Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
The goal of this study is to investigate the characteristics of mean drag and lift forces for a series of cylinders arranged in tandem with varying flow turbulence and surface roughness. This goal was fulfilled by building a wind tunnel test section capable of generating both smooth flow and turbulent flow, and by adopting cylinder models with certain types of surface roughness as well as the smooth surface. In both smooth flow and grid-turbulence flow conditions, single cylinders as well as multiple cylinders were tested. The tested Reynolds number ranged from 2.7×104 to 8.6×104. For multiple-cylinder tests, a majority of the tests were conducted with cylinders aligned in tandem or as tops-leveled for unequal diameter cases. A limited number of experiments were conducted for different alignment cases as the comparison. The mean drag and lift coefficients were reported for individual cylinders as well as for combinations. A significant effect of flow turbulence was observed on both drag coefficients and lift coefficients. The critical spacing was observed for most combinations in the smooth flow condition, which featured with an abrupt change of drag coefficients with a small change of spacing. However, this feature was much less pronounced when these combinations were tested in the turbulent flow. It was also found that for the combinations with larger cylinder in the upstream position, large combined drag coefficients and small lift coefficients were more likely to occur, especially in the smooth-flow conditions. The force ratios were reported for all the tested combinations, which measure the reduction of the combined drag force compared to the sum of the drag forces when the cylinders stand independently. Results of force ratios showed that there was more reduction with more cylinders in the tandem group, and the reduction became less when the spacing between the cylinders increased. Recommendations for the design practice were developed based on the force ratios obtained from the tests in the turbulent flow condition.
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Liu, Xianzhi, "Wind loads on multiple cylinders arranged in tandem with effects of turbulence and surface roughness" (2003). LSU Master's Theses. 2653.