Research On Drag Reduction Using Piezoelectric Vibration Based On Moving Body Surface In The Fluid Fied

When objects move in water or air, drag will be generated from the fluid flow around them. The drag compose of two parts: the friction drag and the pressure drag.For these objects which shape are close to streamline, for example, those ships, the friction drag is main proportion of the drag around them. Reducing the drag around those moving bodies through some certain methods in the flow field can not only save energy, but also can improve their mobility. So, it is very meaningful to reduce the drag around the moving bodies in the flow field.Based on the piezoelectric theory, the vibration theory, the hydrodynamics and the computational fluid mechanics, the drag changes of several kinds of moving bodies which shapes are like ships are analyzed with vibration and without vibration.First of all, this paper introduces the related theories and equations of boundary layer in the fluid dynamics. I compared the coefficient of the friction drag of the laminar boundary layer and the turbulent boundary layer. And I analyzed the drag reduction principle in the high frequency of micro vibrations.Secondly, based on the knowledge of the piezoelectric theories and vibration theories, I design a piezoelectric vibrator to achieve the required wall vibrations.And the modal analysis and transient analysis are conducted through the finite element software. So the wall deformation and vibration parameters are obtained.On the basis of those analysis, the law of wall vibration is written in a program which can be embeded in the flow field analysis software. And then, simulation of the fluid-structure-electricity interactions in a single directions is established.In this paper, changes of the drag and friction drag of three kinds of models with different vertex angle are analyzed under the effects of vibrations with the method of simulation. Simulation analysis was carried out in five different flow velocities. The drag reduction rate of the corresponding model are calculated. The causes of the drag changes of different models are analyzed too. For the model with obvious drag reduction which vertex angle is 10?, further analyzes are conducted with the changes of amplitude and phase of vobration. And the reasons are analyzed too.Finally, in the experiment part, the experiment model of moving bodies are made. Piezoelectric ceramics are pasted on the wall of the experiment model and the piezoelectric vibrator is made. First, using the laser vibration measurer, the vibrations of the piezoelectric vibrator are measured. The correctness of the simulation analysis is validated. And then a test system is set up to measure the dragof the moving bodies model. Experiments are conducted in the tunnel with different flow velocities, amplitudes and phases. The results of drag changes are basically in agreement with the experimental simulation results, the correctness of the simulation analysis is verified.