Study On The Flow Resistance And Interference Of Porous Media

As the name implies,a porous medium is an object with pores inside.The pores inside are random and supported by a solid skeleton.Porous media are closely related to our lives and can be seen everywhere,such as soil,sand,wood,etc.,or bread,sponges,clothes,ceramics,etc.in life.Even as large as the universe is as small as atoms,it belongs to the category of porous media from a certain perspective.In various industrial,agricultural and other production activities in today's society,the mass,momentum,and energy transmission phenomena of porous media generally exist.It is of great significance to study the flow resistance of porous media,but its flow is very complicated.Mainly due to the random solid structures everywhere in the fluid path.This structure completely changes the flow field: it destroys the boundary layer and forces the fluid only through curved open flow channels.These effects cause violent mixing and the appearance of an additional mechanism called dispersion.Therefore,the pressure drop in the porous medium is much higher compared to the open area flow.This brings a lot of trouble to the research inside the porous media.This article first introduces the flow resistance model in Wu Jinsui's doctoral thesis and analyzes its problems.Secondly,it gives reasonable results and the above model formulas and comparisons with experiments.Once again,the fractal flow and traditional flow and experiments are compared and analyzed.Modified ideas: First,the integral of the flow around a single sphere is the sum of the resistances of all layers of all the spheres;second,the upper limit of the integral ? is calculated by the particles(available bed volume= N single average particle volume);or the average particle size To determine the multiple,the multiple can be determined using experimental data);Third,for the three-dimensional particle packing model,it is not reasonable to use one-dimensional calculation for the total resistance single-layer height,so the unit volume can be used.It is concluded that the fractal flow around the particles can not solve the nonlinear problem of porous media flowonly from the structure.Finally,a tube flow plus bypass flow model and a reasonable particle fractal theory are proposed.The flow resistance of the porous medium is reduced to the viscous and inertial terms.The total resistance formula is derived from the traditional and fractal aspects.Among them,the inertial term is expressed by the resistance to flow around,and multiple sets of experimental data are used to determine the range of the constant C before the flow.In this paper,the relevant quasi-numbers are derived through the dimension analysis method,the expression form of the obtained resistance and the influencing factors of the Ergun equation coefficients are studied.The Ergun equation coefficient is a function of the average particle diameter,specific surface area,tortuosity,and relative roughness,and ultimately needs to be determined through experiments or other methods.Finally,the relationship between the interference coefficient and the porosity of the Yang Zhonggeng partition model is analyzed.The ratio of the traditional formula(Carmen's equation or Egen's equation)and the traditional flow is used to obtain the interference coefficient of the traditional flow.Eight sets of different porosity and its The corresponding correction coefficients were fitted with matlab to obtain the relationship between the porosity and the interference coefficient,and eleven sets of different porosities and corresponding interference coefficients were used to verify the simplified form of the fitted formula.In the first four areas,4-6 sets of experimental data were used for verification and correction.The results show that the relationship between porosity and interference coefficient is reasonable.