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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water engineering : Hybrid investigation of air transport processes in moderately sloped stepped spillway flows
Hybrid investigation of air transport processes in moderately sloped stepped spillway flows
In stepped spillway flows, a self-aerated flow region is often found where large quantities of air may be entrained into the
water body. This air is then mixed with the water phase leading to an air-water mixture flow with different characteristics
than the clear water flow. Thus, air entrainment is an important flow feature which needs to be considered for safe design
of these hydraulic structures. Advances in the development of new air-water measurement techniques and numerical
modeling capabilities allow addressing these complex problems. Computational Fluid Dynamics (CFD) modeling can be a
powerful supplement for physical model tests.
In the presented study, the self-aeration process and the subsequent air transport in the aerated flow region of a stepped
spillway model is investigated by means of both, new experimental and numerical methods. The slope of the spillway
model is 1:2 and different flow rates are considered involving a skimming flow regime. For the physical model tests, a
double-tip conductivity probe and ultrasonic sensors are used to evaluate air-water flow properties and flow depths,
respectively. Additionally, high-speed camera recordings help to qualitatively analyze the air-water transport.
In the numerical model, the same stepped spillway is simulated with identical flow conditions. A RANS approach coupled
with RNG k-ŠĆ turbulence modeling and a VOF technique for free surface tracking is used. The determination of the
inception point and the entrained air quantities are estimated employing a subscale model. To verify the numerical model,
results are compared to the laboratory air-water measurements. The comparison of results from both techniques helps to
identify their capabilities and limitations.
File Size : 3,074,786 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water engineering
Date Published : 12/08/2015
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