Abstract: With the computational fluid software Fluent, the Realizable k-ε turbulence model was used to simulate the flow characteristics of the tandem double trapezoidal column with different spacing ratios under the Reynolds number Re=6.6×105. Seven kinds of interval ratios with interval ratio S* between 0.5~6 were selected to explain the aerodynamic coefficient, vorticity diagram and streamline diagram of the double trapezoidal column. The results show that the flow characteristics of tandem trapezoidal columns are similar to tandem cylinders and rectangular columns, and there are three modes of flow with different spacing ratios: Mode Ⅰ(Shieldeing regime), Mode Ⅱ (Reattachment regime) and Mode Ⅲ (impinging regime). There is critical interval ratio S*cr between modes. A shielding area is generated between the double trapezoidal columns at the interval ratio of S*<1; the upstream trapezoidal column trails reattach to the upper and lower surfaces of the downstream trapezoidal column at 1<S*<3. The double trapezoidal column forms its own vortex shedding at S*<3, and the vortex of the downstream changes from a single row of alternating drop (Mode Ⅰ) to a double row of drop (Mode Ⅱ, Mode Ⅲ) with the increase of the interval ratio. Affected by the upstream trapezoidal column trails, the structural stability and aerodynamic parameters of Mode Ⅰ are better than those of other modes.

Key words:

tandem trapezoidal column, interval ratio, Reynolds number, flow characteristics, vortex shedding, structural stability