基于格子Boltzmann方法的分叉微通道内非牛顿流体流动特性研究

Flow Characteristics of Non-Newtonian Fluid in Bifurcation Microchannel Based on Lattice Boltzmann Method

为探究分叉微通道内非牛顿流体的流动特性,将非牛顿流体幂律模型引入牛顿流体格子Boltzmann模型,在不同分叉角度矩形截面微通道内数值模拟不同质量分数剪切稀化流体的流动行为;通过分析流动过程中密度随时间的变化趋势以及稳态流动下的密度,得到微通道内压力的分布以及流动区间的压力降;分析溶液质量分数、入口速度与分叉角度对非牛顿流体流动特性的影响,探讨流体特性和微通道几何构型对非牛顿流体流动行为的影响机制。结果表明:分叉角度为90°的微通道内流体的压力降最小,当分叉角度大于90°时,压力降随着分叉角度的增大而减小,当分叉角度小于90°时,压力降随着分叉角度的增大而增大;流体入口速度和流体溶液质量分数增大,压力降均增大;流体溶液质量分数增大使得分叉角度和入口速度对出口处压力降的影响更为显著;微通道内各截面处压力降分布呈抛物线形。

In order to explore flow characteristics of non-Newtonian fluid in bifurcation microchannel,the non-Newtonian fluid power law model was introduced into Newtonian fluid lattice Boltzmann model,and the flow behaviors of shear thinning fluid with different mass fraction were numerically simulated in rectangular cross-section microchannels with different bifurcation angles.The pressure distribution in the microchannel and the pressure drop in the flow region were obtained by analyzing the change trend of density with time in the flow process and the density under steady flow.The effects of solution mass fraction,inlet velocity and bifurcation angle on the flow characteristics of non-Newtonian fluid were analyzed,and the influence mechanism of fluid characteristics and micro channel geometry on the flow behavior of non-Newtonian fluid was discussed.The results show that the pressure drop of fluid in microchannel with 90°bifurcation angle is the smallest.The pressure drop is decreased with the increasing of bifurcation angle when the bifurcation angle is greater than 90°.However,the pressure drop is increased with the increasing of bifurcation angle when the bifurcation angle is less than 90°.The higher solution concentration makes the influence of the bifurcation angle and the inlet velocity on the pressure drop at the outlet more significant.The pressure drop at each section in the microchannel is parabolic.