槽道非定常流场脉动特性的POD分析

针对槽道内非定常流场的脉动程度是影响传质、传热的效率问题,通过构建2DPIV测量非定常流场瞬态速度矢量场的实验系统,分析了2DPIV测量的各个时刻矢量场和涡量分布的形态,获取了非定常流场的循环周期和频率;利用本征正交分解(POD)技术分解了2DPIV的测量非定常流场的瞬态速度矢量场,根据各个模态的能量比,选取前16阶模态作为非定常流场的主导结构模态,并对POD分解的前16阶模态系数进行功率谱分析;结果表明POD分解的低阶模态分别表征了非定常流场的基频和相应的倍频,阐明了非定常流场的脉动机理;非定常流场的脉动是由于一些涡列和余弦形式的波状主流形成的,并将这些涡列以及伴随的波状主流的脉动频率映射到POD分解的低阶主导模态系数上。

Fluctuation characteristic analysis of unsteady flow field based on proper orthogonal decomposition

The fluctuations in the unsteady flow channel field can easily affect the efficiency of mass transfer and heat transfer.An experimental system is constructed to carry out 2DPIV measurement of the transient velocity vector field flow of unsteady field. With the experimental system, and the forms of vector field and vorticity distribution at each time are analyzed, and the cycle and frequency of the unsteady flow are obtained. The transient velocity vector field of unsteady flow field is decomposed using Proper Orthogonal Decomposition (POD) technology. According to the energy ratio of various modes , the first 16 modes as dominant modes are selected to represent dominant structure of unsteady flow field, and the first 16 modes coefficient of the POD decomposition are analyzed using power spectrum. The decomposition results show that the low order modes with POD are the fundamental frequency and corresponding frequency multiplication of the unsteady flow field, and the fluctuation mechanism of unsteady flow field is revealed. The fluctuation of the unsteady flow field is caused by some vortexes and cosines wave formed mainstream, the fluctuation frequency of the vortexes and wave mapping of the mainstream maps the dominant low order coefficients of POD.