This paper is concerned with the Navier-Stokes/Allen-Cahn system,which is used to model the dynamics of immiscible two-phase flows.We consider a 1D free boundary problem and assume that the viscosity coefficient depen...This paper is concerned with the Navier-Stokes/Allen-Cahn system,which is used to model the dynamics of immiscible two-phase flows.We consider a 1D free boundary problem and assume that the viscosity coefficient depends on the density in the form ofη(ρ)=ρ^(α).The existence of unique global H^(2m)-solutions(m∈N)to the free boundary problem is proven for when 0<α<1/4.Furthermore,we obtain the global C^(∞)-solutions if the initial data is smooth.展开更多
The influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel is investigated.The DarcyBrinkman model is used to characterize the fluid flow dyn...The influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel is investigated.The DarcyBrinkman model is used to characterize the fluid flow dynamics in porous materials.The analytical solutions are obtained for the unidirectional and completely developed flow.Based on a normal mode analysis,the generalized eigenvalue problem under a perturbed state is solved.The eigenvalue problem is then solved by the spectral method.Finally,the critical Rayleigh number with the corresponding wavenumber is evaluated at the assigned values of the other flow-governing parameters.The results show that increasing the Darcy number,the Lewis number,the Dufour parameter,or the Soret parameter increases the stability of the system,whereas increasing the inclination angle of the channel destabilizes the flow.Besides,the flow is the most unstable when the channel is vertically oriented.展开更多
To analyze the effects of a time-varying viscosity on the penetration length of grouting,in this study cement slur-ries with varying water-cement ratios have been investigated using the Bingham’sfluidflow equation and ...To analyze the effects of a time-varying viscosity on the penetration length of grouting,in this study cement slur-ries with varying water-cement ratios have been investigated using the Bingham’sfluidflow equation and a dis-crete element method.Afluid-solid coupling numerical model has been introduced accordingly,and its accuracy has been validated through comparison of theoretical and numerical solutions.For different fracture forms(a single fracture,a branch fracture,and a fracture network),the influence of the time-varying viscosity on the slurry length range has been investigated,considering the change in the fracture aperture.The results show that under different fracture forms and the same grouting process conditions,the influence of the time-varying viscosity on the seepage length is 0.350 m.展开更多
Fossil fuels cover around 80% of global energy consumption. However, the problems linked to their use justify the choice of using biofuel. In order to reduce as much as possible, diesel rate, an increase in the number...Fossil fuels cover around 80% of global energy consumption. However, the problems linked to their use justify the choice of using biofuel. In order to reduce as much as possible, diesel rate, an increase in the number of additives may be considered. Thus, in this work, the study of the used frying oil (UFO), bioethanol and diesel ternary system was undertaken. It emerges from this study that the addition of bioethanol reduces the viscosity and the density of the ternary system and permits a 90% substitution rate for diesel between the UFO and bioethanol. Finally, the percentage of oil becomes 40% after adding alcohol compared to the binary diesel crude vegetable oil mixture where this rate is 30%.展开更多
Mechanoreceptors play a vital role for animals to sense and monitor environmental parameters,like flow speed,tactile resistance,and pressure.The hairy-structured trichoid sensillum,a common type of mechanoreceptor in ...Mechanoreceptors play a vital role for animals to sense and monitor environmental parameters,like flow speed,tactile resistance,and pressure.The hairy-structured trichoid sensillum,a common type of mechanoreceptor in insects,is generally non-motile,embedded in a socket connected with cuticular substrate.However,we discover that the trichoid sensilla on the tongue of western bees(Apis mellifera L.)is rotatable and can be actively maneuvered by bees.The trichoid sensilla together with the socket base are mounted on the origami-like sheath of the tongue,and can rotate outwards along with the deformation of the tongue sheath.We illustrate that the rotation of the tongue sensilla hairs can locally generate shear force in the liquid to sense the viscosity,which may facilitate bees to adjust their feeding strategies.The viscosity sensitivity of the rotatable trichoid sensilla based on the origami-like mechanism,according to our mechanical model,is 13 times greater than that of the fixed sensilla.In addition,our finite element analysis shows that strain would concentrate on the trichoid sensilla base when rotating in the liquid,which may structurally enhance its perception sensitivity.This study reports a new mechanism of active mechanoreceptors and may have implications for origami mechanisms with correlative functional components,especially for micro-robotic systems used in underwater viscosity sensing.展开更多
Eighteen models based on two equations of state(EoS),three viscosity models,and four mixing rules were constructed to predict the viscosities of natural gases at high temperature and high pressure(HTHP)conditions.For ...Eighteen models based on two equations of state(EoS),three viscosity models,and four mixing rules were constructed to predict the viscosities of natural gases at high temperature and high pressure(HTHP)conditions.For pure substances,the parameters of free volume(FV)and entropy scaling(ES)models were found to scale with molecular weight,which indicates that the ordered behavior of parameters of Peng-Robinson(PR)and Perturbed-Chain Statistical Associating Fluid Theory(PC-SAFT)propagates to the behavior of parameters of viscosity model.Predicting the viscosities of natural gases showed that the FV and ES models respectively combined with MIX4 and MIX2 mixing rules produced the best accuracy.Moreover,the FV models were more accurate for predicting the viscosities of natural gases than ES models at HTHP conditions,while the ES models were superior to PRFT models.The average absolute relative deviations of the best accurate three models,i.e.,PC-SAFT-FV-MIX4,tPR-FVMIX4,and PC-SAFT-ES-MIX2,were 5.66%,6.27%,and 6.50%,respectively,which was available for industrial production.Compared with the existing industrial models(corresponding states theory and LBC),the proposed three models were more accurate for modeling the viscosity of natural gas,including gas condensate.展开更多
The low-reactivity mold flux with low SiO_(2)content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO_(2)in mold flux....The low-reactivity mold flux with low SiO_(2)content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO_(2)in mold flux.However,the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency.In this study,the co-addition of Li_(2)O and B_(2)O_(3)in CaO–Al_(2)O_(3)–10wt%Si O_(2)based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel,and the effect of Li_(2)O replacing B_(2)O_(3)on properties of mold flux was investigated.The viscosity of the mold flux with 2wt%Li_(2)O and 6wt%B_(2)O_(3)reached a minimum value of 0.07 Pa·s.The break temperature and melting point showed a similar trend with the viscosity.Besides,the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity.It demonstrated that with increasing Li_(2)O content in the mold flux from 0 to 6 wt%,the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li+released by Li_(2)O,indicating the added Li_(2)O was preferentially associated with Al^(3+)as a charge compensator.The precipitation of LiAlO_(2)crystalline phase gradually increased with the replacement of B_(2)O_(3)by Li_(2)O.Therefore,Li_(2)O content should be controlled below 2wt%to avoid LiAlO_(2)precipitation,which was harmful to the continuous casting of highaluminum steels.展开更多
Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the ...Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the oil viscosity. However, the relationship between the molecular composition of naphthenic acids and oil viscosity is not well understood. This study examined a “clean” heavy oil with low contents of heteroatoms but had a high content of naphthenic acids. Naphthenic acids were fractionated by distillation and caustic extraction. The molecular composition was characterized by high-resolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15–35 carbon atoms are dominant components of the acid fractions;the caustic extraction is capable of isolating naphthenic acids with less than 35 carbons, which is equivalent to the upper limit of the distillable components, but not those in the residue fraction;the total acid number of the heavy distillates is higher than that of the residue fraction;the viscosity of the distillation fraction increases exponentially with an increased boiling point of the distillates. Blending experiments indicates that there is a strong correlation between the oil viscosity and acids content, although the acid content is only a few percent of the total oil.展开更多
Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ de...Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.展开更多
Physics-informed neural networks(PINNs)are proved methods that are effective in solving some strongly nonlinear partial differential equations(PDEs),e.g.,Navier-Stokes equations,with a small amount of boundary or inte...Physics-informed neural networks(PINNs)are proved methods that are effective in solving some strongly nonlinear partial differential equations(PDEs),e.g.,Navier-Stokes equations,with a small amount of boundary or interior data.However,the feasibility of applying PINNs to the flow at moderate or high Reynolds numbers has rarely been reported.The present paper proposes an artificial viscosity(AV)-based PINN for solving the forward and inverse flow problems.Specifically,the AV used in PINNs is inspired by the entropy viscosity method developed in conventional computational fluid dynamics(CFD)to stabilize the simulation of flow at high Reynolds numbers.The newly developed PINN is used to solve the forward problem of the two-dimensional steady cavity flow at Re=1000 and the inverse problem derived from two-dimensional film boiling.The results show that the AV augmented PINN can solve both problems with good accuracy and substantially reduce the inference errors in the forward problem.展开更多
The process of transporting crude oil across pipelines is one of the most critical aspects of the midstream petroleum industry.In the present experimental work,the effect of temperature,pressure drop,and pipe diameter...The process of transporting crude oil across pipelines is one of the most critical aspects of the midstream petroleum industry.In the present experimental work,the effect of temperature,pressure drop,and pipe diameter on the flow rate of heavy crude oil have been assessed.Moreover,the total discharge and energy losses have been evaluated in order to demonstrate the improvements potentially achievable by using solar heating method replacing pipe,and adjusting the value of the initial pressure difference.Crude oil of API=20 has been used for the experiments,with the studied pipelines sections connecting the separator unit to the storage tank operating at a temperature of 25℃-100℃,pressure drop of 3,4,5,and 6 kg/cm^(2),and with pipe diameter of 4,6,and 8 in.The results show that on increasing the temperature and/or the pressure drop,the flow rate through the pipeline becomes higher,thus raising the total pumping energy(as the pipe diameter increase),while energy losses increase from the last separator to the storage tank in the field.A pipe diameter increase can also produce a growth of the total pumping energy(i.e.,energy losses increase).The results of the present analysis suggest that employing an optimal temperature(50℃)is needed to ensure good performance.展开更多
Geodetic observations have shown that there exist large differences in the viscosity of the deep lithosphere across many large strike-slip faults.Heterogeneity in lithospheric viscosity structure can influence the eff...Geodetic observations have shown that there exist large differences in the viscosity of the deep lithosphere across many large strike-slip faults.Heterogeneity in lithospheric viscosity structure can influence the efficiency of stress transfer and thus may have a significant effect on the earthquake cycle.Until now,how the lateral viscosity variation across strike-slip faults affects the earthquake cycles is still not well understood.Here,we investigate the effects of across-strike viscosity variation on long-term earthquake behaviors with a three-dimensional strike-slip fault model.Our model is a quasi-static model which is controlled by the slip-weakening friction law and powerlaw rheology.By comparing with the reference case,we find that low viscosity on one side of the fault results in a smaller rupture area but with a higher Coulomb stress drop on the ruptured fault region.In addition,low viscosity also leads to a small Coulomb stress accumulation rate.These combined effects increase the earthquake recurrence interval by approximately 10%and the earthquake moments by about 30%when the low viscosity is related to a geothermal gradient of 30 K/km.In addition,across-strike viscosity variation causes asymmetric interseismic ground surface deformation rate.As the viscosity contrast increases,the difference in the interseismic ground surface deformation rate between the two sides of the fault gradually increases,although the asymmetric feature is not pronounced.This asymmetry of interseismic ground deformation rate across a strike-slip fault is supposed to result in asymmetric coseismic deformation if the long-term plate motion velocity is invariant.As a result,this kind of asymmetry of interseismic deformation may influence the evaluation of potential earthquake hazards along large strike-slip faults with lateral viscosity contrast.展开更多
This paper studies the existence and uniqueness of local strong solutions to an Oldroyd-B model with density-dependent viscosity in a bounded domain Ω ⊂ R<sup>d</sup>, d = 2 or 3 via incompressible limit,...This paper studies the existence and uniqueness of local strong solutions to an Oldroyd-B model with density-dependent viscosity in a bounded domain Ω ⊂ R<sup>d</sup>, d = 2 or 3 via incompressible limit, in which the initial data is “well-prepared” and the velocity field enjoys the slip boundary conditions. The main idea is to derive the uniform energy estimates for nonlinear systems and corresponding incompressible limit.展开更多
In this paper, we study the viscosity solutions of the Neumann problem in a bounded C<sup>2</sup> domain Ω, where Δ<sup>N</sup>∞</sub> is called the normalized infinity Laplacian. The ...In this paper, we study the viscosity solutions of the Neumann problem in a bounded C<sup>2</sup> domain Ω, where Δ<sup>N</sup>∞</sub> is called the normalized infinity Laplacian. The normalized infinity Laplacian was first studied by Peres, Shramm, Sheffield and Wilson from the point of randomized theory named tug-of-war, which has wide applications in optimal mass transportation, financial option price problems, digital image processing, physical engineering, etc. We give the Lipschitz regularity of the viscosity solutions of the Neumann problem. The method we adopt is to choose suitable auxiliary functions as barrier functions and combine the perturbation method and viscosity solutions theory. .展开更多
Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D6821 and ASTM D2983...Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D6821 and ASTM D2983.Both tests are identical in the way they thermally condition the sample prior to viscosity measurement.While ASTM D2983 is cited in many current specifications,ASTM D6821 offers users and formulators a more accurate estimate of gear oil low temperature fluidity.The primary benefit in using ASTM D6821 is better precision.ASTM D6821 accomplishes this by automating the steps from prior to preheat through to viscosity measurement at end of test.展开更多
Based on the fluid motion equations, the physical meaning of eddy viscosity coefficient and the rationality of theBoussinesq hypothesis are discussed in this paper. The effect of the coefficient on numerical stability...Based on the fluid motion equations, the physical meaning of eddy viscosity coefficient and the rationality of theBoussinesq hypothesis are discussed in this paper. The effect of the coefficient on numerical stability is analyzed briefly.A semi-enclosed rectangular sea area, with an orthogonal spur dike, is applied in a 2-D numerical model to study the effect of horizontal eddy viscosity coefficient (AH). The computed result shows that AH has little influence on the tidal level and averaged flow velocity, but has obvious influence on the intensity and the range of return flow around near thespur dike. Correspondingly, a wind-driven current pool and an annular current are applied in a 3-D numerical modelrespectively to study the effect of vertical eddy viscosity coefficient (AV). The computed result shows that the absolute value of AV is inversely proportional to that of horizontal velocity, and the vertical gradient value of AV determines the ver-tical distribution of horizontal velocity. The distribution form of AV is theoretically recommended as a parabolic type, ofwhich the maximum value appears at 0.5 H.展开更多
We investigated the effect of Al2O3 content on the viscosity of CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3(mass ratio of CaO/SiO2 is 1.0,and Al2O3 content is 17wt%-29wt%)slags.The results show that the viscosity of the slag inc...We investigated the effect of Al2O3 content on the viscosity of CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3(mass ratio of CaO/SiO2 is 1.0,and Al2O3 content is 17wt%-29wt%)slags.The results show that the viscosity of the slag increases gradually with increases in the Al2O3 content in the range of 17wt%to 29wt%due to the role of Al2O3 as a network former in the polymerization of the aluminosilicate structure of the slag.With increases in the Al2O3 content from 17wt%to 29wt%,the apparent activation energy of the slags also increases from 180.85 to 210.23 kJ/mol,which is consistent with the variation in the critical temperature.The Fourier-transform infrared spectra indicate that the degree of polymerization of this slag is increased by the addition of Al2O3.The application of Iida’s model for predicting the slag viscosity in the presence of Cr2O3 indicates that the calculated viscosity values fit well with the measured values when both the temperature and Al2O3 content are at relatively low levels,i.e.,the temperature range of 1673 to 1803 K and the Al2O3 content range of 17wt%-29wt%in CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3 slag.展开更多
Based on the second viscosity, the local differential quadrature (LDQ) method is applied to solve shock tube problems. It is shown that it is necessary to consider the second viscosity to calculate shocks and to simul...Based on the second viscosity, the local differential quadrature (LDQ) method is applied to solve shock tube problems. It is shown that it is necessary to consider the second viscosity to calculate shocks and to simulate shock tubes based on the viscosity model. The roles of the shear viscous stress and the second viscous stress are checked. The results show that the viscosity model combined with the LDQ method can capture the main characteristics of shocks, and this technique is objective and simple.展开更多
The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces.An approximate method is used to obtain the solution of extensi...The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces.An approximate method is used to obtain the solution of extensional stress in closed form in the case of steady flow.For different internal viscosities,this parametric study shows different asymptotic regimes of the extensional viscosity as a function of strain rate.This analysis may explain the attenuation of pressure drop in strong flows from a phenom...展开更多
The Rheological behavior of semi-solid AZ91D at steady state is studied using a Couettetype viscometer in the present paper. The results show that the apparent viscosity ofsemi-solid AZ91D at the steady state increase...The Rheological behavior of semi-solid AZ91D at steady state is studied using a Couettetype viscometer in the present paper. The results show that the apparent viscosity ofsemi-solid AZ91D at the steady state increases with the solid fraction increasing, andgoes up sharply when the solid fraction reaches a certain value, which is called criticalfraction. In addition, the apparent viscosity of semi-solid AZ91D at the steady statetakes on a distinct downtrend with the shearing rate increasing, which indicates astrong shear thinning property. In addition, the critical solid fraction becomes higherunder larger shearing rate, owing to the more globular shape of the solid particles.Based on the present experiment results, an empirical equation is built as that, relatingthe steady state apparent viscosity of semi-solid AZ91D with the solid fraction fs andshearing rate γ at the same time: ηapp=10. 74exp(6.95fs)γ-0.86.展开更多
基金supported by the Key Project of the NSFC(12131010)the NSFC(11771155,12271032)+1 种基金the NSF of Guangdong Province(2021A1515010249,2021A1515010303)supported by the NSFC(11971179,12371205)。
文摘This paper is concerned with the Navier-Stokes/Allen-Cahn system,which is used to model the dynamics of immiscible two-phase flows.We consider a 1D free boundary problem and assume that the viscosity coefficient depends on the density in the form ofη(ρ)=ρ^(α).The existence of unique global H^(2m)-solutions(m∈N)to the free boundary problem is proven for when 0<α<1/4.Furthermore,we obtain the global C^(∞)-solutions if the initial data is smooth.
文摘The influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel is investigated.The DarcyBrinkman model is used to characterize the fluid flow dynamics in porous materials.The analytical solutions are obtained for the unidirectional and completely developed flow.Based on a normal mode analysis,the generalized eigenvalue problem under a perturbed state is solved.The eigenvalue problem is then solved by the spectral method.Finally,the critical Rayleigh number with the corresponding wavenumber is evaluated at the assigned values of the other flow-governing parameters.The results show that increasing the Darcy number,the Lewis number,the Dufour parameter,or the Soret parameter increases the stability of the system,whereas increasing the inclination angle of the channel destabilizes the flow.Besides,the flow is the most unstable when the channel is vertically oriented.
基金supported by the National Natural Science Foundation of China(Grant Numbers:U22A20234,42277170)the Key Research and Development Project of Hubei Province(Grant Number:2020BCB073).
文摘To analyze the effects of a time-varying viscosity on the penetration length of grouting,in this study cement slur-ries with varying water-cement ratios have been investigated using the Bingham’sfluidflow equation and a dis-crete element method.Afluid-solid coupling numerical model has been introduced accordingly,and its accuracy has been validated through comparison of theoretical and numerical solutions.For different fracture forms(a single fracture,a branch fracture,and a fracture network),the influence of the time-varying viscosity on the slurry length range has been investigated,considering the change in the fracture aperture.The results show that under different fracture forms and the same grouting process conditions,the influence of the time-varying viscosity on the seepage length is 0.350 m.
文摘Fossil fuels cover around 80% of global energy consumption. However, the problems linked to their use justify the choice of using biofuel. In order to reduce as much as possible, diesel rate, an increase in the number of additives may be considered. Thus, in this work, the study of the used frying oil (UFO), bioethanol and diesel ternary system was undertaken. It emerges from this study that the addition of bioethanol reduces the viscosity and the density of the ternary system and permits a 90% substitution rate for diesel between the UFO and bioethanol. Finally, the percentage of oil becomes 40% after adding alcohol compared to the binary diesel crude vegetable oil mixture where this rate is 30%.
基金The work is supported by the National Natural Science Foundation of China(grant No.52275298)the Shenzhen Science and Technology Program(Grant No.20220817165030002,and No.GXWD2021B03).
文摘Mechanoreceptors play a vital role for animals to sense and monitor environmental parameters,like flow speed,tactile resistance,and pressure.The hairy-structured trichoid sensillum,a common type of mechanoreceptor in insects,is generally non-motile,embedded in a socket connected with cuticular substrate.However,we discover that the trichoid sensilla on the tongue of western bees(Apis mellifera L.)is rotatable and can be actively maneuvered by bees.The trichoid sensilla together with the socket base are mounted on the origami-like sheath of the tongue,and can rotate outwards along with the deformation of the tongue sheath.We illustrate that the rotation of the tongue sensilla hairs can locally generate shear force in the liquid to sense the viscosity,which may facilitate bees to adjust their feeding strategies.The viscosity sensitivity of the rotatable trichoid sensilla based on the origami-like mechanism,according to our mechanical model,is 13 times greater than that of the fixed sensilla.In addition,our finite element analysis shows that strain would concentrate on the trichoid sensilla base when rotating in the liquid,which may structurally enhance its perception sensitivity.This study reports a new mechanism of active mechanoreceptors and may have implications for origami mechanisms with correlative functional components,especially for micro-robotic systems used in underwater viscosity sensing.
基金supported by the China Scholarship Council(No.202209225014)National Science Fund for Excellent Young Scholars(Grant No.52222402)+8 种基金National Natural Science Foundation of China(Grant No.52234003)National Natural Science Foundation of China(Grant No.52074235)National Science and Technology Major Project of China during the 13th Five-Year Plan Period(2016ZX05062)Sichuan Science and Technology Program(Grant No.2021YJ0345)National Natural Science Foundation of China(Grant No.51874251,51774243,52174036,and 51704247)Sichuan Science and Technology Program(NO.2022JDJQ0009)shale gas industry development Institute of Sichuan province,International S&T Cooperation Program of Sichuan Province(Grant No.2019YFH0169)the Deep Marine shale gas efficient development Overseas Expertise Introduction Center for Discipline Innovation(111 Center)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(No.2020CX020202,2020CX030202).
文摘Eighteen models based on two equations of state(EoS),three viscosity models,and four mixing rules were constructed to predict the viscosities of natural gases at high temperature and high pressure(HTHP)conditions.For pure substances,the parameters of free volume(FV)and entropy scaling(ES)models were found to scale with molecular weight,which indicates that the ordered behavior of parameters of Peng-Robinson(PR)and Perturbed-Chain Statistical Associating Fluid Theory(PC-SAFT)propagates to the behavior of parameters of viscosity model.Predicting the viscosities of natural gases showed that the FV and ES models respectively combined with MIX4 and MIX2 mixing rules produced the best accuracy.Moreover,the FV models were more accurate for predicting the viscosities of natural gases than ES models at HTHP conditions,while the ES models were superior to PRFT models.The average absolute relative deviations of the best accurate three models,i.e.,PC-SAFT-FV-MIX4,tPR-FVMIX4,and PC-SAFT-ES-MIX2,were 5.66%,6.27%,and 6.50%,respectively,which was available for industrial production.Compared with the existing industrial models(corresponding states theory and LBC),the proposed three models were more accurate for modeling the viscosity of natural gas,including gas condensate.
基金financially supported by the National Science Foundation China (No.U22A20171)the Scinence and Technology Program of Hebei,China (No.20311004D)。
文摘The low-reactivity mold flux with low SiO_(2)content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO_(2)in mold flux.However,the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency.In this study,the co-addition of Li_(2)O and B_(2)O_(3)in CaO–Al_(2)O_(3)–10wt%Si O_(2)based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel,and the effect of Li_(2)O replacing B_(2)O_(3)on properties of mold flux was investigated.The viscosity of the mold flux with 2wt%Li_(2)O and 6wt%B_(2)O_(3)reached a minimum value of 0.07 Pa·s.The break temperature and melting point showed a similar trend with the viscosity.Besides,the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity.It demonstrated that with increasing Li_(2)O content in the mold flux from 0 to 6 wt%,the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li+released by Li_(2)O,indicating the added Li_(2)O was preferentially associated with Al^(3+)as a charge compensator.The precipitation of LiAlO_(2)crystalline phase gradually increased with the replacement of B_(2)O_(3)by Li_(2)O.Therefore,Li_(2)O content should be controlled below 2wt%to avoid LiAlO_(2)precipitation,which was harmful to the continuous casting of highaluminum steels.
基金supported by the National Key R&D Program of China(2018YFA0702400)Science Foundation of China University of Petroleum,Beijing(ZX20210029).
文摘Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the oil viscosity. However, the relationship between the molecular composition of naphthenic acids and oil viscosity is not well understood. This study examined a “clean” heavy oil with low contents of heteroatoms but had a high content of naphthenic acids. Naphthenic acids were fractionated by distillation and caustic extraction. The molecular composition was characterized by high-resolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15–35 carbon atoms are dominant components of the acid fractions;the caustic extraction is capable of isolating naphthenic acids with less than 35 carbons, which is equivalent to the upper limit of the distillable components, but not those in the residue fraction;the total acid number of the heavy distillates is higher than that of the residue fraction;the viscosity of the distillation fraction increases exponentially with an increased boiling point of the distillates. Blending experiments indicates that there is a strong correlation between the oil viscosity and acids content, although the acid content is only a few percent of the total oil.
基金support provided by the National Science and Technology Major Project of the Ministry of Science and Technology of China(2016ZX05012-002-005)Shandong Provincial Natural Science Foundation(Grant no.:ZR2021QE051)+1 种基金National Natural Science Foundation of China(Grant no.:52206291)the Fundamental Research Funds for the Central Universities(Grant no.:22CX06030A).
文摘Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.
基金Project supported by the Fundamental Research Funds for the Central Universities of China(No.DUT21RC(3)063)the National Natural Science Foundation of China(No.51720105007)the Baidu Foundation(No.ghfund202202014542)。
文摘Physics-informed neural networks(PINNs)are proved methods that are effective in solving some strongly nonlinear partial differential equations(PDEs),e.g.,Navier-Stokes equations,with a small amount of boundary or interior data.However,the feasibility of applying PINNs to the flow at moderate or high Reynolds numbers has rarely been reported.The present paper proposes an artificial viscosity(AV)-based PINN for solving the forward and inverse flow problems.Specifically,the AV used in PINNs is inspired by the entropy viscosity method developed in conventional computational fluid dynamics(CFD)to stabilize the simulation of flow at high Reynolds numbers.The newly developed PINN is used to solve the forward problem of the two-dimensional steady cavity flow at Re=1000 and the inverse problem derived from two-dimensional film boiling.The results show that the AV augmented PINN can solve both problems with good accuracy and substantially reduce the inference errors in the forward problem.
文摘The process of transporting crude oil across pipelines is one of the most critical aspects of the midstream petroleum industry.In the present experimental work,the effect of temperature,pressure drop,and pipe diameter on the flow rate of heavy crude oil have been assessed.Moreover,the total discharge and energy losses have been evaluated in order to demonstrate the improvements potentially achievable by using solar heating method replacing pipe,and adjusting the value of the initial pressure difference.Crude oil of API=20 has been used for the experiments,with the studied pipelines sections connecting the separator unit to the storage tank operating at a temperature of 25℃-100℃,pressure drop of 3,4,5,and 6 kg/cm^(2),and with pipe diameter of 4,6,and 8 in.The results show that on increasing the temperature and/or the pressure drop,the flow rate through the pipeline becomes higher,thus raising the total pumping energy(as the pipe diameter increase),while energy losses increase from the last separator to the storage tank in the field.A pipe diameter increase can also produce a growth of the total pumping energy(i.e.,energy losses increase).The results of the present analysis suggest that employing an optimal temperature(50℃)is needed to ensure good performance.
基金supported by the National Natural Science Foundation of China (4207410592155204)the Joint Open Fund of Mengcheng National Geophysical Observatory (No. MENGO-202004)
文摘Geodetic observations have shown that there exist large differences in the viscosity of the deep lithosphere across many large strike-slip faults.Heterogeneity in lithospheric viscosity structure can influence the efficiency of stress transfer and thus may have a significant effect on the earthquake cycle.Until now,how the lateral viscosity variation across strike-slip faults affects the earthquake cycles is still not well understood.Here,we investigate the effects of across-strike viscosity variation on long-term earthquake behaviors with a three-dimensional strike-slip fault model.Our model is a quasi-static model which is controlled by the slip-weakening friction law and powerlaw rheology.By comparing with the reference case,we find that low viscosity on one side of the fault results in a smaller rupture area but with a higher Coulomb stress drop on the ruptured fault region.In addition,low viscosity also leads to a small Coulomb stress accumulation rate.These combined effects increase the earthquake recurrence interval by approximately 10%and the earthquake moments by about 30%when the low viscosity is related to a geothermal gradient of 30 K/km.In addition,across-strike viscosity variation causes asymmetric interseismic ground surface deformation rate.As the viscosity contrast increases,the difference in the interseismic ground surface deformation rate between the two sides of the fault gradually increases,although the asymmetric feature is not pronounced.This asymmetry of interseismic ground deformation rate across a strike-slip fault is supposed to result in asymmetric coseismic deformation if the long-term plate motion velocity is invariant.As a result,this kind of asymmetry of interseismic deformation may influence the evaluation of potential earthquake hazards along large strike-slip faults with lateral viscosity contrast.
文摘This paper studies the existence and uniqueness of local strong solutions to an Oldroyd-B model with density-dependent viscosity in a bounded domain Ω ⊂ R<sup>d</sup>, d = 2 or 3 via incompressible limit, in which the initial data is “well-prepared” and the velocity field enjoys the slip boundary conditions. The main idea is to derive the uniform energy estimates for nonlinear systems and corresponding incompressible limit.
文摘In this paper, we study the viscosity solutions of the Neumann problem in a bounded C<sup>2</sup> domain Ω, where Δ<sup>N</sup>∞</sub> is called the normalized infinity Laplacian. The normalized infinity Laplacian was first studied by Peres, Shramm, Sheffield and Wilson from the point of randomized theory named tug-of-war, which has wide applications in optimal mass transportation, financial option price problems, digital image processing, physical engineering, etc. We give the Lipschitz regularity of the viscosity solutions of the Neumann problem. The method we adopt is to choose suitable auxiliary functions as barrier functions and combine the perturbation method and viscosity solutions theory. .
文摘Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D6821 and ASTM D2983.Both tests are identical in the way they thermally condition the sample prior to viscosity measurement.While ASTM D2983 is cited in many current specifications,ASTM D6821 offers users and formulators a more accurate estimate of gear oil low temperature fluidity.The primary benefit in using ASTM D6821 is better precision.ASTM D6821 accomplishes this by automating the steps from prior to preheat through to viscosity measurement at end of test.
文摘Based on the fluid motion equations, the physical meaning of eddy viscosity coefficient and the rationality of theBoussinesq hypothesis are discussed in this paper. The effect of the coefficient on numerical stability is analyzed briefly.A semi-enclosed rectangular sea area, with an orthogonal spur dike, is applied in a 2-D numerical model to study the effect of horizontal eddy viscosity coefficient (AH). The computed result shows that AH has little influence on the tidal level and averaged flow velocity, but has obvious influence on the intensity and the range of return flow around near thespur dike. Correspondingly, a wind-driven current pool and an annular current are applied in a 3-D numerical modelrespectively to study the effect of vertical eddy viscosity coefficient (AV). The computed result shows that the absolute value of AV is inversely proportional to that of horizontal velocity, and the vertical gradient value of AV determines the ver-tical distribution of horizontal velocity. The distribution form of AV is theoretically recommended as a parabolic type, ofwhich the maximum value appears at 0.5 H.
基金This work was financially supported by the Fundamental Research Funds for the Central Universities of China(Nos.FRF-TP-20-048A2 and FRF-AT-20-02).
文摘We investigated the effect of Al2O3 content on the viscosity of CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3(mass ratio of CaO/SiO2 is 1.0,and Al2O3 content is 17wt%-29wt%)slags.The results show that the viscosity of the slag increases gradually with increases in the Al2O3 content in the range of 17wt%to 29wt%due to the role of Al2O3 as a network former in the polymerization of the aluminosilicate structure of the slag.With increases in the Al2O3 content from 17wt%to 29wt%,the apparent activation energy of the slags also increases from 180.85 to 210.23 kJ/mol,which is consistent with the variation in the critical temperature.The Fourier-transform infrared spectra indicate that the degree of polymerization of this slag is increased by the addition of Al2O3.The application of Iida’s model for predicting the slag viscosity in the presence of Cr2O3 indicates that the calculated viscosity values fit well with the measured values when both the temperature and Al2O3 content are at relatively low levels,i.e.,the temperature range of 1673 to 1803 K and the Al2O3 content range of 17wt%-29wt%in CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3 slag.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 50921001)the National Basic Research Program of China (973Program) (No. 2010CB832700)
文摘Based on the second viscosity, the local differential quadrature (LDQ) method is applied to solve shock tube problems. It is shown that it is necessary to consider the second viscosity to calculate shocks and to simulate shock tubes based on the viscosity model. The roles of the shear viscous stress and the second viscous stress are checked. The results show that the viscosity model combined with the LDQ method can capture the main characteristics of shocks, and this technique is objective and simple.
基金supported by the National Natural Science Foundation of China (No.10702045).
文摘The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces.An approximate method is used to obtain the solution of extensional stress in closed form in the case of steady flow.For different internal viscosities,this parametric study shows different asymptotic regimes of the extensional viscosity as a function of strain rate.This analysis may explain the attenuation of pressure drop in strong flows from a phenom...
基金The present study was supported by the National Key Basic Research and Development Programme of China (Project No. G2000067202).
文摘The Rheological behavior of semi-solid AZ91D at steady state is studied using a Couettetype viscometer in the present paper. The results show that the apparent viscosity ofsemi-solid AZ91D at the steady state increases with the solid fraction increasing, andgoes up sharply when the solid fraction reaches a certain value, which is called criticalfraction. In addition, the apparent viscosity of semi-solid AZ91D at the steady statetakes on a distinct downtrend with the shearing rate increasing, which indicates astrong shear thinning property. In addition, the critical solid fraction becomes higherunder larger shearing rate, owing to the more globular shape of the solid particles.Based on the present experiment results, an empirical equation is built as that, relatingthe steady state apparent viscosity of semi-solid AZ91D with the solid fraction fs andshearing rate γ at the same time: ηapp=10. 74exp(6.95fs)γ-0.86.
