Finite Element Analysis Of Ultrasonic Traveling Wave Micro-fluid Driving Annular And Cylinder Model

With the extensive application of Micro-electromechanical System (MEMS) in the domain of BME, fluid driving and controlling technique has become one of the research hotspots of MEMS technique. Ultrasonic traveling wave micro-fluid driving technique is different from the present ones in principle. The ultrasonic vibration, generated by the anti-piezoelectric effect of piezoelectric ceramics, excites the traveling wave on the bottom surface of the micro-channel, and generates acoustic field simultaneously. The fluid medium in the micro-channel moves along the direction of traveling wave in the cooperated effect of acoustic streaming and acoustic radiation pressure. As a new micro-fluid driving technique, ultrasonic traveling wave driving technique has several advantages for extensive application in the future, such as non-movable components, needing lower driving voltage, convenient controlling method, fitting for miniaturization and so on.Firstly, the dissertation summarizes the development of MEMS and micro-fluid, and makes an introduction of the present kinds of micro-fluid driving and control technique. The anti-piezoelectric effect, material character and frequency character of piezoelectric ceramics are introduced. The synthesis of traveling wave is analyzed in detail. Through the study on the mechanism of acoustic radiation pressure and acoustic streaming, the relationship between driving mechanism and model parameters is obtained, which is the basic theory of the ultrasonic traveling wave driving technique.Secondly, the theory of ultrasonic traveling wave driving finite element analysis (FEA) method is introduced. The piezoelectric ceramic FE model is built based on FE method. The coupling field analysis, modal analysis theory and harmonic response analysis theory are introduced. And the basic equations of ideal medium, acoustic wave FEA theory and the acoustic-structure coupling theory are expatiated.Thirdly, the annular driving model is built by using finite element analysis software ANSYS. By the modal analysis, the nature frequencies and vibration modes are obtained, and the relationship between model natural frequencies and elastic body structural parameters, such as the inner radius, outer radius, elastic body thickness and piezoelectric ceramic thickness, is discussed. By the harmonic response analysis, the desired vibration mode is excited and the frequency characteristic is identified. The displacement variety along with the frequency and the comparison among three modes are obtained. These offer the guidance for model structure design. The acoustic-structure modal analysis is carried by ANSYS software with numerical method. The effect of acoustic field on model natural frequency is obtained by comparing the coupling model with the uncoupling model. The vibrancy range and the acoustic pressure distribution of B(0,5) mode are compared through the harmonic response analysis.Finally, the ultrasonic traveling wave driving cylinder model is built. The desired modes and natural frequencies are obtained by modal analysis. Filling fluid material in the cylinder model, the vibration, natural frequency and acoustic pressure of different modes are gained through acoustic-structure coupling analysis. The relationship between the acoustic pressure distribution and the displacement distribution is analyzed, and the effect on the natural frequency of different fluid, such as water and air, is also obtained. Choosing air as the fluid medium, the fluid-structure coupling model and the analysis steps are introduced. The velocity streaming figure and the velocity contour figure are gained to analyze the flow status. These offer guidance and reference for analysis of micro-fluid movement, mixture and model structure optimization.