基于POD方法的合成双射流流场模态分析

Modal analysis of dual syntehtic jets based on POD method

为更深入地了解合成双射流自身的流场特性,开展了PIV实验研究,分析了一个周期内流场涡结构的演化特征,对实验数据进行了本征正交分解(POD)模态分析,详细分析了各阶模态所表征的流动结构、时间系数及其频谱特征。结果表明,合成双射流激励器的两个腔体交替压缩形成两股相位差180°、相互卷积吸引的旋涡对,能量效率和工作频率倍增;前四阶POD模态占据了流场80.5%的能量,对应的时间系数的频率分别为激励器的工作频率和二阶谐频;POD前两阶横向模态呈对称分布,后两阶呈反对称分布;而前两阶流向模态则呈反对称分布,后两阶呈对称分布,反映了合成双射流流场的对称性特征。

In order to understand the flow field characteristics of dual synthetic jets more deeply,particle image velocimetry(PIV)experiments were conducted.The temporal and spatial evolution of vortex structures in one cycle were analyzed.Proper orthogonal decomposition(POD)method was adopted.Flow structures,time coefficients,and power spectra of the first four modes were analyzed in detail.It was found that two cavities of the actuator were mutually compressed to form two strands of synthetic jet with a phase difference of 180°.Thus the energy efficiency and working frequency were doubly increased.The first four POD modes occupied 80.5%of the energy,and the frequencies of corresponding time coefficients were the working frequency and its second-order harmonic frequency,respectively.The first two POD transverse modes were symmetrically distributed and the third and fourth modes were anti-symmetrically distributed,while for the streamwise modes,the facts were just the opposite.This reflect the symmetrical characteristics of the dual synthetic jets’flow fields.