Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main facto...Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main factors, which affect the development of the theory on oil and gas porous flow. The development law and development route of the mechanics of fluids in porous media are also summarized in this paper.展开更多
This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a ...This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.展开更多
The purpose of this work is to predict the state of collapse in shallow tunnel in layered strata by using a new curved failure mechanism within the framework of upper bound theorem.Particular emphasis is first given t...The purpose of this work is to predict the state of collapse in shallow tunnel in layered strata by using a new curved failure mechanism within the framework of upper bound theorem.Particular emphasis is first given to consider the effects of seepage forces and surface settlement.Furthermore,the Hoek-Brown nonlinear failure criterion is adopted to analyze the influence of different factors on the collapsing shape.Two different curve functions which describe two different rock layers are obtained by virtual work equations under the variational principle.According to the numerical results,the parameter B in Hoek-Brown failure criterion and the unit weights in different rock layers have a positive relationship with the size of collapsing block while pore pressure coefficient and the parameter A in Hoek-Brown failure criterion present a reverse tend.展开更多
Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical part...Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical particles. The standard k-ε turbulence model and a methane oxidation mechanism with 23 species and 39 elemental reactions were used. Various equivalence ratios （1.47, 1.88, 2.12 and 2.35） were studied. The numerical results showed good agreement with the experimental data. For ultra-rich mixtures, the combustion temperature exceeds the adiabatic value by hundreds of centigrade degrees. Syngas （hydrogen and carbon monoxide） can be obtained up to a mole fraction of 23%. The numerical results also showed that the combination of CFD with detailed chemical kinetics gives good performance for modeling the pseudo-homogeneous flames of methane in porous media.展开更多
Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different g...Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different gas adsorption contents were performed,and the influence law of adsorption on coal permeability was studied.At the sametime,experimental analogy showed clearly that gas drawing plucks the permeability variationlaw.The results show that adsorption has a major impact on coal permeability.Thegreater the adsorption,the more the gas adsorption capacity and the coal permeabilitybecomes smaller.Permeability becomes smaller along with confining of pressure andtemperature,and this is in accord with local practice results.展开更多
Based on the steady-state seepage method, we used the Mechanical Testing and Simulation 815.02 System and a self-designed seepage instrument for over-broken stone to measure seepage properties of water flows in three ...Based on the steady-state seepage method, we used the Mechanical Testing and Simulation 815.02 System and a self-designed seepage instrument for over-broken stone to measure seepage properties of water flows in three types of crushed rock samples. Three methods of confidence interval in describing permeability coefficients are presented: the secure interval, the calculated interval and the systemic interval. The lower bound of the secure interval can be applied to water-inrush and the upper bound can solve the problem of connectivity. For the calculated interval, as the axial pressure increases, the length of confidence interval is shortened and the upper and lower bounds are reduced. For the systemic interval, the length of its confidence interval, as well as the upper and lower bounds, clearly vary under low axial pressure but are fairly similar under high axial pressure. These three methods provide useful information and references for analyzing the permeability coefficient of over-broken rock.展开更多
In order to reveal the law of raw coal seepage at different gas pressures, the gravity constant load seepage experimental system was developed and used. The law of raw coal seepage at different gas pressures with He, ...In order to reveal the law of raw coal seepage at different gas pressures, the gravity constant load seepage experimental system was developed and used. The law of raw coal seepage at different gas pressures with He, N2 and CO2 was investigated. The results show that, in a given state of stress during the experiment, with the increase of gas pressure, the permeability of raw coal sample prone to outburst exhibits a significantly decrease, and then exhibits an increasing trend when reaching the extreme point. The law of Klingberg coefficient related to the stress state and the gas adsorption properties was also obtained. Under the same experimental conditions, the Klingberg coefficient of He is greater than that of N2; and the Klingberg coefficient of CO2 has minimum value; so the stronger the gas adsorption is, the smaller the Klingberg coefficient of gas goes. Klinkenberg coefficient decreases with the increase of effective stress. Under the same conditions, the permeability of He is greater than that of N2; the permeability of CO2 has minimum value; so the stronger the gas adsorption is, the lower the permeability of the coal sample goes. The results have important significance in revealing the mechanism of gas seenage. Dredicting coal mine gas disaster, and gas drainage and safety nroduction.展开更多
The present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity sys...The present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity system is investigated with computational fluid dynamics. A total variation diminishing scheme is employed to solve the unsteady, two-dimensional, compressible, Navier-Stokes equations. The Mach number of an initial shock wave is changed in the range from 1.02 to 1.12. Several different types of porous wall/cavity systems are tested to investigate the passive control effects. The results show that wall pressure strongly fluctuates due to diffraction and reflection processes of the shock waves behind the incident shock wave. From the results, it is understood that for effective alleviation of tunnel impulse waves, the length of the perforated region should be sufficiently long.展开更多
In this paper, we have discussed the food movement in stomach with thermal bound- ary conditions. Eyring-Prandtl fluid model is considered. Formulation of the considered phenomena have been developed for both fixed an...In this paper, we have discussed the food movement in stomach with thermal bound- ary conditions. Eyring-Prandtl fluid model is considered. Formulation of the considered phenomena have been developed for both fixed and moving frame of references. Regular perturbation is used to find the solution of stream function, temperature profile and pressure gradient. Analysis has been carried out for velocity, ＂stream function, temper- ature, pressure gradient and heat transfer＂. Appearance of pressure gradient is quite complicated so to get the expression for pressure rise we have used numerical integra- tion. It is perceived that the velocity close to the channel walls is not same in outlook of the Eyrin^Prandtl fluid parameter taken as fl and Hartman number M. The velocity decreases by increasing β and M.展开更多
After analyzing many studies of fluid flow theory of multi-porous media in low and extra-low permeability reservoirs and the numerical simulation of non-Darcy flow, we found that a negative flow rate occurs in the exi...After analyzing many studies of fluid flow theory of multi-porous media in low and extra-low permeability reservoirs and the numerical simulation of non-Darcy flow, we found that a negative flow rate occurs in the existing non-Darcy flow equation, which is unreasonable. We believe that the existing equation can only be considered as a discriminant to judging Darcy flow or non-Darcy flow, and cannot be taken as a fluid flow governing equation of multi-porous media. Our analysis of the experimental results shows that the threshold pressure gradient(TPG) of low and extra-low permeability reservoirs is excessively high, and does not conform to fluid flow through multi-porous media in the actual reservoir situation. Therefore, we present a reasonable TPG ranging from 0.006 to 0.04 MPa/m at the well depth of 1500 m and oil drainage distance of 500 m. The results of our study also indicate that the non-Darcy flow phenomenon will disappear when the TPG reaches a certain value. In addition, the TPG or non-Darcy flow in low and extra-low permeability reservoirs does not need to be considered in the productivity prediction and reservoir numerical simulation. At present, the black oil model or dual-porous media is suitable for simulating low and extra-low permeability reservoirs.展开更多
For nonlinear coupled system of multilayer dynamics of fluids in porous media, the second order and first order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward, trod...For nonlinear coupled system of multilayer dynamics of fluids in porous media, the second order and first order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward, trod two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques, such as calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates, are adopted. Optimal order estimates in L2 norm are derived to determine the error in the second order approximate solution. This method has already been applied to the numerical simulation of migration-accumulation of oil resources.展开更多
A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The ...A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The flow is characterized by three parameters： /3 the ratio of radius to length of the arterial segment, Re the characteristic Reynolds number associated with the pressure outside the arterial segment and c the filtration coe^cient. The problem has been solved by the use of a perturbation technique, e is considered to be very small, ensuring the validity of the perturbation method. The computed numerical results are presented graphically to depict the variations in velocity, volumetric flow rate, wall shear stress and flow resistance.展开更多
文摘Through reviewing the flow theory’s birth and development history in underground porous media and contrasting the mechanics of underground fluids and mechanics of viscous fluids, this paper points out the main factors, which affect the development of the theory on oil and gas porous flow. The development law and development route of the mechanics of fluids in porous media are also summarized in this paper.
文摘This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.
基金Project(51378510) supported by the National Natural Science Foundation of ChinaProject(2017zzts157) supported by the Innovation Foundation for Postgraduate of Central South University,China
文摘The purpose of this work is to predict the state of collapse in shallow tunnel in layered strata by using a new curved failure mechanism within the framework of upper bound theorem.Particular emphasis is first given to consider the effects of seepage forces and surface settlement.Furthermore,the Hoek-Brown nonlinear failure criterion is adopted to analyze the influence of different factors on the collapsing shape.Two different curve functions which describe two different rock layers are obtained by virtual work equations under the variational principle.According to the numerical results,the parameter B in Hoek-Brown failure criterion and the unit weights in different rock layers have a positive relationship with the size of collapsing block while pore pressure coefficient and the parameter A in Hoek-Brown failure criterion present a reverse tend.
基金Supported by the National Natural Science Foundation of China （20307007, 50576081） and the Natural Science Foundation of Zhejiang Province （R 107532）, Program for New Century Excellent Talents in University （NCET-07-0761） and a Foundation for the Author of National Excellent Doctoral Dissertation of China （200747）.
文摘Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical particles. The standard k-ε turbulence model and a methane oxidation mechanism with 23 species and 39 elemental reactions were used. Various equivalence ratios （1.47, 1.88, 2.12 and 2.35） were studied. The numerical results showed good agreement with the experimental data. For ultra-rich mixtures, the combustion temperature exceeds the adiabatic value by hundreds of centigrade degrees. Syngas （hydrogen and carbon monoxide） can be obtained up to a mole fraction of 23%. The numerical results also showed that the combination of CFD with detailed chemical kinetics gives good performance for modeling the pseudo-homogeneous flames of methane in porous media.
文摘Using self-developed gas-seepage experimental installation,under the sameeffective stress conditions,coal permeability experiments on different adsorption characteristicsof gases,different temperatures and different gas adsorption contents were performed,and the influence law of adsorption on coal permeability was studied.At the sametime,experimental analogy showed clearly that gas drawing plucks the permeability variationlaw.The results show that adsorption has a major impact on coal permeability.Thegreater the adsorption,the more the gas adsorption capacity and the coal permeabilitybecomes smaller.Permeability becomes smaller along with confining of pressure andtemperature,and this is in accord with local practice results.
基金Financial support for this work, provided by the National Natural Science Foundation of China (Nos. 50774083 and 41074040)the Program for New Century Excellent Talents in University (No. NCET-07-0803)the National Key Basic Research Program (No. 2009CB219605)
文摘Based on the steady-state seepage method, we used the Mechanical Testing and Simulation 815.02 System and a self-designed seepage instrument for over-broken stone to measure seepage properties of water flows in three types of crushed rock samples. Three methods of confidence interval in describing permeability coefficients are presented: the secure interval, the calculated interval and the systemic interval. The lower bound of the secure interval can be applied to water-inrush and the upper bound can solve the problem of connectivity. For the calculated interval, as the axial pressure increases, the length of confidence interval is shortened and the upper and lower bounds are reduced. For the systemic interval, the length of its confidence interval, as well as the upper and lower bounds, clearly vary under low axial pressure but are fairly similar under high axial pressure. These three methods provide useful information and references for analyzing the permeability coefficient of over-broken rock.
基金supported by the Fundamental Research Funds for the Central Universities (No. 2011QZ02)the National Natural Science Foundation of China (No. 51204189)the National Basic Research Program of China (No. 2011CB201202)
文摘In order to reveal the law of raw coal seepage at different gas pressures, the gravity constant load seepage experimental system was developed and used. The law of raw coal seepage at different gas pressures with He, N2 and CO2 was investigated. The results show that, in a given state of stress during the experiment, with the increase of gas pressure, the permeability of raw coal sample prone to outburst exhibits a significantly decrease, and then exhibits an increasing trend when reaching the extreme point. The law of Klingberg coefficient related to the stress state and the gas adsorption properties was also obtained. Under the same experimental conditions, the Klingberg coefficient of He is greater than that of N2; and the Klingberg coefficient of CO2 has minimum value; so the stronger the gas adsorption is, the smaller the Klingberg coefficient of gas goes. Klinkenberg coefficient decreases with the increase of effective stress. Under the same conditions, the permeability of He is greater than that of N2; the permeability of CO2 has minimum value; so the stronger the gas adsorption is, the lower the permeability of the coal sample goes. The results have important significance in revealing the mechanism of gas seenage. Dredicting coal mine gas disaster, and gas drainage and safety nroduction.
文摘The present computational study addresses the attenuation of the shock wave propagating in a duct, using a porous wall/cavity system. In the present study, a weak shock wave propagating over the porous wall/cavity system is investigated with computational fluid dynamics. A total variation diminishing scheme is employed to solve the unsteady, two-dimensional, compressible, Navier-Stokes equations. The Mach number of an initial shock wave is changed in the range from 1.02 to 1.12. Several different types of porous wall/cavity systems are tested to investigate the passive control effects. The results show that wall pressure strongly fluctuates due to diffraction and reflection processes of the shock waves behind the incident shock wave. From the results, it is understood that for effective alleviation of tunnel impulse waves, the length of the perforated region should be sufficiently long.
文摘In this paper, we have discussed the food movement in stomach with thermal bound- ary conditions. Eyring-Prandtl fluid model is considered. Formulation of the considered phenomena have been developed for both fixed and moving frame of references. Regular perturbation is used to find the solution of stream function, temperature profile and pressure gradient. Analysis has been carried out for velocity, ＂stream function, temper- ature, pressure gradient and heat transfer＂. Appearance of pressure gradient is quite complicated so to get the expression for pressure rise we have used numerical integra- tion. It is perceived that the velocity close to the channel walls is not same in outlook of the Eyrin^Prandtl fluid parameter taken as fl and Hartman number M. The velocity decreases by increasing β and M.
基金sponsored by National Key Project of Science and Technology of the Ministry of Science and Technology(MOST)(Grant No.2011ZX05043-002)
文摘After analyzing many studies of fluid flow theory of multi-porous media in low and extra-low permeability reservoirs and the numerical simulation of non-Darcy flow, we found that a negative flow rate occurs in the existing non-Darcy flow equation, which is unreasonable. We believe that the existing equation can only be considered as a discriminant to judging Darcy flow or non-Darcy flow, and cannot be taken as a fluid flow governing equation of multi-porous media. Our analysis of the experimental results shows that the threshold pressure gradient(TPG) of low and extra-low permeability reservoirs is excessively high, and does not conform to fluid flow through multi-porous media in the actual reservoir situation. Therefore, we present a reasonable TPG ranging from 0.006 to 0.04 MPa/m at the well depth of 1500 m and oil drainage distance of 500 m. The results of our study also indicate that the non-Darcy flow phenomenon will disappear when the TPG reaches a certain value. In addition, the TPG or non-Darcy flow in low and extra-low permeability reservoirs does not need to be considered in the productivity prediction and reservoir numerical simulation. At present, the black oil model or dual-porous media is suitable for simulating low and extra-low permeability reservoirs.
文摘For nonlinear coupled system of multilayer dynamics of fluids in porous media, the second order and first order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward, trod two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques, such as calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates, are adopted. Optimal order estimates in L2 norm are derived to determine the error in the second order approximate solution. This method has already been applied to the numerical simulation of migration-accumulation of oil resources.
文摘A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The flow is characterized by three parameters： /3 the ratio of radius to length of the arterial segment, Re the characteristic Reynolds number associated with the pressure outside the arterial segment and c the filtration coe^cient. The problem has been solved by the use of a perturbation technique, e is considered to be very small, ensuring the validity of the perturbation method. The computed numerical results are presented graphically to depict the variations in velocity, volumetric flow rate, wall shear stress and flow resistance.
