Research On Contact Angle Measurement Algorithm Based On Lattice Boltzmann Method

Multiphase flow is not only ubiquitous in life,but also widely used in many natural phenomena and industrial production.A better understanding and study of the mechanism and performance of multiphase flow can not only help people understand nature and create more value in industrial production,but also have important significance in scientific progress and energy extraction.Surface wettability,as an important property in multiphase flow,is used to characterize the ductility of liquids on solid surfaces and is measured by the size of the contact angle.The contact angle is the characteristic angle formed by the contact position between the liquid surface and the solid surface.It is the basic characteristic quantity of many industrial applications and natural phenomena.It has important applications in self-cleaning,new materials,energy development,etc.,so research the contact angle has important practical significance.Although the existing contact angle measurement methods can obtain the final required results,most of them require sophisticated instruments,tedious processes and complex calculations.Therefore,a simple and efficient algorithm for calculating the contact angle is needed.In recent years,the lattice Boltzmann method has become a very effective tool for studying multiphase flow because of its natural parallelism and high efficiency,and it is widely used in a variety of complex fluid systems.Therefore,this paper uses the lattice Boltzmann method combined with the high density ratio chemical potential model to study the contact angle measurement algorithm.The main work content is as follows:1?For the original algorithm of using the chemical potential multiphase flow model to calculate the contact angle of the liquid drop on the plate,the measurement error increases when the measurement error is increased in the hydrophobic state,the algorithm is improved.Use higher-precision quadratic interpolation instead of linear interpolation to determine accurate gasliquid interface points and three-phase contact points.Through the verification of the algorithm,it is found that the contact angle of the liquid droplet on the flat plate measured by the improved algorithm is closer to the theoretical value in the hydrophobic state,and the result is more accurate.Further,the improved algorithm is applied to the super high density ratio model.It is verified by simulation that the improved algorithm can also calculate the contact angle of the droplet on the flat plate in the super-high density ratio model.The result obtained by the improved algorithm is in good agreement with the theoretical value.At the same time,the improved algorithm applied in the super-high density ratio model can calculate the contact angle of droplets at lower temperatures.2?Furthermore,an algorithm for measuring the contact angle of droplets on the curved surface is proposed.The Boltzmann method of large density ratio lattice based on chemical potential was used for modeling,and the droplets on convex and concave surfaces were simulated.The contact angle between the drop and the curved solid surface was measured without considering the gravity.The change of contact angle under different wetting conditions has been compared with theoretical values to verify the correctness of the algorithm.In addition,it is simulated whether the quality of the droplet and the radius of curvature of the curved surface will affect the contact angle of the droplet.The results show that when the chemical potential is constant,the contact angle obtained by the proposed algorithm for the same droplet under different curvatures of the curved surface will not change;when the chemical potential is constant,different droplets are used under the same curvature of the curved surface.The contact angle obtained by the proposed algorithm will not change,which is consistent with the verified theoretical expectations.It is proved that the proposed algorithm is grid-independent.This algorithm is used to measure the contact angle of the droplet under gravity.The results show that the simulation results of this algorithm remain unchanged under the same chemical potential,which is consistent with the theoretical expectation that the microscopic contact angle has nothing to do with gravity.In summary,the algorithm for measuring contact angle proposed in this paper is accurate,simple and efficient.It is not only suitable for the Boltzmann method of chemical potential lattice with high density ratio,but also can be extended to other multiphase flow models in the simulation of contact angle correlation.