马鞍屋盖表面锥形涡流动模型研究

A MODEL OF SADDLE ROOF TOP SURFACE PRESSURES PRODUCED BY CONICAL VORTICES

该文基于大跨平屋盖和马鞍屋盖表面锥形涡流动显示试验,对现有的兰金涡模型进行改进,在其涡核区与势流区之间添加过渡区,从而建立了简化的二维锥形涡流动模型,给出了旋涡上部流速、旋涡内部流线曲率以及屋面涡核吸力之间的定量关系。据此流动模型,分析了旋涡强度的影响因素即为旋涡内部流线曲率和旋涡流速:旋涡内部流线曲率越大,旋涡转速越快,旋涡强度越大。基于流动显示试验和测压试验所得平屋盖以及马鞍屋盖表面各旋涡参数之比,以平屋盖表面锥形涡为基准,量化了各风向下马鞍屋盖表面的锥形涡强度。通过加入考虑旋涡效应对传统准定常理论进行修正,给出了锥形涡涡核吸力(均值、峰值)的计算公式,并将计算值与马鞍屋盖刚性模型风洞测压试验数据进行对比,验证了锥形涡流动模型对于预测马鞍表面锥形涡涡核吸力的有效性。

Based on measured velocities in conical vortices by flow visualization, a simplified two-dimensional vortex model is established by adding transitional region between the vortex core and the potential flow region of the Rankine vortex. Through this flow model, a relationship linking the flow above the vortices, the curvature radius of flow streamlines in the vortices and the suctions beneath vortex cores is obtained. Two factors contributing to the intensity of vortices are identified as the curvature radius of flow streamline and the velocity in vortices. A larger curvature of flow streamlines and a faster vortex spins lead to a greater intensity of vortex. By flow visualization and pressure measurement, the ratio for parameters of conical vortices on a flat roof and two saddle roofs with different rise-span ratios are analyzed. Then the intensities of conical vortices on the two saddle roofs under different wind directions are given, based on the standard intensity of conical vortices on the flat roof. The quasi-steady theory is improved by including the effect of vortices. With this two-dimensional vortex model and the improved quasi-steady theory, the mean and peak suctions beneath cores of conical vortices on the two saddle roofs are predicted, which are verified by comparing calculated and measured pressures on larger-scale models of saddle roof.