A Study On The Macromolecular Suspension Flow In Micro-Channel Using Energy-Conserving Dissipative Particle Dynamics Simulation

In recent years,as the rapid development of micro-fabrication technology,the micro-fluidic chips,biological micro-devices,micro-medical robots and other micro-devices have been design and manufacture in the biological and medical engineering.For example,benefited from interpreting macroscopic features through understanding their corresponding microscopic nature by using micro-fluidic chips technology,it becomes possible to achieve accurate diagnosis and effective treatment of diseases in a wide range of life sciences and pharmaceutics applications.However,analyzing and understanding the flow characteristics of macromolecular suspensions are required for the design and manufacture of such microfluidic chips.At present,a lot of research has been explored and analyzed the flow characteristics of macromolecular suspensions under isothermal systems.In real physical environment,heat exchange and transmission are widely presented in microfluidic chip,and play an important role on the dynamic behaviors of suspension and macromolecule aggregates.Therefore,exploring the complex dynamics of heat and macromolecules coupling in this work will in turn become beneficial for promoting biological and medical advancement.In this paper,the numerical method of energy conservation dissipative particle dynamics is selected,and then the dynamic behaviors of macromolecule under complex thermal conditions are investigated in micro-channel.For the microchannel structure,the periodic boundary conditions are applied in the direction of fluid flow,and a non-slip boundary and Maxwell's reflection fusion are proposed in the two solid walls of the microchannel.For the macromolecular model,combining with the macromolecular chain properties detected by microfluidic chips,the worm chain model is select.The specific research contents and important conclusions are as follows:(1)The modify power law function suitable for non-isothermal systems is proposed.At present,the fluid flow properties of macromolecular suspensions do not take into account temperature changes.Base on the Navier-Stokes equation,the classical power law function under the isothermal system is derived,which the power law index n=1 is Newton fluid and n?1 is a power law fluid.And then the relationship between temperature and fluid viscosity is introduced to obtain the modified power law function.The effectiveness of modify power law function was verified using the velocity distribution of the suspension under temperature gradient.The results show that the macromolecular suspension is conforming to power-law fluid flow properties that have the phenomenon of "shear thinning".As the system temperature decreases,the power law index n decreases,and the fluid is non-Newtonian.(2)The velocity and stress fields of macromolecular solutions with different thermal convection conditions and concentrations,as well as their coupling effects are comparatively analyzed.It is concluded that the influence of macromolecular chain concentration on the velocity of motion and the normal stress field is more obvious than that of temperature,which the effect of temperature is weakened as the concentration increases.(3)The velocity and stress filed distribution of macromolecular suspension considering various chain lengths under different thermal gradients are investigated.The coupled length-thermal effect is also studied in detail.The results show that the thermal gradients has little effect on the stress field distribution,and the concentration has little effect on the shear stress distribution and has obvious influence on the normal stress distribution.At low concentration,the thermal gradient has obviously effect on the velocity,and then the effect of temperature change on the velocity becomes less significant as the concentration increases.(4)The temperature distribution of the suspension is investigated systemically in the micro-channel under three different temperature conditions,such as thermal convection,constant temperature wall and temperature gradient.And then the temperature distribution cloud and temperature profile were obtained in the channel under different conditions.In addition,the velocity of suspension and the migration and behaviors of macromolecules are comparatively analyzed.The results show that the thermal convection conditions for is consistent the velocity profile with the constant temperature wall conditions.For the all case,in the extended area on the right side of micro-channels,the phenomenon of reflow has occurred and the velocity value is greater than the velocity value in the left extension area.(5)In addition,the distribution,migration and behaviors of macromolecules are investigated systemically as well as the flow of macromolecular solutions in micro-channel under three different temperature conditions.The results show that the temperature effect on the macromolecular suspension flow is significant,and has a significant effect on the distribution,migration and motion behavior of macromolecules.The high temperature promotes the stretching of macromolecules.