Molecular Dynamics Simulation Study Of The Rheological Properties Of Water-based Silver Nanofluids

Nanofluids have wide application potential in many important fields such as efficient heat transfer and cooling.Therefore,the thermophysical properties of these fluids have become an important research topic in recent years.Viscosity is a very important property of nanofluids.Especially in the practical applications of fluid flow and heat transfer,convective heat transfer and pumping power are directly related to the viscosity coefficient.However,the research on the viscosity of nanofluids is not indepth enough.Traditional experimental methods can only observe phenomena from the perspective of phenomenology,and the conclusions obtained from different studies are quite inconsistent,and it is difficult to explain the microscopic mechanism.Therefore,this paper uses molecular dynamics methods based on accurate potential energy models to simulate real materials to study the interaction of nanofluids,so as to understand the enhancement mechanism of the viscosity coefficient of nanofluids,which is of great significance in the engineering field involving precise fluid control.This dissertation introduces the current research status of molecular dynamics of nanofluid viscosity,and points out the limitations of traditional empirical models and experimental methods.Empirical models cannot predict the viscosity of nano-scale particle suspensions,and the experimental methods are difficult to reach a unified conclusion.Then compare The three rigid water models SPCE,TIP3 P,TIP4P\2005 are used to predict the accuracy of viscosity.The TIP4P/2005 water model and Lennard-Jones potential function are used to establish the base fluid system,and the shear viscosity of the base fluid at different temperatures is calculated.The comparison with the experimental value verifies the accuracy of the water model in predicting viscosity.A nanofluid model was established between metallic silver particles and TIP4P\2005 water-based liquid system,and the Morse force field was used to describe the interaction between silver atoms.The volume fraction of silver particles,environmental temperature,and particle size were used as variables to investigate the effects of three factors The influence of viscosity is calculated by using the equilibrium molecular dynamics viscosity calculation method based on the Green-Kubo formula to calculate the fluid shear viscosity under different conditions.Then,the reverse non-equilibrium molecular dynamics method(MullerPlathe)was used to verify the accuracy of the equilibrium calculation results.At the same time,the self-diffusion coefficient and the relationship between the shear viscosity and the shear rate of the nanofluid under different volume fractions were calculated.The rheological properties of the fluid.The calculation results of the viscosity correlation of water-based silver nanofluid show that volume fraction,temperature and particle size all affect the shear viscosity value.The viscosity value is negatively correlated with temperature,the volume fraction and viscosity value are positively correlated,and the particle size has an effect on viscosity.The influence of slab is small,the particles decrease,and the viscosity value increases slightly.Nanofluids with high volume fractions exhibit non-Newtonian rheological properties of shear thinning.Through the analysis of the radial distribution function of the fluid system,the addition of silver particles significantly affects the fluid structure.The strong interaction of the particles with water molecules at high volume fractions has a greater impact on the atomic distribution,resulting in the formation of particles and water molecules.Microstructure,which is the main reason for the increase in viscosity and shear thinning of nanofluids.