, National Chung-Hsing Univ., Taichung City, Taiwan.
Hussain, A. K. M. F., and Clark, A. R. (1981). “On the coherent structure of the axisymmetric mixing layer: A flow-visualization study.” J. Fluid Mech., 104, 263–294.
Kiyani, G. A., and Rajaratnam, N. (2008). “Discussion: Experimental study on mean velocity characteristics of flow over vertical drop.” J. Hydraul. Res., 46(3), 424–425.
Lin, C., Hsieh, S. C., Kuo, K. J., and Chang, K. A. (2008a). “Periodic oscillation caused by a uniform flow over a vertical drop energy dissipator.” J. Hydraul. Eng., 134(7), 948–960.
Lin, C., Hseih, S. J., Kao, M. J., and Hsu, H. Y. (2004). “Study on mean velocity characteristics of near-wake flow behind a circular cylinder: Application of simultaneous measurement technique by PIV and FLDV.” J. Chinese. Inst. Civil and Hydraul. Eng., 16(1), 73–98.
Lin, C., Hwung, W. Y., Hsieh, S. C., and Chang, K. A. (2007). “Experimental study on mean velocity characteristics of flow over vertical drop.” J. Hydraul. Res., 45(1), 33–42.
Lin, C., Hwung, W. Y., Hsieh, S. C., and Chang, K. A. (2008b). “Reply to the Discussion: Experimental study on mean velocity characteristics of flow over vertical drop.” J. Hydraul. Res., 46(3), 425–428.
Moore, W. L. (1943). “Energy loss at the base of free overfall.” Trans. Am. Soc. Civ. Eng., 108, 1343–1360.
Piirto, M., Saarenrinne, P., Eloranta, H., and Karvinen, R. (2003). “Measuring turbulence energy with PIV in a backward-facing step flow.” Exp. Fluids, 35, 219–236.
Rajaratnam, N. (1976). Turbulent jets, Elsevier, Amsterdam.
Rajaratnam, N., and Chamani, M. R. (1995). “Energy loss at drops.” J. Hydraul. Res., 33(3), 373–384.
Raupach, M. R. (1981). “Conditional statistics of Reynolds stress in rough-wall and smooth-wall turbulent boundary layers.” J. Fluid Mech., 108, 363–382.
Rouse, H. (1936). “Discharge characteristics of the free overfall.” Civ. Eng. (N.Y.), 6, 257.
Yu, C. Z. (1999). Rapidly varied open-channel flow: Theory and applications in hydraulic engineering, Tsinghua University Publication Company, Beijing (in Chinese).
Wygnanski, I., and Fiedler, H. E. (1970). “The two-dimensional mixing region.” J. Fluid Mech., 41(2), 327–361.
Information & Authors
Information
Published In
Copyright
© 2009 ASCE.
History
Received: Oct 24, 2008
Accepted: Apr 3, 2009
Published online: Apr 5, 2009
Published in print: Dec 2009
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.