摘要
建筑风场数值模拟方法由于具有计算效率高、计算结果处理方便及费用低等优点,得到了广泛的重视和深入的研究。建筑风场数值模拟的成果,其准确性不仅和采用的湍流模型有关,更重要的还和采用的网格系统以及采用的数值计算方法与网格系统的适应性有关。随着作为研究对象的建筑物的外形复杂程度的提高,以及多个建筑物相互影响问题的出现,国内外学者越来越注重网格生成技术的研究。
在目前的建筑风场数值模拟现状中,结构化直角坐标网格、贴体坐标网格和非结构网格都得到不同程度的应用,但是这三种网格有各自的优势也有很明显的限制。吸取结构化直角坐标网格、贴体坐标网格和非结构网格等三种网格形式的优点,切合建筑风场问题的自身特点,建立起一套普遍适用于各种规则与不规则建筑体型的有效的网格生成和数值模拟方法,对建筑风场数值模拟的研究有重要意义。
首先,本文首次提出并自动生成了任意六面体同位网格系统,对于多数建筑风场数值模拟区域通常还是有规则的,可以视为多个初始六面体网格的组成或者最大限度的拟合,采用与结构化直角坐标网格同样的排序对其进行编号,根据控制网格的尺度要求对初始六面体网格进行离散划分,最终生成建筑风场数值模拟通用的任意六面体同位网格系统。该网格系统既保持了结构性网格的数据结构、列式简单的特点,又能如非结构网格一样真实反映复杂边界,网格系统的生成和调整简单而有效,能适合各种规则与不规则建筑体型的建筑风场数值模拟区域的网格生成。
其次,本文针对任意六面体同位网格系统,采用有限体积法建立了控制方程的离散方式,以显式方式对网格非正交性和两相邻单元错位进行了修正,给出了与网格系统相适应的压力校正方程,建立了通用的SIMPLE算法,形成了一套适合建筑风场的任意六面体同位网格系统的数值模拟方法,迄今在国内外尚未见有关上述模式在建筑风场数值模拟中的研究工作的报道。基于上述工作编制了通用的建筑风场数值模拟程序WSB。程序采用FORTRAN语言和MATLAB语言编制,可实现单体和群体建筑风场的数值模拟。
再次,应用开发的WSB程序和任意六面体同位网格系统,对双坡屋面建筑进行了风场模拟,数值模拟结果分别和正立方体网格系统的数值模拟结果以及风洞试验结果进行了比较;也对抗台风试点双坡挑檐低层建筑的风场进行模拟计算,数值模拟结果与非结构网格系统的数值模拟结果和风洞试验结果的进行了比较。这些数值模拟结果表明,程序WSB的网格生成、方程离散和算法实现是正
Numerical modeling of wind fields around buildings has attracted wide attention and has been investigated in depth in recent years, because of its various advantages such as high computational efficiency, convenience in processing numerical results and low cost. The accuracy of the numerical results is not only related to the adopted turbulence model, but more importantly, to the employed grid system and the compatibility between the numerical method and the grid system. As the geometrical configurations of buildings become more complex and the interaction between multiple buildings attracts more attention, more and more importance is being attached to the technique of generating grids.Currently, three kinds of grid systems, i.e., the structured grid systems based on Cartesian coordinates, the grid systems and the non-structured grid systems, are widely used in modeling building wind fields. All these grid systems have their own advantages and limitations. Therefore, it is very important for the numerical modeling to make full use of the advantages of the three kinds of grid systems and consider the peculiar characteristics of the building wind fields in a view to developing a comprehensive numerical model consisting of efficient numerical methods and grid generation techniques which are general and effective for both regular and irregular geometrical configurations.This paper proposed and generated grid systems composed of arbitrary collocated hexahedrons for the first time. It is argued that most modeled domains are regular and can be regarded as integrations of multiple initial grids with hexahedrons or their best approximations. These initial grids are then discretised according to the size control parameter and numbered in the same way as for the structured grids. The general grid system composed of arbitrary collocated hexahedrons is finally generated. This grid system not only keeps the simple data structures as used in the structured grid systems, but also allows complex boundaries to be truly reflected. The grid generation and adjustment are thus very simple and effective, even for very irregular geometrical configurations of buildings.Based on the above-proposed arbitrary collocated grid systems with hexahedrons, this paper uses the finite volume method to discretise the governing equation. Corrections are explicitly made in the source term of the governing equation to consider the negative effects of mesh non-orthogonality and dislocation between adjacent elements. The pressure-corrected equation compatible with the grid systems is also given. The general SIMPLE algorithm is also established. These lead to a comprehensive numerical model for effective and efficient modeling of the wind fields around buildings, which has not been reported in the literature. An in-house computer program, named Wind Simulation of Buildings (WSB), is developed in this study based on the numerical model. This program is coded using FORTRAN and MATLAB languages. It is capable of modeling the wind fields around a single building or a group of buildings.In order to validate the developed program WSB and the proposed arbitrary
collocated hexahedron grid systems, they are first applied to model the wind field around a double-sloped building model. The numerical results are compared with those from the orthogonal grid consisting of cubes and those from the wind tunnel tests respectively. The wind field around a low-rise buildings with gabled roof designed against typhoon is also modeled using WSB and the numerical results are compared with those from non-structured grid system and those from the wind tunnel tests. The numerical results and comparisons indicate that the generation of grid systems, the discretization of governing equations and the implementation of the corresponding algorithms are correct and effective. It is also demonstrated that compared with other grid systems, the proposed arbitrary collocated hexahedron grid systems are more accurate and efficient in modeling wind fields around buildings.Most current research on wind-caused interactions between two or more buildings is limited to two same buildings and the effect is also mainly dependent upon the distance-to-height ratio. Using the program WSB, detailed investigations are conducted in this paper on the wind-caused interactions between two low-rising buildings by changing the geometrical configuration of the disturbing building while keeping that of the disturbed building unchanged.
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