Effects of Free-Stream Turbulence and Reynolds Number on the Aerodynamic Characteristics of a Semicylindrical Roof
Publication: Journal of Structural Engineering
Volume 141, Issue 9
Abstract
The influences of free-stream turbulence and Reynolds number on the aerodynamic characteristics of a semicylindrical roof have been investigated experimentally under uniform flow conditions. Grids were used to generate homogeneous turbulent flows with turbulence intensities varying from 5.7 to 12.2%. The diameters, , of the semicylindrical roof models were 0.2 and 0.6 m. The Reynolds numbers based on ranged from to in smooth flow and from approximately to in grid-generated turbulent flow. Measurements of the surface pressure indicated that, in smooth flow, the mean and RMS pressure distributions became Reynolds number independent when . The introduction of turbulence has caused a premature transition of the separated shear layer from laminar to turbulent. Increasing free-stream turbulence helps to remarkably reduce the mean and fluctuating drag force at lower Reynolds number, . There is also a relatively significant reduction in the mean lift force as the turbulence intensity increases when . The data also suggested that the effects of turbulence essentially depend on the turbulence intensity and the ratio of turbulence length scale to cylinder diameter. The small-scale turbulence was better able to interact with the surface boundary layer before and after separation and thus dramatically increased the pressure fluctuations in both the top and wake regions.
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Acknowledgments
This study was financially supported by the National Natural Science Foundation of China under Grant Numbers 91215302, 51278160 and 51378147.
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© 2014 American Society of Civil Engineers.
History
Received: Feb 25, 2014
Accepted: Oct 24, 2014
Published online: Nov 21, 2014
Discussion open until: Apr 21, 2015
Published in print: Sep 1, 2015
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