Research On Multiple Working Conditions Of Hydrofoil Based On The Panel Method

Hydrodynamic analysis of a steady flow passing over a hydrofoil is a basic problem for applications of fin stabilizer and biomimetic pusher.And also,the free surface simulation between two phases has always attracted scholars’ interests.In this paper,the hydrodynamic analysis of a steady surface flow passing over two foils is described and we expect to descend the double-foil’s wave or increase the hydrofoil lifting.The numerical model for hydrofoil flow is established based on the potential flow theory.Two vortex sheets are placed along the hydrofoils’ chord to produce the expected lift.Different boundary conditions are imposed on the boundaries of the fluid domain respectively.Finally,to enclose the algebraic matrix equation,we use the velocity based Kutta condition at the trailing edgesThen,the convergence studies relative to mesh and time step are performed.The lifting coefficients and free surface waves both converge considering the factors mentioned above.Some cases are performed based on the linear and nonlinear free surface conditions to have a comparison with the experiments.Both of them have a good conformity on the lifting coefficient and surface wave.And some conclusions are attained considering different hydrofoil depths.The numerical model for flapping foils is built in chapter 5 considering the wake vortex shedding.The core of the numerical model is the rule of circulation preserving,besides the potential flow theory,the boundary element method and the airfoil theory.In this paper,the wake vortex moves as the velocity of the fluid particle where it occupies.Three main factors making sense to the hydrodynamic performance of the flapping foil,the maximum nominal angle of attack,the Strouhal number and the heave amplitude-to-chord ratio,are discussed in this paper.In the analysis of hydrodynamic interference of two foils,four factors are discussed,they are the angles of two foils,the horizontal and the vertical distances between the foils.It could be found that,the waves inspired by the foils’ interference would be weakened if a correct combination of angles is selected.Foil B is totally in the wake of foil A when the two foils are horizontally aligned.And some interesting conclusions can be drew under this circumstance.