In order to understand the propulsion mechanism and propulsion performance of ornamental fish in the state of turning motion,the juvenile grass golden fish(Carassius auratus)with body length of 5-8 cm was taken as the research object,and the changes of the fluid flow field of the maneuvering motion were tracked by particle im-age velocimetry(PIV)and vorticity moment theorem,and the motion characteristics and dynamic characteristics of the tail of the juvenile fish during the turning process were analyzed.The results showed that the morphological structure of the juvenile C-shaped and S+C-shaped mainly changed during the turning process,and the positive and negative vorticities of the flow field around the tail of the juvenile fish appeared alternately during the turning process.When the body morphology of the fish is C-shaped and turned,the average velocity of the juvenile is 0.130 7 m/s,and the positive force of the fluid on the tail of the juvenile fish is 2.06 mN to 133.49 mN,and the negative force is-83.85 mN to-2.15 mN.When the body morphology of the fish is S+C structure,the average velocity of the juvenile is 0.104 4 m/s,and the positive force of the fluid on the tail of the juvenile fish is 24.06 mN to 80.95 mN,and the negative force is-59.60 mN to-5.86 mN.The results show that when turning,the maneuverability of the fish body shape with C-shaped structure change is better than that of fish body shape with S+C structure change,and the time of force peak is different for different turning types.
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万方数据