Numerical Investigations on Flow Around a Two-Dimensional Trapezoidal Bluff Body

• Main Authors: Hung Lan Chen, 陳鴻嵐
• Other Authors: Furman F.M. Fang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/75555306997363644080

碩士 === 國立中興大學 === 土木工程學系 === 89 === Investigation on flow around a bluff body has been an important subject in building research. To evaluate the dynamic response of a structure, the flow effects on the body and related flow characteristics are necessary during the design stage. Nowadays, there are mostly obtained by wind tunnel model testings. However, the accuracy of the experimental results usually suffers from scale effect. Besides, the achievement of the complete flow data is generally costly. Therefore, the application of high-speed computation in flow simulation becomes an important way of the analyses. The objective of the study is to investigate numerically the turbulent flow around a two dimensional trapezoidal bluff body. In the study, a weakly-compressible-flow method incorporated with a space-average large-eddy-simulation technique is adopted. By varying the shape of the trapezoidal deck section and the attack angle of the approaching flow, the resulting surrounding flow characteristics and the wind effect on the body are assessed. Results show that the major influence of the flow characteristics is the approaching-flow attack angle. As the geometric angle of the trapezoidal body increases, the mean drag coefficient also increases. On the other hand, as the attack angle increases, the mean lift coefficient also increases. When the angle of attack is zero the root-mean-square values of the drag and lift coefficient become minimum. When the attack angle is small, the spectrum of lift coefficient shows a single peak. Generally, a better wind effect on the body is obtained as the geometric angle equals 15o. However, it may result in a large fluctuating lift force at a large attack angle. Finally, The general characteristics of the flow remains unchanged as Reynolds number exceeds about 105.