Transport Property Of Rough Microchannel And Its Application In Porous Media

Microfluidic technology is widely used in the fields of micro-electromechanical systems and photoelectric materials,and the transport properties of rough microchannel are important for the development of microfluidic technology.Furthermore,the transport characteristics of rough microchannel are significant for the physical properties of porous media.Therefore,the study on the transport properties and physical mechanisms of rough microchannel is of great scientific and practical significance for the fields of optoelectronic materials,porous materials,micro-electromechanical systems and microfluidic technology.There are many factors affecting the transport properties of rough microchannels,and their interaction mechanisms are very complex.Thereinto,the surface effect induced by rough surface plays a dominant role in the transport process of rough microchannel.It has been proven that rough surface indicates a fractal scaling law in a certain scale range.Therefore,the rough surface is characterized by fractal geometry theory in the present work.The transport properties and mechanisms of rough microchannel are studied by theoretical analysis and numerical simulation,and the applications of rough microchannel in micro-nano porous media are also discussed.The main contents and results are listed as follows:(1)Flow characteristics in rough microchannel: the geometrical structures of rough microchannels are constructed by using regular rough element model and fractal rough element model respectively.The effects of inlet velocity,surface roughness,rough element shape and fractal dimension of rough surface on flow characteristics in rough microchannel are investigated.The relationships between Poiseuille number and surface roughness,Reynolds number and fractal dimension are also proposed.The numerical results show that the present mathematical model is in good agreement with experimental data.And the geometry of rough element and roughness indicate significant effect on the flow properties in rough microchannel.The flow resistance and Poiseuille number increase with the increase of the fractal dimension under the same surface roughness,which can be explained as that the larger fractal dimension,the more irregular the rough surface.(2)Rough microchannels in porous media: a fractal capillary bundle model of porous media is established,where the rough surface of microchannels are taken into account.The effective permeability of porous media is deduced accordingly,and seepage flow in a fractal rough microchannel is also simulated.The results show that the increase of fractal dimension for pore size distribution induces the increase of porosity and permeability of porous media.And the flow resistance increase and the permeability of micro-nano porous media decreases with the increase of fractal dimension for rough surface.(3)Rough microchannel in fractured porous media: a fractal dual-media model is developed for the fractured porous media.Considering the rough surfaces of micro-cracks,a scaling relationship between the permeability and fraction of cracks of fractured porous media is obtained.The results show that the increase of fractal dimension for fracture aperture and the decrease of fractal dimension for fracture length can enhance the permeability of fractured porous media.Rough surface may take an important influence on the transport process of micro-cracks,and the permeability decreases with increased surface roughness.This study has important scientific significance for understanding the transport mechanism of rough microchannels and seepage flow in porous media,and may be helpful for the development of optoelectronic materials,porous materials,micro-electromechanical systems,micro-fluidic technology,microchannel cooling,fuel cells and unconventional oil and gas resources etc.