Identification of Bluff Body Wake Characteristics Based on a Soap Film Water Tunnel

Flow around structures is a common phenomenon in practical engineering. When faced with complex flow conditions, the wake structures formed by structures falling off are relatively complex and diverse. To analyze the flow field structure and characteristics of the flow around the rotating structure, this paper utilizes an experimental device called a soap film water tunnel to investigate the hydrodynamic flow characteristics around the rotating cylinder. First, a vertical soap film experimental device was constructed, and the optical interference method was employed to visualize the wake of the structure. The experiment mainly studies the wake structure of the flow around a rotating cylinder at various relative rotation speeds. It was found that as the relative speed α gradually increases, the shedding wake structure of the rotating cylinder will exhibit three types sequentially: vortex shedding zone, stable zone, and unilateral vortex zone (secondary unstable zone). Finally, the flow field structure generated by the rotating cylinder was analyzed and reconstructed using the Proper Orthogonal Decomposition (POD) method. This analysis revealed a trend where small-scale structures in the wake are progressively captured as the mode number increases. It shows that the POD method can effectively analyze the evolving pattern of the wake structure.