Investigation On Electromagnetic Control Of Flow Around A Hydrofoil

Lorentz force can be generated by the electrodes and permanent magnets coated on the hydrofoil when they are placed in the weak-conducting electrolytic solution. The structure of the flow field around the hydrofoil can be changed when the hydrofoil is subjected to the Lorentz force. Therefore, the hydrodynamic characteristics of the hydrofoil can be improved, including preventing the flow separation, delaying or suppressing stall, decreasing the drag, increasing the lift, reducing noise and vibration, enhancing the stability of the flow and so on. The performance of the ship can be promoted due to these improvements, including endurance, controllability, stealth and other capabilities. Compared with the other means of flow control, electromagnetic control is highly flexible and it can affect the flow field without any contact to the fluid. Its mechanicals are also simple and reliable, so it has important research value and broad application prospects.In this thesis, after a brief review of the development of the electromagnetic control technology and the basic theory of electromagnetism and fluid mechanics, the electromagnetic control of a hydrofoil is investigated from numerical simulations and experiments. The main work is as follows:In the third chapter, the three-dimensional distribution of the Lorentz force around the hydrofoil is obtained by using the electromagnetic module of ANSYS based on the Maxwell equations, where the Lorentz force is tangential to the surface of the hydrofoil, exponential decay normal to the surface and distributed periodically in the spanwise. Then the Lorentz force data are added to the momentum equation of flow governing equation by the function of FLUENT UDF. Numerical simulations for flow around such a hydrofoil due to the Lorentz force are performed by using the detached-eddy simulation method. The effects of the electromagnetic interaction parameter and attack angle on the flow structures around the hydrofoil as well as the lift and drag coefficients are investigated.In the fourth chapter, flow visualizations of flow field of the hydrofoil with and without the electromagnetic control are carried out under Re = 6000and Re = 15000. The flow fields of the hydrofoil under the steady and dynamic control are measured using PIV. The velocity field and vortex field are obtained. Results show that the Lorentz force applied on the hydrofoil can effectively improve the flow structures around the hydrofoil, suppress its vortex and reverse flow, delay separation.