【作者】 李中华；

【导师】 肖仪清；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2014， 硕士

【摘要】 大涡模拟是计算风工程中的重要研究方法和手段，能够比较准确的模拟脉动风。在大涡模拟中脉动入口边界条件尤为重要，生成脉动风入口的方法有很多，其中随机序列合成法应用广泛。然而随机序列合成法中的DSRFG方法由于脉动成分的加入导致平均风剖面变化，模拟的风场达不到预想效果。大涡模拟中网格对计算域中风场存在过滤，在入口处生成的脉动速度存在的最高频率应该与计算域中过滤的截断频率相统一，减少计算域中不可分辨频率对计算的影响。随机序列合成法中的DSRFG方法还存在较为明显的压力梯度问题。本文有以下主要研究内容：基于von-Karman谱推导出大涡模拟中网格尺寸与截断频率之间的关系，并用具体公式描述其关系，保证程序中脉动成分的时间过滤和计算域中的空间过滤相统一，减少高频成分对计算结果的影响。计算多个FLUENT模型，分析每个计算模型870个检测点处的脉动风速。使用曲线拟合和曲线拟合优度检验理论找出最能够代表计算域内平均风速的风剖面，分析DSRFG方法程序中给定平均风剖面与计算域中平均风剖面的差异，通过修改原有DSRFG程序使计算域中平均风剖面满足规范要求。在MATLAB中分析每一个CASE870个检测点处的脉动风速，对比RFG方法和DSRFG方法脉动风功率在计算域中的变化，以及湍流强度在计算域中的变化情况，并分析过滤高频成分对DSRFG方法脉动特性的影响。将DSRFG方法的原有程序改编成MATLAB可识别的语言，并通过MATLAB生成脉动速度，通过MATLAB过滤掉脉动速度的高频成分，将处理后的速度重新加入FLUENT中，用以减弱DSRFG方法存在的严重压力梯度问题。更多还原

【Abstract】 Large eddy simulation is an important method in computational windengineering and can simulate fluctuating wind accurately, in which the boundaryconditions of pulsating inlet is particularly important. There are many means tocreate the pulsating inlet, of which the random sequence synthesis is very popular.However the DSRFG method of random sequence synthesis can’t simulate thereal wind field well, as the average wind profile changed with the ripplecomponent. In the LES, the highest frequency of fluctuation velocity created inthe pulsating inlet should be in accordance with the cut-off frequency filtered inthe computational domain, to reduce the affection of the frequency indiscernible.Meanwhile, the DSRFG method has some distinct poblems with pressuregradient. To solve the problems above, work of this paper is as follows:The relationship between grid size and chopping frequency is deduced andthen exhibited with specific formula on the basis of von-Karman spectrum,assuring the coherence between time filtration of ripple component and spacefiltration in computational domain, reducing the affection of high frequency.The fluctuating velocity of870point is analyzed in each case. The mostfitting curve of wind should be found in computation domain, in which,polynomial curve fitting law and goodness of fit test is used. Finally, the way ofchecking the changing regular of wind profile be found in computational domainto promise the wind profile be legal.The fluctuating wind velocity of870points in computational domain isanayzed in Matlab, comparing the changing of fluctuating wind power andturbulence intensity in conputational domain with methods of RFG and DSRFG.DSRFG programs were changed to the language identified in MATLAB togenerate wind pulsation. The pulsation is filtered by MATLAB, finally filteredwind were used in FLUENT to reduce the problem of serious pressure gradient.更多还原