大跨平屋盖表面锥形涡流动模型研究

Flow model of conical vortices on large-span flat roof

基于大跨平屋盖表面旋涡流动显示试验,对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,建立简化的二维锥形涡流动模型,给出旋涡上部流速、旋涡内部流线曲率以及屋面涡核吸力之间的定量关系。据此流动模型分析表明,旋涡内部流线曲率越大,旋涡转速越快,旋涡强度越高,且后者的影响更为显著。根据流动显示试验结果,量化各风向下大跨平屋盖表面锥形涡强度。通过考虑旋涡效应对准定常理论进行修正,给出旋涡涡核吸力的计算式,并将计算值与大跨平屋盖刚性模型风洞测压试验数据进行对比,验证锥形涡流动模型对于预测旋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 was established by adding transitional region between the vortex core and the potential flow region of the Rankine vortex.Through this flow model,a relationship between the flow above the vortices,the curvature radius of flow streamlines in the vortices and the suctions beneath vortex cores was given.The flow model indicats that the larger the curvature of flow streamlines and the faster the vortex spins,the greater the intensity of vortex is.The effect of rational velocity on intensity of vortices is more obvious.Through measured velocities by flow visualization and parameters of vortices,the intensities of conical vortices on a large-span flat roof under different wind directions were provided.The quasi-steady theory was corrected by including the effect of vortices.With this two-dimensional vortex model and the corrected quasi-steady theory,mean and peak suctions beneath cores of conical vortices can be predicted,which were verified by measured pressures on a larger-scale model of the large-span flat roof.