Numerical Simulation And Reduced Order Modeling Of Valveless-micropump Involving Multi-physics Coupling

As one of the most important micro-fluid power sources of micro-electro-mechanical system, valveless micropump has a very broad application prospects in many different fields. To predict the performance of micropump is very important and necessary in the process of reasch and development. However, conventional experiment tests are impossible to investigate the micropump specific characteristics before the prototyping, and it's difficult to study the inside flow characteristic of micropump, and only the ouput volume flow rate and pressure are studied. To research the micropump mechanism and provide the design criteria for structural design, the inside flow characteristics of micropump have to be studied. The key to future development of miropump is whether the R&D prototype can be successfully used to realize industrialization, which largely depends on how effectively the computer simulation technology applied to the design of micropump. Therefore, in this paper, the electrostatic micropump involving electrostatic-structure-fluid three physics coupling is investigated based on numerical simulation and reduced order model (ROM), mainly including the following aspects:1. The characteristics of micro-fluid are simply introduced, the scrope of macro-fluid theory is given, the directional transmission fluid function of valveless micropump is theoretically confirmed, and the output flow rate equation is derived. In addition, finite element analysis software ANSYS/Flotran is used to simulate the fluid flow in nozzle and diffuser.2. The theory of liquid-solid coupling system is simply introduced, classification and characteristics of liquid-solid coupling system are also given. The mass matrix of chamber fluid is added to the mass matrix of structure based on the structure dynamic equation of membrane, thereby the vibration equation of micropump liquid-solid coupling system is obtained ignoring the damping effect. In addition, finite element model of membrane-fluid coupling system is constructed by ANSYS, which is used to analyse the influence of structural dimention and fluid pressure on the wet modes.3. The ROM of electrostatically actuated membrane is constructed based on numerical calculation and mode superposition method, the ROM is used to simulate the static and dynamic characteristics of electrostatically actuated membrane, and the effects of different parameters such as residual stress, initial gap, diaphragm radius, diaphragm thickness on pull-in voltage and pull-in position are also investigated by the ROM. In addition, based on parameters calculated by FEM, by adding nonlinear comparison and switch module in Matlab/Simulink, the simulation functions of ROM are improved, so dynamic pull-in and release process of electrostatic membrane is accurately simulated.4. The full coupled model (FCM) of vaveless electrostatic micropump is constructed using computational fluid dynamics software CFD-ACE+, the interactions of electrostatic-structure-fluid three physics are taken into account in the FCM, which is used to investigate the dynamic pull-in phenonmen of electrostatic micropump, and the inside information of micropump is obtained by simulations, and the characteristics of micropump under different driving frequencies and back pressure are also investigated. In addition, the defined boundary model (DBM) of micropump is established according to the provided information of existing literatures, so that the complicated three physics coupling problem is simplified into a fluid flow problem. By comparing of FCM with DBM, it shows that DBM can be conducted easily with lower cost but have a poor precision and result in distorting characteristics, the FCM can predict the transient behaviors of the micropump very well since the electro-mechanical and liquid-solid interactions are all considered, but the computational cost is much larger.