兰州大学机构库 >土木工程与力学学院
二维粗糙壁面上湍流流动特性的数值模拟
Alternative TitleNumerical Simulation of Turbulent Flow Characteristics on Two-Dimensional Rough Wall
王鹏
Thesis Advisor武生智
2018-05-01
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword粗糙壁面 压差阻力 摩擦阻力 零平面位移高度 空气动力学粗糙度
Abstract

近地层壁面上的流动是风沙物理学和结构风工程领域中最重要的研究课题之一。近壁面流场结构的描述可以正确认识和预测流体的行为,所以对近壁面流场结构的研究是非常关键的。因此本文的研究工作如下:1.简要回顾了国内外学者关于流体流经近地面时的湍流特性和近壁面流场结构两个方面的研究现状,从理论研究、数值模拟研究和风洞试验研究三个方面进行了归纳和分析;2.针对自然界中存在的建筑物、植被层、草方格和石方格等粗糙壁面,提出了简化的离散粗糙单元模型进行了数值分析。计算得到,压差阻力系数在相邻粗糙单元的间距与高度比为7时达到最大值;通过摩擦阻力系数的计算分析,得到了流场再附点的位置,且该值与已有的结果相吻合。基于流动阻力计算得到空气动力学粗糙度和零平面位移高度,发现空气动力学粗糙度在间距与高度比为6时达到最大;3.针对沙波纹,沙丘等风成地形地貌简化为余弦函数形的连续粗糙单元,并对其构成的粗糙壁面进行数值分析。结果表明:压差阻力系数随着波长与振幅比的增大而减小。通过对曲面壁面上的摩擦阻力系数的计算分析,得到位于波峰后面尾涡脱落的分离点和再附点的位置。连续粗糙单元构成的粗糙壁面上的零平面位移高度和空气动力学粗糙度可通过流动阻力计算得到。在不同的雷诺数作用下,压差阻力系数、摩擦阻力系数和零平面位移高度随风速的增大而减小;通过对两类不同的粗糙单元构成的粗糙壁面的计算分析,发现该数值模拟方法可以描述流体流经近壁面的流场特性和流场结构,并为工程实践提供一定的基础。

Other Abstract

The flow on the near-surface wall is one of the most important research topics in the field of blown sand physics and structural wind engineering. The description of the near-wall flow field structure can correctly understand and predict the behavior of the fluid, so the study of the near-wall surface flow field structure is very critical. Therefore, the research works of this article are as follows:1. This paper briefly reviews the current research status of turbulence characteristics and near-surface flow field structure of fluids flowing through the near surface by scholars at home and abroad, and summarizes and analyzes them from three aspects: theoretical research, numerical simulation and wind tunnel test;2. Aiming at the rough walls such as buildings, vegetation layers, grass squares and stone squares existing in nature, a simplified discrete rough element model is proposed for numerical analysis. It is calculated that the differential form drag coefficient reaches the maximum value when the distance and height ratio of the adjacent rough elements is 7; Through the calculation of the skin friction coefficient, the position of the flow field reattachment point is obtained, and this value is consistent with the existing results. The aerodynamic roughness length and zero-plane displacement height are calculated based on the flow resistance, and it is found that the aerodynamic roughness length reached the maximum at a distance and height ratio of 6;3. For the undulating topography and landform of sand ripples, sand dunes, etc., it is simplified as a continuous cosine function-like continuous rough element model, and numerical analysis of the rough wall surface is performed. The results show that the differential form drag coefficient decreases with the increase of the wavelength and amplitude ratio. By analyzing and calculating the skin friction coefficient on the wall surface of the wavy wall, the position of the separation point and reattachment point where the tail vortex falls behind the peak is obtained. The zero-plane displacement height and aerodynamic roughness length on a rough wall composed of continuous rough elements can be calculated from the flow resistance. Under different Reynolds number, the form drag coefficient, skin friction coefficient and zero plane displacement height decrease with increasing wind speed;Through the calculation and analysis of the rough wall composed of two kinds of different rough elements, it is found that the numerical simulation method can describe the flow field characteristics and flow field structure of the fluid flowing through the near wall surface and provide a certain basis for engineering practice.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226551
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
王鹏. 二维粗糙壁面上湍流流动特性的数值模拟[D]. 兰州. 兰州大学,2018.
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