Study On The Behavior Of Fluid Inside Tube Driven By The Deformation Of Tube Wall

In this paper, a two-dimensional valveless micro-pump model is studied. Valveless micro-pump can realize transport of fluid without making the use of osmotic pressure gradient or hydrostatic pressure gradient. Its design principle is very novel, the structure is relatively simple, fast response, and it is suitable for miniaturization. So it has a great application prospect. Many researchers have proposed we could use electromagnetic actuation, piezoelectric drive, gear, chemical thermal gradient, the oscillating charge and a variety of mechanical method to drive fluid flow. In our study, we use the periodic deformation of wall tube to drive the fluid. Lattice Boltzmann Method (LBM) is applied to study our model. This method is a mesoscopic fluid mechanics calculation method, which is based on the theory of molecular motion, and it studies the fluid by use of the non equilibrium statistical method. LBM is particularly suitable for simulating fluid with complex boundary and moving boundary.In this paper, according to the established two-dimensional valveless micro pump model, how the deformation of tube wall affects the fluid dynamics is analyzed, and a preliminary study on this valveless micro-pump model is carried out. In the first part, there is no pressure difference between inlet and outlet of the pipe. The influences of the frequency, the maximum depth and the position of the deformation on the average flux at outlet of tube are analyzed. The simulation results show that:(1) The average flux at outlet shows a nonlinear relationship as the driving frequency. At some resonant frequencies, the average flux reaches a peak value, and when the driving frequency exceeds a critical value(3.2Hz), the flow reversal; (2) When the deformation position is in the center of the pipe, the average flux is almost zero; The farther the deformation position away from the pipe center, the easier the directional flow is to form in the pipe, and the larger the net flow rate is; At the same time, the deformation position also has a certain influence on the flow direction of the fluid; (3) The greater the maximum depth of deformation, the greater the average flux.; (4) The larger the deformation width is, the average flux is larger in most cases, but the critical value of the driving frequency at which flow reversal occurs is also greater. Next, the influences of fluid viscosity and the size of pipe on the average flux are also analyzed. The results show that:The greater the fluid viscosity, the smaller the average flux generated by the deformation; The longer the pipe, and the smaller the diameter of the vessel, the smaller the average flux. In the second part, we add a pulsating flow at the entrance of the pipe. The variation of the average flux in the pipe under the two driving forces is analyzed, which are the pulsating flow and the deformation of tube wall, respectively. The results show that:When the driving frequency of pipe wall is equal to the pulsating frequency of pulsating flow or is a certain multiples, the average fluxes at outlet have a jump, that is, the resonance phenomenon of the fluid in pipe occurs.Under certain conditions, this model we proposed can effectively make the fluid in the tube form a directional flow, and pump a relatively higher net flow rate. Our study can help people understand the mechanism behind some complex phenomenon with complex boundary conditions, and also provides an idea and theoretical basis for the design of a new type and high-flux valveless micro-pump, which has certain theoretical significance and practical significance.