摘要
工程中存在大量的圆形断面细长结构,其常在强风下发生大幅振动,在细长圆柱的风荷载测试中,由于风洞尺寸的限制,常常采用不同长细比的试验模型进行测试,因此长细比是影响该类结构气动力测试结果的重要试验参数之一。采用刚性模型测压风洞试验,对亚临界、临界区及超临界区不同长细比圆形断面柱体中心局部气动力及风压分布随长细比的变化规律进行分析。结果表明:对于采用4倍直径端板的有限长度圆柱模型,跨中气动力特性随着长细比的变化规律并不连续,在亚临界区,当长细比小于等于9时,跨中的气动力结果受长细比的影响较大,与二维圆柱试验结果有较大差异;在临界区,跨中的气动力试验结果受长细比的影响相对较小,并呈现较强的三维特性,若圆柱一侧出现稳定的单分离泡区域,其长细比应大于11;进入超临界区后,当长细比小于等于9时,圆柱的流动状态进入单分离泡流域。
Circular cylinder members are widely used in civil engineering. Wind induced large-amplitude vibration often occurs in slender structures with circular cross-sections. The mostly used testing models are usually sectional models because of the limitation of wind tunnels. Therefore, the aspect ratio is a significant parameter in aerodynamic force test in wind tunnels. The local aerodynamic forces at the middle of the cylinders at the subcritical, critical and supercritical Reynolds number were measured for several models with various aspect ratios through the pressure measurement on rigid section models in the wind tunnel. The results show that the variation of aerodynamic forces is discontinuous along with the change of the aspect ratio, and the variation is different in subcritical, critical and super critical regions, when the end plate with 4 times diameter of the cylinder is mounted. In the subcritical region, when the aspect ratios is less than 9, the aerodynamic results at the span middle are greatly influenced by the aspect ratio, and the results are quite different from the results of the two-dimensional cylinder tests. In the critical Reynolds number range, the results of the aerodynamic test at the span middle are less influenced by the aspect ratio, and exhibit stronger three-dimensional characteristics. The stable single separating bubble could be observed only when the aspect ratio is not less than 11, in supercritical regions, when the aspect ratios is less than 9, the flow state of the cylinder enters into a single separating bubble basin.
引文
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