Mechanism of aerodynamic control in the strong wind and its applicability to an extremely high rise building

本研究的目的是开发一种通过改变建筑物的转角形状来降低高于大气边界层深度的高层建筑风荷载的方法。首先，我们讨论了一种方形截面圆柱体由于切角和圆角而减小气动力的性能。分别在均匀和湍流两种条件下进行了风洞试验。在此基础上，采用直接有限差分格式，在不引入湍流模型的情况下，对具有不同转角形状的方柱体的三维不可压缩流动进行了数值模拟。在均匀流动的情况下，研究了气动力与流动结构的关系，重点研究了分离剪切层的再附着和尾迹中涡的形成。为了在上述数值结果的基础上阐明各种接近气流中气动力减小的机理，采用风洞试验的方法研究了均匀流动和紊流条件下二维和三维圆柱体的表面压力特性。关于强风，我们认为大气边界层的特征与更高层的特征有很大的不同。在观测资料的基础上，我们成功地模拟了风洞中的大气边界层。我们注意到加热器产生的热分层与安装在风洞底板上的块体产生的湍流之间的关系。证实了产生气流的有效性，阐明了大气湍流的垂直结构。测量了某高层建筑模型在热分层紊流逼近过程中的气动力，阐明了其特点。所得结论可为某超高层建筑在大气边界层上的抗风设计提供参考。少

The purpose of this study is to develop the method of the reduction in wind loading on a tall building which is higher than the depth of the atmospheric boundary layer by means of modification of the corner shape of the building. First we discuss the performance for the reduction of aerodynamic forces on a type of square section cylinder due to corner-cutting and corner-rounding. Wind tunnel tests were carried out in uniform and turbulent flow. After that three-dimensional incompressible flow around a square cylinder with various corner shapes are numerically simulated by direct finite difference scheme without any turbulence model. The relation between aerodynamic force and flow structures is examined in case that the approaching flow is uniform, focusing on reattachment of the separated shear layers and vortex formation in the wake. In order to clarify the mechanism of aerodynamic force reduction in various approaching flows on the basis of the above numerical results, the surface pr … More essure characteristics acting on a two- and three- dimensional cylinders in uniform and turbulent flows are investigated by means of wind tunnel tests.Concerning the strong wind we suppose that the characteristics in the atmospheric boundary layers are quite different from those in the further upper layer. On the basis of observation data, we succeed in modeling an atmospheric boundary layer in the wind tunnel. We pay attention to the relation between the thermal stratification generated by the heaters and the turbulence generated by the blocks mounted on the floor of the wind tunnel. We confirm the validity of generated airflow and clarify the vertical structures of the atmospheric turbulence. The aerodynamic forces of a tall building model are measured in the approaching turbulent flow with thermal stratification and their characteristics are clarified. The conclusion are obtained as the available guide for wind resistant design of an extremely high rise building over the atmospheric boundary layer. Less