Numerical Simulation on Laminar-Turbulent Flow around Fish-Like Advancing Wing

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Unsteady viscous flow field around a fish-like advancing NACA wing is numerically studied. The main objective is to study the abilities of a deforming body to produce thrust and achieve higher propulsive efficiency in viscous flow field. The Reynolds numbers based on the oncoming velocity and the body length range from 10^3 to 10^6. The flow is simulated by solving two-dimensional unsteady Navier-Stokes equation in a primitive value formulation, while the eddy-viscosity is described by algebraic model and transitional zone is computed by empirical formula. The numerical scheme is based on the MAC method where the Navier-Stokes equation is solved by the time marching method on a body fitted coordinate system. The simulation shows that pressure is acting as thrusting force while frictional force is acting as resistance during the undulating motion. Thrust goes up with the increase of phase velocity of undulating wave. In the case of laminar flow, the frictional force enlarges with the increase of phase velocity. While in the case of turbulent flow, the increase of phase velocity can suppress turbulence accompanying with the decrease of frictional force. Two vortices shed from the trailing edge during one undulating period. The vortex shedding forms are different between laminar and turbulent cases. The propulsive efficiency depends on Reynolds number and body thickness. The variation of undulating start-point also slightly affects propulsive efficiency and frictional force.
2002-03-20

Numerical Simulation on Laminar-Turbulent Flow around Fish-Like Advancing Wing

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