折叠网壳结构风致雪漂效应的数值模拟研究

发布时间：2019-06-29 10:04

【摘要】：野营折叠网壳帐篷被广泛应用于民用和军事领域,此类房屋通过编织材料组成其防护层和构造层,致使房屋自重在整个荷载中所占比重很小,属于典型的轻型房屋,故风和雪荷载是其结构设计的主要控制荷载。针对风荷载目前已有相对深入的研究,而对于雪荷载,风致雪漂效应会造成积雪在折叠网壳屋盖表面产生不均匀分布,其结果常会导致结构局部或整体坍塌,且现行《建筑结构荷载规范》(GB50009-2012)仅根据以往的设计经验和国际标准以及国外有关资料概括性地规定了典型规则屋面积雪分布系数,并不能适用于目前大量涌现的外形独特且对雪荷载敏感的轻质屋盖结构,故亟需对折叠网壳结构的风雪效应进行深入研究与探讨。在风致雪漂移的研究方法中,现场实测可以获得最准确的数据,但是所需周期长,较大程度上受制于自然条件等因素;试验研究受到试验条件和相似准则的限制致使耗费成本过高。随着计算机技术的高速发展,CFD(Computational Fluid Dynamics)数值模拟技术以其周期短、成本低、易满足相似性和高重复性模拟的优点被广泛且深入地应用于风雪运动的研究。为了深入研究风致折叠网壳结构表面积雪分布规律,本文基于欧拉-欧拉方法和空气相与雪相均连续且单向耦合的基本假定,考虑风雪漂移的跃移运动模式和悬移运动模式,运用大型通用计算流体动力学软件ANSYS Fluent中的Mixture多相流模型理论,采用自编C语言UDF解释型程序与Fluent作接口实现边界条件的嵌入,并计及壁面上积雪侵蚀与沉积,建立风致雪漂的数值计算模型。首先模拟三维算例立方体模型周围的积雪分布,探讨与分析数值风洞的关键技术与参数,在与实测结果对比后验证所建立数值模型的可行性与有效性,分析表明三方程klk--ω湍流模型具有较优模拟结果。在此基础上,以风速、风向角和地貌类型为分析参数,模拟折叠网壳结构的风致雪漂效应,求解风雪流流场后分析风雪耦合场规律,并获得结构表面风致雪漂的积雪分布系数,为近似该体型结构的抗风雪设计提供参考依据。结果表明:风雪流绕流具有复杂体型的折叠网壳结构异常紊乱,较低风速的持续作用下对其表面积雪分布尤为不利,结构表面积雪的侵蚀与沉积受风向角影响会发生在不同区域,总体呈现以侵蚀为主、背风面局部沉积的规律,因风向角的变化引起同一分区雪荷载的改变对此类雪荷载敏感性结构的抗风雪设计至关重要,此外,结构表面积雪沉积系数与四类地貌的开阔程度呈现负相关性。
[Abstract]:Camping folding reticulated shell tent is widely used in civil and military fields. This kind of house is composed of protective layer and structural layer through braided materials, which makes the proportion of building weight in the whole load very small, so it belongs to typical light building, so wind and snow load is the main control load of its structural design. At present, the wind load has been studied relatively deeply, but for the snow load, the snow drift effect caused by the wind will cause the uneven distribution of snow on the surface of the folded reticulated shell roof, and the results often lead to the local or overall collapse of the structure, and the current Code of Building structure load (GB50009-2012) only specifies the snow distribution coefficient of the typical regular roof according to the previous design experience and international standards, as well as the relevant foreign data. It is not suitable for a large number of lightweight roof structures with unique shape and sensitive to snow load, so it is urgent to study and discuss the snowstorm effect of folded reticulated shell structure. In the research method of wind-induced snow drift, the most accurate data can be obtained from the field measurement, but the required period is long, which is restricted to a large extent by natural conditions, and the experimental research is limited by the test conditions and similar criteria, resulting in too high cost. With the rapid development of computer technology, CFD (Computational Fluid Dynamics) numerical simulation technology has been widely and deeply used in the study of snow movement because of its short cycle, low cost, easy to meet the advantages of similarity and high repeatability simulation. In order to deeply study the snow distribution law on the surface of wind-induced folded reticulated shell structure, based on the Euler-Euler method and the basic assumption that the air phase and snow phase are continuous and unidirectional coupling, considering the jump motion mode and suspension motion mode of snow drift, the Mixture multiphase flow model theory in large-scale general computational fluid dynamics software ANSYS Fluent is used, and the interface between self-compiled C language UDF explanatory program and Fluent is used to realize the embedding of boundary conditions. Taking into account the erosion and deposition of snow on the wall, the numerical model of wind-induced snow drift is established. Firstly, the snow distribution around the cube model of a three-dimensional example is simulated, and the key techniques and parameters of the numerical wind tunnel are discussed and analyzed. The feasibility and effectiveness of the numerical model are verified by comparing with the measured results. The analysis shows that the three-equation klk-- 蠅 turbulence model has better simulation results. On this basis, taking wind speed, wind direction angle and geomorphological type as analysis parameters, the wind-induced snow drift effect of folded reticulated shell structure is simulated, the law of wind-snow coupling field is analyzed after solving the wind-snow flow field, and the snow distribution coefficient of wind-induced snow drift on the surface of the structure is obtained, which provides a reference for the anti-snow design of the similar structure. The results show that the folding reticulated shell structure with complex shape is abnormally disordered, and the snow distribution on the surface is particularly disadvantageous under the continuous action of low wind speed. The erosion and deposition of snow on the surface of the structure will occur in different areas under the influence of wind direction angle, which is dominated by erosion and local deposition on the leeward surface. The change of snow load in the same zone caused by the change of wind direction angle is very important to the anti-snow design of this kind of snow load sensitive structure. In addition, the snow deposition coefficient on the surface of the structure is negatively correlated with the openness of the four geomorphology.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU399;TU312.1

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