Analysis Of Boundary Slip Characteristics Based On Fluid/Solid Friction Interface

With the continuous advancement of micro/nano system technology,the effect of the slip effect between the fluid/solid interfaces on the micro/nano system has been gradually developed and studied in terms of frictional drag reduction,material preparation,biomedicine and fluid energy trap has great potential value.Due to the high complexity of the interface slip generation mechanism,which involves many factors and the limitation of scale effects,it has brought some difficulties to accurately measure the degree of slip by experimental means.According to the mechanism of the slip effect on the fluid energy capture,there is a close relationship between the interface wettability,the viscosity-slip motion of ions in the slip layer,and the fluid/solid friction,which provides new research for characterizing the degree of interface slip Ideas.This paper uses the three variables of material surface wettability,fluid flow rate and solution ion to bridge the flow/solid friction electric energy output and interface slip length,and carried out the following research.In the process of simulating the change of the slippage with the wettability of the interface,in order to quantitatively analyze the wettability of the solid surface,we first need to explore the regulation of the wettability of the material surface.In this paper,a droplet wetting model is constructed based on molecular dynamics methods.By calculating the change of the contact angle of the solid surface,the dependence of the surface wettability on the potential well parameters,the type of water molecules and the liquid scale in the simulation process is obtained Quantitative regulation of surface wettability.The results show that the potential well parameters between carbon and oxygen atoms are positively linearly related to the surface contact angle,and the contact angle of TIP3P water molecules is smaller than that of SPC/E and TIP4P water molecules;the radius of curvature of the liquid contact line It has a linear relationship with the cosine of its contact angle.By fitting the change curve and extending the extrapolation,the limit contact angles under different potential well parameters are obtained,thereby obtaining the wetting regulation law of continuous fluid.After that,a Coulter fluid model between parallel plates was built using a double-layer graphene structure to study the effect of solid surface wettability on the interface slip length;a carbon nanotube was used to build a Poiseuille fluid model in the tube,and other The influence of factors on the fluid-solid interface slip,such as the flow characteristics of microfluidics and the types of solute ions in microfluidics.The results show that the density and velocity distribution of the fluid will be affected by the strength of the solid/liquid interaction,and will be oscillated near the solid wall;under the same conditions,the stronger the hydrophobicity of the solid surface,the higher the degree of slippage.The contact angle satisfies L_s?c(1+?)^-2;for the study of fluid flow velocity,it is found that there is a critical flow velocity that abruptly changes the interface slip length;the dependence of solution ions on the interface slip length is affected by the size of the ion The effect of the number of charges.In terms of experiments,using hydrophobic materials as solid interface materials,fluid energy trapping chips based on microfluidic chips were processed through microelectrode fabrication,material film formation,and droplet chip preparation.In order to more accurately analyze the relationship between the output signal of the energy capture device and the boundary slip,a2D model of the fluid energy capture structure was established by the finite element simulation method,and the effects of various related factors on the output performance of the energy capture device were simulated..The results show that the output voltage between the electrodes has a negative correlation with the thickness of the dielectric layer,and the increase in the electrode spacing shows a change rule that increases first and then decreases,and changes with the ratio of the liquid length to the electrode width.Through fluid module,energy harvesting module and signal acquisition module,a fluid energy harvesting test platform based on microfluidic chip was built.By changing the contact angle of the surface of the energy harvesting chip,system flow rate and solution concentration,the interface wettability and fluid were studied respectively.The effect of speed and ion concentration on energy output.The results show that the weaker the wettability of the solid surface,the more conducive to the generation of triboelectric charge between the solid/liquid phase,and the greater the output electric energy,the overall relationship is linear;the speed of the liquid flowing through the energy-trapping structure is positive between the output of the electric energy There is a correlation,and when the flow rate of the aqueous solution increases to a certain extent,the output voltage exists in a saturated state;for the effect of solution ions,the results show that when the solution concentration is 0.01mol/L,the output voltage of the three ionic solutions is the highest.