Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS）...Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS） equations with a moving adaptive mesh. The effect of swimming speed, flapping amplitude, frequency and flexure amplitude on the propulsion performance of the rigid and flexible tuna-tails are investigated. Computational results reveal that a pair of leading edge vortices develop along the tail surface as it undergoes an oscillating motion. The propulsive efficiency has a strong correlation with various locomotive parameters. Peak propulsive efficiency can be obtained by adjusting these parameters. Particularly, when input power coeffcient is less than 2.8, the rigid tail generates larger thrust force and higher propulsive efficiency than flexible tail. However, when input power coefficient is larger than 2.8, flexible tail is superior to rigid tail.展开更多
The viscous flow field around two-dimensional flapping （ heaving and pitching） foils was numerically computed. The structural characteristics of caudal vortices were investigated and the contour curves at different ...The viscous flow field around two-dimensional flapping （ heaving and pitching） foils was numerically computed. The structural characteristics of caudal vortices were investigated and the contour curves at different phase angles were obtained. The relationships between the structural characteristics of the vortices and the force acting on the foil and between the widths of the caudal vortex street and of the caudal flow field were analyzed. A method to determine the shedding frequency of the vortices was proposed.展开更多
Experimental study and theoretical research were described in the paper on the characteristics of the flow field around a vertical circular cylindrical artificial island under the . action of waves and viscous curren...Experimental study and theoretical research were described in the paper on the characteristics of the flow field around a vertical circular cylindrical artificial island under the . action of waves and viscous current. Flow field and hydrodynamic coefficientS of an artificial island under the action of waves and viscous current were computed and compared with those for the cases of pure viscous current and pure incident waves and those of measured resultS with good agreement.展开更多
文摘Numerical study on the unsteady hydrodynamic characteristics of oscillating rigid and flexible tuna-tails in viscous flow-field is performed. Investigations are conducted using Reynolds-Averaged Navier-Stokes （RANS） equations with a moving adaptive mesh. The effect of swimming speed, flapping amplitude, frequency and flexure amplitude on the propulsion performance of the rigid and flexible tuna-tails are investigated. Computational results reveal that a pair of leading edge vortices develop along the tail surface as it undergoes an oscillating motion. The propulsive efficiency has a strong correlation with various locomotive parameters. Peak propulsive efficiency can be obtained by adjusting these parameters. Particularly, when input power coeffcient is less than 2.8, the rigid tail generates larger thrust force and higher propulsive efficiency than flexible tail. However, when input power coefficient is larger than 2.8, flexible tail is superior to rigid tail.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2007AA11Z250)National Natural Science Foundation of China(Grant Nos.50779033,50909079)
文摘The viscous flow field around two-dimensional flapping （ heaving and pitching） foils was numerically computed. The structural characteristics of caudal vortices were investigated and the contour curves at different phase angles were obtained. The relationships between the structural characteristics of the vortices and the force acting on the foil and between the widths of the caudal vortex street and of the caudal flow field were analyzed. A method to determine the shedding frequency of the vortices was proposed.
文摘Experimental study and theoretical research were described in the paper on the characteristics of the flow field around a vertical circular cylindrical artificial island under the . action of waves and viscous current. Flow field and hydrodynamic coefficientS of an artificial island under the action of waves and viscous current were computed and compared with those for the cases of pure viscous current and pure incident waves and those of measured resultS with good agreement.
