A study on flow physics of burst-and-coast swimming of koi carp (Cyprinus carpio koi) based on measurements and numerical simulations

Abstract

Burst-and-coast, as a locomotion type in freely routine swimming of koi carps (Cyprinus carpio koi) was studied, using a novel integrated CFD method solving the body-fluid interaction problem. The numerical simulation was incorporated with the tracking experiment. The two burst modes, MT (Multiple Tailbeat) and HT (Half Tail-beat) were investigated. The body locomotion was predicted and the flow physics was visualized, both in good agreement with the corresponding experiments. The energy cost and several critical control mechanisms in burst-and-coast swimming of koi carps are explored. Results on the energetics show that, burst-and-coast swimming does not actually save energy comparing with steady swimming at the same average speed, in that frequently changing of speed leads to decrease of efficiency. Index Terms-burst-and-coast swimming, CFD (computational fluid dynamics), fluid-body interaction, self-propelled swimming, Cyprinus carpio koi I.

The Kinematics and Dynamics of Schizopygopsis malacanthus Swimming during Ucrit Testing

“…The values (Equation (5)) for steady and unsteady modes at each flow gradient in this investigation were the same because the Reynolds number was calculated (Equation (7)) using the same flow velocity and fish length for both modes and there is no energy-saving coast phase. We conclude that the axial force and energy consumption are greater in the unsteady swimming mode than in the steady mode, consistent with the analysis of Yang et al [ 13 ] and Wise et al [ 30 ].…”

“…Due to the software’s processing capability and the huge amount of data needed for microscopic analysis, video clips of the middle 20 s at each flow velocity increment were analyzed frame by frame using the motion tracking software Etho Vision XT 9.0 [ 15 ]. The results of other time periods are comparable to this results, and as per the study dynamics of Wu et al [ 12 ], Yang et al [ 13 ], and Ashraf et al [ 16 ], only the data in a period of 0.4 s, 0.4 s, 10 s were analyzed. The center-of-mass co-ordinates of fish were obtained at 1/30-s intervals, and the instantaneous displacement, instantaneous ground velocity, and instantaneous acceleration at 1/30-s intervals were calculated from the change in co-ordinates.…”

“…Wu et al [ 12 ] used particle image velocimetry (PIV) to reveal the kinematic characteristics and wake patterns of carp burst-coast swimming in an open tank with still water, concluding that burst-coast motion saves 45% of energy compared to steady swimming. However, Yang et al [ 13 ] found that when the water velocity in an open tank exceeds 0.34 m/s, burst-coast swimming does not reduce energy consumption. We observed similar gait changes during the test, and with the development of new animal behavior observation techniques, a more detailed and quantitative study of fish swimming behavior is now possible.…”