Numerical Simulation Of Non-Newtonian Fluid Flow In Microchannels

The microfluidic system has the characteristics of less sample consumption,fast detection speed,multifunctional integration,etc.,and has great application potential in fields such as biochemistry.The detection samples involved in the microfluidic system are mostly non-Newtonian fluids.Therefore,exploring the flow characteristics of the non-Newtonian fluids in the microchannel is very important for the application of microfluidic systems.In this paper,based on the lattice Boltzmann method,the pressure drop and velocity difference of shear thinning fluid were simulated in bifurcated microchannels with various configurations,and the influence mechanism of fluid characteristics and microchannel geometry on non-Newtonian fluid flow behavior was analyzed.The main research contents include as follows.1.The non-Newtonian fluid power law model was introduced into the Newtonian fluid lattice Boltzmann model.The flow characteristics of the shear thinning fluid in a bifurcated microchannel with a rectangular cross section were numerically simulated.The effects of solution concentration,inlet velocity,and bifurcation angle on pressure drop were discussed.The results show that the pressure drop increases with increasing inlet velocity and solution concentration.The pressure drop of the microchannel with a bifurcation angle of 900 is the smallest.When the bifurcation angle is greater than 90°,the pressure drop decreases with the increase of the bifurcation angle.When the bifurcation angle is less than 90°,the pressure drop increases with the increase of the bifurcation angle.The pressure drop at each section of the microchannel is parabolic,and the maximum value appears at the middle section of the microchannel.Rheological properties are the most influential factors.2.The flow characteristics of shear-thinning fluid in bifurcation microchannels with constant flow rectangular cross sections were simulated,the effects of fluid rheological properties and microchannel geometry on the pressure drop and velocity difference of non-Newtonian fluids were analyzed.The results show that the pressure drop of the microchannel with a bifurcation angle of 90° is the smallest,and the pressure drop and speed difference increase with the increase of the inlet velocity,solution concentration,and bifurcation angle.The solution concentration makes the effect of inlet velocity and bifurcation angle on the pressure drop at the outlet more significant.Due to the rheological properties of the shear-thinning fluid,there is a stage in which the pressure value rapidly decreases during the flow.3.Based on the bifurcated microchannel,the two branch branches were constructed in an equal flow symmetrical configuration to simulate the flow of shear-thinning fluid in the microchannel,and the effects of solution concentration,inlet velocity and bifurcation angle on pressure drop and velocity difference were discussed.The results show that the maximum pressure and velocity in the microchannel appear near the bifurcation point.Pressure and velocity distributions are parabolic and symmetrical about the centerline of the microchannel.As the inlet velocity increases,the area of the pressure peak area at the bifurcation point increases significantly.The pressure drop and velocity difference increase with increasing inlet velocity and solution concentration.