American Society of Civil Engineers


Redistribution of Velocity and Bed-Shear Stress in Straight and Curved Open Channels by Means of a Bubble Screen: Laboratory Experiments


by K. Blanckaert, (ICARE-ENAC, Ecole Polytechnique Fédérale, CH-1015 Lausanne, Switzerland; and, Fac. of Civ. Engrg. and Geosciences, Delft Univ. of Technol., The Netherlands. E-mail: koen.blanckaert@epfl.ch), F. A. Buschman, (Hydro. and Quantitative Water Mgmt. Group, Wageningen Univ., Nieuwe Kanaal 11, 6709 PA Wageningen, The Netherlands), R. Schielen, (Ministry of Transport, Public Works and Water Mgmt., Inst. for Inland Water Mgmt. and Waste Water Treatment, P.O. Box 9072, 6800 ED arnhem, The Netherlands), and J. H. A. Wijbenga, (HKV Consultants, P.O. Box 2120, 8203AC Lelystad, The Netherlands)

Journal of Hydraulic Engineering, Vol. 134, No. 2, February 2008, pp. 184-195, (doi:  http://dx.doi.org/10.1061/(ASCE)0733-9429(2008)134:2(184))

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Document type: Journal Paper
Abstract: Open-channel beds show variations in the transverse direction due to the interaction between downstream flow, cross-stream flow, and bed topography, which may reduce the navigable width or endanger the foundations of structures. The reported preliminary laboratory study shows that a bubble screen can generate cross-stream circulation that redistributes velocities and hence, would modify the topography. In straight flow, the bubble-generated cross-stream circulation cell covers a spanwise extent of about four times the water depth and has maximum transverse velocities of about 0.2 ms-¹. In sharply curved flow, it is slightly weaker and narrower with a spanwise extent of about three times the flow depth. It shifts the counter-rotating curvature-induced cross-stream circulation cell in the inwards direction. Maximum bubble-generated cross-stream circulation velocities are of a similar order of magnitude to typical curvature-induced cross-stream circulation velocities in natural open-channel bends. The bubble screen technique is adjustable, reversible, and ecologically favorable. Detailed data on the 3D flow field in open-channel bends is provided, which can be useful for validation of numerical models.


ASCE Subject Headings:
Open channels
Bending
Secondary flow
Bubbles
Experimentation
Shear stress
Velocity
Curvature