大跨度柱面屋盖气动特性雷诺数效应研究

发布时间：2018-07-05 15:46

本文选题：柱面屋盖 + 雷诺数效应　；参考：《哈尔滨工业大学》2015年博士论文

【摘要】：雷诺数效应一直是建筑工程抗风研究中的重要基础性问题。近年来,各种造型新颖的大跨度屋盖结构不断涌现,随着屋盖跨度的增加和质量轻型化,抗风设计要求更为精细化,越来越多的学者开始关注大跨度屋盖的雷诺数效应。众所周知,对于曲面屋盖结构,其气动参数随雷诺数变化显著,但至今尚无系统研究这种雷诺数效应的影响。大跨度屋盖结构大都处于大气边界层底层,其周围气流的绕流模式较为复杂,影响建筑雷诺数效应的因素诸多,主要包括屋盖几何特征、表面粗糙度和近地面高湍流度三个方面。本文基于经典圆柱绕流的风洞试验,验证了试验方法的正确性,并探讨了表征雷诺数效应的关键气动参数及相应的识别方法;以大跨柱面屋盖为研究对象,采用风洞试验的方法重点探讨了不同几何特征(包括长宽比、矢跨比)、来流湍流和表面粗糙度对柱面屋盖雷诺数效应的影响;在此基础上,提出了考虑雷诺数效应的风荷载估计方法,为今后的相关研究方向提供一些建议。本文主要开展了以下几个方面的工作:(1)雷诺数效应在形式上表现为不同雷诺数条件下流动状态、边界层分离和旋涡作用的差异,进而直接影响气动参数,因而反过来从风洞测压试验获得的气动参数信息可以用于再挖掘流场特点。基于此,本文提出结合模型表面风压分布来识别流动转捩与边界层分离的方法,利用谱正交分解法来识别旋涡作用,通过分析不同雷诺数下主导旋涡的作用特点,并定量评估其对脉动风压场的能量贡献,为结构抗风设计提供参考。(2)柱面屋盖与圆柱的差异主要体现在壁面边界的影响上,为探究其影响规律,通过在圆柱前后设置导流板的方式模拟了柱面屋盖的边界条件。研究发现,前导流板的主要作用是通过增加来流湍流度促使分离边界层提前转捩,后导流板则抑制了尾流中的旋涡脱落。研究揭示了由于壁面边界的存在,使得来流中产生附加湍流,这是造成柱面屋盖与经典圆柱雷诺数效应差异的根本原因。(3)几何特征是影响柱面屋盖雷诺数效应的主要因素。针对不同长宽比和矢跨比柱面屋盖的雷诺数效应展开系统的风洞试验研究,通过分析模型气动参数随雷诺数的变化规律,获得转捩区间大致在6.9×104~4.14×105范围内,研究表明屋盖长宽比的减小会推迟分离边界层由层流向湍流的过渡,而矢跨比减小的影响则呈相反的变化趋势。(4)在利用格栅建立的不同湍流度均匀流场中对柱面屋盖进行变雷诺数测压试验。研究表明,来流湍流对雷诺数效应的影响需要从湍流度和积分尺度两方面进行考察,流场湍流度的增加会促使分离边界层提前转捩,而湍流积分尺度主要对脉动风荷载的雷诺数效应存在显著影响,在雷诺数和湍流度相同的情况下,小积分尺度湍流旋涡(0.18≤Lx/D≤0.33)更容易渗入到表面边界层和分离剪切流中,进而增加屋盖顶面和尾流区的风压脉动;系统研究了表面粗糙度(相对粗糙度ks/D=3.0×10-4~7.5×10-4)对柱面屋盖雷诺数效应的影响,增加表面粗糙度使得转捩区间向低雷诺数区域平移,但值得注意的是升力系数值明显减小,因此采用增加表面粗糙度来模拟高雷诺数的气动特性时,需要对测量数值进一步修正,有待于更深入研究。(5)针对平均风荷载,基于理想流体势流理论,建立了考虑雷诺数效应的风压系数模型,适用于不同矢跨比柱面与球面屋盖,同时结合风洞试验数据,还给出了考虑湍流度和矢跨比的风力系数模型;针对脉动风荷载,基于模糊神经网络技术,建立了大跨柱面屋盖考虑雷诺数效应的脉动风荷载预测模型,可作为围护结构抗风设计的有效辅助手段。
[Abstract]:Reynolds number effect has always been an important basic problem in the study of wind resistance in construction engineering. In recent years, various novel large span roof structures have emerged continuously. With the increase of roof span and light quality, the demand for wind resistance design is more refined. More and more scholars begin to pay attention to the Reynolds number effect of large span roofs. It is known that the aerodynamic parameters vary significantly with Reynolds number for a curved roof structure, but there is no systematic study of the effect of Reynolds number. The large span roof structures are mostly in the bottom of the atmospheric boundary layer, and the flow pattern around the air flow around it is more complex, and many factors affecting the Reynolds number effect, mainly including the roof geometric characteristics, Three aspects of surface roughness and high turbulence in the near ground. Based on the wind tunnel test of classical cylinder flow, the correctness of the test method is verified, and the key aerodynamic parameters and the corresponding identification methods are discussed. What characteristics (including length width ratio, sagittal span ratio), flow turbulence and surface roughness influence the Reynolds number effect of cylindrical roof; on this basis, a method of estimating wind load with Reynolds number effect is proposed, and some suggestions for future research direction are provided. The following work is carried out in this paper: (1) Reynolds number effect is in the following aspects In the form of different Reynolds number, the flow state, the boundary layer separation and the difference of vortex action are directly affected by the aerodynamic parameters. Therefore, the aerodynamic parameters obtained from the wind tunnel pressure test can be used to remine the characteristics of the flow field. Based on this, this paper proposes to identify the flow transition and the flow transition in combination with the model surface wind pressure distribution. The method of boundary layer separation, using the spectral orthogonal decomposition method to identify the vortex action, by analyzing the characteristics of the leading vortex under different Reynolds numbers, and quantifying its energy contribution to the fluctuating wind pressure field, provides reference for the design of the wind resistant structure. (2) the difference between the cylindrical roof and the cylinder is mainly reflected on the effect of the wall boundary. It is found that the main function of the front guide plate is to promote the transition of the boundary layer in advance by increasing the flow turbulence. The study reveals that the boundary of the wall exists because of the existence of the wall boundary. The fundamental reason for the difference between the cylindrical roof and the Reynolds number effect of the classical cylinder is caused by the additional turbulence in the derived flow. (3) the geometric characteristics are the main factors affecting the Reynolds number effect of the cylindrical roof. The wind tunnel test for the Reynolds number effect of the different length width ratio and the column roof roof is analyzed by the analysis of the model aerodynamic parameters. As the number of Reynolds number changes, the transition interval is roughly within the range of 6.9 x 104~4.14 x 105. The study shows that the decrease of the length and width of the roof will delay the transition from layer to turbulence, while the effect of the decrease of the vector span ratio is the opposite trend. (4) in the uniform flow field of different turbulence intensity, the cylindrical house is used in the use of grid. The study shows that the influence of the flow turbulence on the Reynolds number effect needs to be investigated from two aspects of the turbulent flow and the integral scale. The increase of the turbulent flow in the flow field will lead to the transition of the boundary layer in advance, while the integral scale of the turbulent flow has a significant influence on the Reynolds number effect of the fluctuating wind load, and the Reynolds number and the Reynolds number are significant. In the case of the same turbulence, the small integral scale turbulence vortex (0.18 < < Lx/D < 0.33) is more easily infiltrated into the surface boundary layer and the separation shear flow, and then increases the wind pressure fluctuation in the roof top surface and the wake region. The influence of the surface roughness (relative roughness of ks/D=3.0 x 10-4~ 7.5 x 10-4) on the Reynolds number effect of the cylindrical roof is studied. The surface roughness makes the transition interval shift to the low Reynolds number region, but it is worth noticing that the lift system value decreases obviously. Therefore, when the aerodynamic characteristics of high Reynolds number are simulated by increasing the surface roughness, it is necessary to further modify the measurement value. (5) for the average wind load, the ideal fluid potential flow theory is based on the mean wind load. In addition, a wind pressure coefficient model considering Reynolds number effect is established. It is suitable for different vertical and spherical surface and spherical roof. At the same time, combined with wind tunnel test data, the wind coefficient model considering turbulence intensity and vector span ratio is given. Based on the fuzzy neural network technique, a large span cylindrical roof is established to consider Reynolds number effect. The prediction model of fluctuating wind load can be used as an effective auxiliary method for wind resistant design of retaining structures.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU311.3

【参考文献】