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Characteristics of water flow field around an air bubble attached at top of a downward-inclined pipe
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
2013 (English)In: ISTP 24: Proceedings of the 24th International Symposium on Transport Phenomena, Yamaguchi, Japan, 1-5 November 2013, 2013Conference paper (Refereed)
Abstract [en]

Flow visualization techniques and high time-resolved PIV were used to investigate the characteristics of water flow field around a stationary air bubble attached at the top of inner-wall of a fully-developed, downward-inclined pipe. Experiments were carried out in a downward-inclined pipe having a slope of 4o, a constant inner diameter of 9.6 cm, and a length of 260.0 cm. Two settling water chambers with different still water levels were connected to the inlet and outlet of the downward-inclined pipe. A pump having a power of 4 Hp was installed between two chambers and used to drive the flow through the inclined pipe. A tilting, honeycomb-like flow regulator made of many straws was placed in front of the pipe entrance in order to smooth the inlet flow. Titanium dioxide powder being uniformly dispersed in the pipe flow was used as tracer both for flow visualization tests and for PIV measurements. The results not only show that horseshoe vortex and reverse flow generated, respectively, at the upstream and downstream of the air bubble can be easily observed in all test cases; but also depict that the flow bifurcates around the stagnation point located at the leading edge of air bubble and prominent formation of the shear layer starts from the separation point and evolves right beneath the air bubble. Based on the precise determination of the specific length scale bs (indicating the representative thickness of a shear layer with the center position being located at ysc) and the specific velocity scale (u – us2) (showing the velocity deficit between the lower and upper bounds of the shear layer), a similarity profile can be obtained with the form of (u – us2)/(us1 – us2) versus the dimensionless shifted height, (y – ysc)/bs , for the mean streamwise velocity in the shear layer beneath the air bubble.

Place, publisher, year, edition, pages
National Category
Civil Engineering
URN: urn:nbn:se:kth:diva-179754OAI: diva2:889233
24th Int. Symp. Transport Phenomena, Nov 2013, Yamaguchi, Japan

QC 20160104

Available from: 2015-12-22 Created: 2015-12-22 Last updated: 2016-01-04Bibliographically approved

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