Measurements of Turbulence Generated by Oscillating Grid
Publication: Journal of Hydraulic Engineering
Volume 127, Issue 3
Abstract
Turbulence generated by a vertically oscillating grid in a water tank was investigated using the digital particle image velocimetry technique. The statistical turbulence characteristics computed based on the experimental data agree well with the two main findings reported in the literature: (1) The turbulence decays following the power law; and (2) the integral length scale increases linearly with the distance from the grid. In addition, the flow structure near the grid was observed in detail with the advantage of the planar measurements. It was found that the velocity fluctuations in the region near the grid vary depending on the grid geometry. The fluctuations immediately over the bar position are significantly different from those over the grid openings. Turbulence with the highest intensity occurs above the intersection of the square bars that constitute the grid. The results imply that shear flow clearly exists near the grid and homogeneity of the turbulence can only be achieved at a distance from the grid greater than about three mesh sizes. In addition, it was found that at least 400 vector maps should be taken to ensure the accuracy of the measured velocity fluctuations.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Brumley, B. H., and Jirka, G. H. ( 1987). “Near-surface turbulence in a grid-stirred tank.” J. Fluid Mech., Cambridge, U.K., 183, 235–263.
2.
Brunk, B., Weber-Shirk, M., Jensen, A., Jirka, G., and Lion, L. W. (1996). “Modeling natural hydrodynamic systems with a differential-turbulence column.”J. Hydr. Engrg., ASCE, 122(7), 373–380.
3.
De Silva, I. P. D., and Fernando, H. J. S. ( 1992). “Some aspects of mixing in a stratified turbulent patch.” J. Fluid Mech., Cambridge, U.K., 240, 601–625.
4.
E, X., and Hopfinger, E. J. ( 1986). “On mixing across an interface in stably stratified fluid.” J. Fluid Mech., Cambridge, U.K., 166, 227–244.
5.
Ettema, R., Karim, F., and Kennedy, J. F. ( 1984). “Laboratory experiments on frazil ice growth in supercooled water.” Cold Regions Sci. and Technol., 10(1), 43–58.
6.
Hopfinger, E. J., and Toly, J. A. ( 1976). “Spatially decaying turbulence and its relation to mixing across density interfaces.” J. Fluid Mech., Cambridge, U.K., Part 1, 155–175.
7.
Jirka, G. H. ( 1991). “Gas transfer processes at the air/water interface.” Environmental hydraulics, J. H. W. Lee and Y. K. Cheung, eds., Balkema, Rotterdam, The Netherlands, 357–370.
8.
Law, A. W. K., and Wang, H. W. ( 2000). “Measurements of mixing processes with combined digital particle image velocimetry and planar laser induced fluorescence.” Experimental Thermal and Fluid Sci., in press.
9.
Lyn, D. A. ( 1995). “Observations of initial sediment motion in a turbulent flow generated in a square tank by a vertically oscillating grid.” Proc., 1st Int. Conf. on Water Resour., W. Espey Jr. and P. Combs, eds., Vol. 1, ASCE, New York, 608–612.
10.
Lyn, D. A. ( 1997). “A PIV study of an oscillating-grid flow.” Experimental and numerical flow visualization and laser anemometry, Vol. 13, Fluids Engineering Division (Publication), ASME, New York.
11.
McDougal, T. J. ( 1979). “Measurements of turbulence in a zero-mean-shear mixed layer.” J. Fluid Mech., Cambridge, U.K., 94, 409–431.
12.
Nielsen, P. ( 1993). “Turbulence effects on the settling of suspended particles.” J. Sedimentary Petrology, 63(5), 835–838.
13.
Nokes, R. I. ( 1988). “On the entrainment rate across a density interface.” J. Fluid Mech., Cambridge, U.K., 188, 185–204.
14.
Rodi, W. ( 1993). Turbulence models and their application in hydraulics: A state-of-the-art review, Balkema, Rotterdam, The Netherlands.
15.
Rouse, H. ( 1939). “Experiments on the mechanics of sediment suspension.” Proc., 5th Int. Congr. of Appl. Mech., Cambridge, Mass., 550–554.
16.
Thompson, S. M., and Turner, J. S. ( 1975). “Mixing across an interface due to turbulence generated by an oscillating grid.” J. Fluid Mech., Cambridge, U.K., 67, 349–368.
17.
Willert, C. E., and Gharib, M. ( 1991). “Digital particle image velocimetry.” Experiments in Fluids, 10, 181–193.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 127 • Issue 3 • March 2001
Pages: 201 - 208
History
Received: Feb 15, 2000
Published online: Mar 1, 2001
Published in print: Mar 2001
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.