圆柱以及圆柱群一直是钝体绕流研究中最为典型的课题,本文在文献中已有研究成果的基础上,采用对双圆柱同时进行同步测压的方法,在串列、并列和斜置三种典型排列方式以及不同间距下,对双圆柱绕流问题——特别是脉动气动力的特性——进行了实验研究。 为了完成本实验,首先开发了一套32通道同步压力测量系统,标定了各个通道的频响特性,编制了对传压管道造成的信号畸变进行反演修正的程序。通过对单圆柱绕流进行同步测压,并和文献中的结果进行对比,验证了本套同步测压系统的可靠性。 在同步测压的基础上,本文主要研究了双圆柱绕流以下几个方面的问题: 1.表面压力分布的时均和脉动特性; 2.气动力的时均和脉动特性; 3.利用功率谱分析气动力脉动频率和旋涡脱落之间的关系; 4.两个圆柱之间脉动升力的相关分析和相位关系; 5.两个圆柱之间分离点压力的相关分析和相位关系; 6.分离点脉动压力和圆柱周向压力分布的相关情况,以及脉动气动力和周向压力分布的相关情况; 7.瞬时压力分布; 8.利用概率密度分布函数分析脉动气动力的统计特征。 本文的实验结果再次证实了双圆柱绕流的流态会在某些间距上出现突变,而在这些临界间距之间,流态则保持相对的稳定。在串列、并列、斜置三种排列方式下,气动力的最强脉动都出现在两圆柱的间距稍大于各自临界间距的位置。通过对脉动气动力和脉动压力之间的相关分析发现,可以采用某些特殊位置测点的脉动压力来表征脉动气动力。
电加热器
Flow around single circular cylinder and grouped circular cylinders is the most typical problem which is paid much attention in the research of blunt body flow. In this paper, based on the existing research in the literatures, flow interference between two circular cylinders in three representative arrangements(in tandem, side-by-side and staggered)—especially the characteristics of fluctuating aerodynamic forces—was investigated experimentally by simultaneous multi-pressure measurement.In present experiment, a 32-channel simultaneous multi-pressure measurement system was developed and the dynamic characteristics of each channel which were used in the program of the correction for distorted pressure signals through the pressure transfer pipe were calibrated. The reliability of the system was verified by measuring the fluctuating pressure distribution of single circular cylinder and comparing the results with those in the literatures.Based on the results of the measurements of fluctuating pressure distribution, the following aspects of flow around two circular cylinders were carefully studied:1. The characteristics of mean and fluctuating surface pressure distribution;2. The characteristics of mean and fluctuating aerodynamic forces;3. The relationship between the frequencies of fluctuating aerodynamic forces and vortex shedding by the power spectrum analysis;4. The correlation between the fluctuating aerodynamic forces of two circular cylinders;5. The correlation between the fluctuating pressure at separation point of two circular cylinders;6. The correlation between fluctuating pressure at separation point and those around the whole circumference, and the correlation between fluctuating aerodynamic forces and fluctuating pressure around the whole circumference;7. The instantaneous pressure distribution;8. The statistical characteristics of the fluctuating aerodynamic forces analysed by PDF(probability distribution function).The jump between different flow patterns at certain critical position was discovered again in present experiment, and the flow patterns were relatively steady between the critical positions. In the three arrangements, the maximum of the fluctuating aerodynamic forces all appeared at the position when the distance between the two circular cylinders was appreciably longer than critical value. The correlation analysis of the fluctuating aerodynamic forces and the fluctuating pressure distribution showed that the fluctuating aerodynamic forces can be expressed by the fluctuating pressure at special positions.