斜坡流动分离数据同化和多工况泛化研究

Study on Data Assimilation and Multi-condition Generalization of Slope Flow Separation

为准确预测不同倾角斜坡面上的流场特性,该文采用集合卡尔曼滤波方法对剪切应力输运模型常数进行数据同化的优化,得到一套适用于多工况参数下的流场计算预测方案。首先,利用粒子图像测速法对高、中和低三组不同坡度的斜坡模型在雷诺数Re=38100、Re=57200和Re=85800下的分离流动进行了实验测量,以测得的若干下游位置处时均流向速度分布作数据同化的实验观测,分析了单模型工况下,不同位置处的观测数据对流场同化的影响。随后,该文以中坡度中等雷诺数下的同化模型常数对其他坡度和雷诺数下的流场进行了拓展计算,分析并验证了该数据同化模型在多工况参数下的泛化能力。研究表明:在不同坡度和雷诺数下,中坡度Re=57200条件下同化获得的模型常数对坡度和雷诺数泛化的效果最好,可认为该套模型常数适用于该文研究的所有工况和参数;相较于原始模型,同化后流场的涡黏分布主要集中在斜坡中下游位置,泛化后再计算发现在坡面的中下游位置涡流黏度分布整体上小于原始模型常数计算结果。

The Ensemble Kalman Filter method is used to optimize the data assimilation of the shear stress transport model constants to accurately predict the characteristics of the flow field on the slope surface with different inclination angles.A set of flow field calculation and prediction scheme is obtained under multiple working conditions.To this end,particle image velocimetry is applied to measure the separation flow of slope models with high,middle and low gradients at Reynolds number Re=38100,Re=57200 and Re=85800.The measured time-averaged velocity distribution at several downstream locations is used for data assimilation.The influence of observed data at different locations on flow field of a single model is analyzed.In this paper,the model constant of assimilation at medium slope and Re is extended to calculate the flow field at other slopes and Reynolds numbers.The generalization ability of the model augmented by data assimilation under multi-condition parameters is analyzed and verified.The results show that the model constant obtained by assimilation under medium gradient and Re=57200 is most suitable for generalization compared with other gradients and Reynolds numbers.It can be considered that this set of model constants is suitable for all conditions and parameters studied in this paper.At the same time,compared with the original model,the eddy viscosity distribution of the assimilated flow field is mainly concentrated in the middle and downstream of the slope.The generalized calculation shows that the eddy viscosity distribution in the middle and downstream of the slope is lower than that of the calculation result of the default model.