中文摘要：

对不同水平剪切强度下受限空间内热分层流的流场进行了PIV测量。应用特征正交分解（POD）方法分析了受限空间内热分层流的流场结构。结果表明，没有水平强迫气流时，低阶POD模态占总能量的比重较高，表明水平方向的宏观流动为主流运动；水平强迫剪切气流会造成能量向高阶POD模态耗散转移。而且，水平强迫剪切气流造成不同阶数的POD模态中竖向动能与水平方向动能的比值均比没有水平强迫气流时高，表明水平强迫剪切气流降低热分层流的稳定性并促进竖向质量交换。

英文摘要：

PIV measurements are carried out on the thermally stratified flows under different horizontal shear intensities in a confined space. Proper orthogonal decomposition （POD） is used to analyze the structures of these thermally stratified flows. Results show that, at the conditions without forced horizontal airflow, the low-order POD mode constitutes a high proportion of the total energy of the flow, and the horizontal flow is the dominant flow structure. The horizontal shear drives the energy to dissipate from large structure to smaller structures. Relative to the conditions without forced horizontal airflow, the ratios of vertical kinetie energy to horizontal kinetie energy become higher for eaeh order of POD mode in the conditions with forced horizontal airflow. This indicates that horizontal shear can result in stratification instability and enhance the mass exchange in the vertical direction.