Microscale Flow Resistance Characteristics

Flow characteristics are considered to be significant ingredients in manufacture of micro devices and the design of micro machine accessories, thereby the researches on this issue have important instruction meanings theoretically.Plenty of researches on micro flow have been conducted all over the world, and phenomena different from macro ones have been detected. some neglectable factors in macro flow are contributed to important effects, such as scale effect,surface effect and slippage condition etc. Several models were brought forward, trying to explain the differences, but consistently acknowledged conclusion was not reached.This paper focuses on the friction characteristics and its function mechanism in micro channels through experiments and numerical value calculation, divided into several aspects as follows:(1) Expanded the condition of fully developed laminar flow through rough tubes, introduced the conception of velocity profile presents periodic distribution along the axial direction. Based on this hypothesis, testified that the product of Darcy friction factor and Renault number (Re) was independent of Re. This assumption was validated via finite element method. Consequently, this paper pointed out the ascription to Re effect for friction factor's increase is not appropriate.(2) As far as the influence mechanism of surface roughness to micro flow, this paper indicated that slight disturbances maybe existed in micro channels during former researches, which may well enhanced the effect of surface roughness. Based on this assumption, we designed steady pressure root drived by high-pressure Nitrogen, and assembled fitting (water power diameter 600μm approximately) to measure flow resistance. As to the problems in experiments, put forward improvement scheme to satisfy experimental requirements.(3) 5# principal axis lubricating oil and 1-Propanol were chose as work media, whose flow phenomena through three tubes with various roughness was studied. This paper deal with experimental data properly, analyzed the potential errors, finally possible mechanism explanations were given.(4) Porous Medium Layer(PML) experiment simulation of surface roughness. Particles were filled in tube to make tube's one face became porous layer, in order to create high surface roughness environment.