非牛顿介质中图形化表面对减阻效果的影响

为研究图形化表面在非牛顿介质中对减阻效果的影响,在微摩擦试验机(UMT)上进行了销盘润滑实验。实验中在硅片的表面刻蚀了纵向和横向2种沟槽以形成不同的表面图形。实验表明,与光滑表面相比,当剪切速率处于牛顿流动区时,沟槽具有一定的减阻效果;而当剪切速率处于剪切稀化区时,沟槽表面的阻力上升;并且横向沟槽表面的阻力总是大于纵向沟槽表面的阻力。流体数值计算的结果表明,横向沟槽侧壁的压差阻力和纵向沟槽侧壁的粘性阻力无法完全补偿沟槽底面上的阻力损失,因而产生了减阻效果。

Effect of Surface Patterns on Drag Reduction in Non-Newtonian Fluid

To investigate the surface patterns effect on drag force in non-Newtonian fluid lubrication,longitudinal and transverse surface patterns were etched and a pin-disk lubrication experiment was performed on the disk in Universal Micro Tribometer system.Compared with smooth surface,the drag reduction effect occurs on surface patterns in Newtonian field of the fluid,while the drag increment occurs in shear thinning field of the fluid.The drag force on surface with transverse grooves is higher than that on surface with longitudinal grooves.Numerical results based on CFD method give the explanations.The pressure drags generated on side walls of the transverse grooves and the viscous drag on side walls of the longitudinal grooves can not totally compensate the loss of drags on the bottom walls of the grooves,then the drag reduction occurs on rough surface.However,the difference of drag loss on pattern walls and on smooth surface is weakened by the shear thinning fluid,and the drag reduction effect caused by the surface pattern effect may not appear in the shear thinning field.