Research On Wettability Of Droplets On Microstruc-Ture Surface Based On Boltzmann Method

In recent years,the wettability of microstructures has been paid more and more attention.Surface microstructure can enhance the wettability of surface and form superhydrophobic and super-hydrophilic surface.Therefore,it is widely used in life,medicine,microorganism research and MEMS,etc.However,the fluid-solid interaction of microstructural surfaces is very complex,which requires very strict requirements on the precision of surface preparation and the wetting observation methods between microstructures.Therefore,it is often difficult to accurately observe the wetting effect of the surface under experimental conditions.Therefore,the study of the wetting behavior of fluid by means of numerical calculation has important theoretical guiding significance.Lattice-Boltzmann method is a fluid numerical simulation method for mesoscopic fluid flow and collision process by means of discrete fluid distribution function.It has the advantages of both macroscopic fluid mechanics and microscopic molecular mechanics,as well as the advantages of easy implementation of boundary conditions,good parallelism and simple programming.It has been widely used in fluid motion and engineering problems.In this paper,the infiltration process of droplet on the surface of microstructures is studied by using pseudo potential lattice Boltzmann method.The main research contents are as follows:1.The pseudo-potential lattice Boltzmann method was used to construct the single-component multiphase flow LBGK model and the droplet model.The thermodynamic P-R state equation was introduced into the potential function to expand the density ratio of the two-phase fluid to meet the practical requirements.The influence of different fluid-solid forces on the fluid with high density ratio is analyzed,and a new fluid-solid force is adopted to prevent the initial oscillation velocity from being too large.2.Verification of the model done,through the flow of different ? flow interaction force and the theoretical solution of the thermodynamic state equation under the structure of Maxwell,simulation curves are determined when the ?=1.238 part in the gas phase and the theoretical solution error is only 2%or so,more consistent with the theoretical value,the model satisfy the conservation of mass,after enough time of relaxation process,The surface tension of the model is consistent with that at normal temperature(23°),and the false velocity is well controlled.The calculated contact Angle of droplets on the smooth wall surface is in good agreement with the experimental comparison.3.The boundary shape of the bottom was reconstructed to control the intrinsic contact Angle of the solid surface,and the droplet movement and contact Angle change of PDMS,passivated and non-passivated silicon surfaces were simulated under different microstructure spacing;The contact angles of droplets with different microstructures measured on the corresponding surfaces were compared with the simulation results.It was found that the difference of the contact angles between the simulation and the experiment was less than 5°,and the simulation results were in good agreement with the experimental measurements.The influence of microstructure parameters on the surface wettability of the droplet and the wetting process of the liquid in the microstructure were analyzed.