Oscillating grids are frequently used with water and Newtonian fluids to generate controlled turbulence and mixing. Yet, their use with shear thinning fluids still requires experimental characterization. Proper orthogonal decomposition (POD) is applied to PIV measurements of the flow generated by an oscillating grid in water and a shear thinning dilute polymer solution (DPS) of xanthan gum. The aims are to investigate the ability of POD to isolate periodic flow structures, and to use it to describe the effects of the shear thinning property. A dominance of the low order POD modes is evidenced in DPS. The methods applied in blade stirred tanks to identify oscillatory motion fail here. However, a strong mode coupling in the grid swept region is observed, determined by the working fluid and by an underlying chaotic nature of the flow. Possibilities of reconstructing turbulence properties using high order modes are discussed.

中文翻译：

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水和剪切稀化聚合物溶液中振荡网格湍流的POD分析

振荡栅格经常与水和牛顿流体一起使用，以产生受控的湍流和混合。然而，它们与剪切稀化液一起使用仍需要实验表征。适当的正交分解（POD）应用于水中振荡网格和黄原胶剪切稀稀聚合物溶液（DPS）产生的流动的PIV测量。目的是研究POD隔离周期性流动结构的能力，并用它来描述剪切稀化特性的影响。在DPS中证明了低阶POD模式的优势。叶片搅拌罐中用于识别振荡运动的方法在此失败。然而，观察到在网格扫掠区域中的强模式耦合，这取决于工作流体和流的基本混沌特性。