The design of a pressurized capillary rheometer operating at prescribed temperature is described to measure the viscosity of magnetic fluids （MFs） containing Fe3O4 magnetic nanoparticles （MNPs）. The equipment cons...The design of a pressurized capillary rheometer operating at prescribed temperature is described to measure the viscosity of magnetic fluids （MFs） containing Fe3O4 magnetic nanoparticles （MNPs）. The equipment constant of the rheometer was obtained using liquids with predetermined viscosities. Experimentally measured viscosities were used to evaluate different equations for suspension viscosities. Deviation of measured suspension viscosities from the Einstein equation was found to be basically due to the influence of spatial distribution and aggregation of Fe3O4 MNPs. By taking account of the coating layer on MNPs and the aggregation of MNPs in MFs, a modified Einstein equation was proposed to fit the experimental data. Moreover, the influence of external magnetic field on viscosity was also taken into account. Viscosities thus predicted are in good agreement with experimental data. Temperature effect on suspension viscosity was shown experimentally to be due to the shear-thinning behavior of the MFs.展开更多
This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame i...This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame images.The critical radius under different conditions was extracted using the image processing program.Combined with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured out.Moreover,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this work.The theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.展开更多
Nature inspired solutions enable biological systems to adapt and accomplish their tasks in very noisy and uncertain environments.Taking inspiration from nature,a novel bacteria controller capable of finding the source...Nature inspired solutions enable biological systems to adapt and accomplish their tasks in very noisy and uncertain environments.Taking inspiration from nature,a novel bacteria controller capable of finding the source of pollution in an underwatermedium turbulent environment is presented in this paper.Experiments prove that the controller is capable of performing pollutionsource exploration,pollution plume transverse and source declaration in a medium Peclet environment without distinctivelyseparating these three components as most researchers did.The results obtained from these experiments are considered asa step towards the deployment of robotic fish in a highly turbulent marine environment.Finally,a brief conclusion and futureextension are presented.展开更多
A new finite difference scheme-SCSD scheme has been proposed based on CD (Central Difference)scheme and SUD (Secondr-order Upwind Difference) scheme. Its basic feature is controIlable convectivesfability and always se...A new finite difference scheme-SCSD scheme has been proposed based on CD (Central Difference)scheme and SUD (Secondr-order Upwind Difference) scheme. Its basic feature is controIlable convectivesfability and always second-order accuracy (Stability-Controllable Second-order Difference ). It hasbeen proven that this scheme is convective-stable if the grid Peclet number .The advanage of this new scheme has been discussed based on the modified wavenumber analysis byusing Fourier transform. This scheme has been applied to the 2-D incompressible convective-diffusiveequation and 2-D compressible Euler equation, and corresponding finite difference equations have beenderived. Numerical examples of 1-D Burgers equation and 2-D transport equation have been presentedto show its good accuracy and controllable convective stability展开更多
The coagulation rate of a dilute polydisperse aerosol dispersion of particles is considered for small Peclet number, which provides a measure of the ratio of the relative sheareinduced motion to Brownian motion betWee...The coagulation rate of a dilute polydisperse aerosol dispersion of particles is considered for small Peclet number, which provides a measure of the ratio of the relative sheareinduced motion to Brownian motion betWeen two rigid spherical aerosol particles.The asymptotic form of the relative velocity of tWo unequal particles immerse in a simple shear flow when they are far apart is obtained.Using a singular pertllrbation method,a tWo term expansion for the dimensionless coagulation rate(Nusselt number) as function of the Peclet number is developed.In the limit of the radius of one of the two spheres becoming small,the result agrees with the dimensionless mass transfer rat6 to an aerosol particle at small Peclet number.展开更多
Heat flow in the Earth, from its hot interior to its relatively cool exterior, is the primary energy flow responsible for the dynamic nature of our planet. The motion of the plates excites a forced convective motion i...Heat flow in the Earth, from its hot interior to its relatively cool exterior, is the primary energy flow responsible for the dynamic nature of our planet. The motion of the plates excites a forced convective motion in the mantle, and this plate-driven mantle flow will strongly modulate the temperature field in the mantle because of the relatively high Peclet number of the mantle dynamic system. Here the role of the plate- driven mantle flow in the observed global heat flow is examined. The result reveals that the main feature of the distribution of the observed heat flow at the surface of the Earth matches well with the prediction and nearly one half of the average heat flow can be attributed to the thermal effect of the plate-driven mantle flow.展开更多
基金supported by the National Natural Science Foundation of China(NNSFC,Nos.20476065 and 20736004)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry,the State Key Laboratory of Multiphase Reaction of the Chinese Academy of Science(No.2003-5)the Key Laboratory of Organic Synthesis of Jiangsu Province,the Chemical Experiment Center of Soochow University and R&D Foundation of Nanjing Medical University(NY0586).
文摘The design of a pressurized capillary rheometer operating at prescribed temperature is described to measure the viscosity of magnetic fluids （MFs） containing Fe3O4 magnetic nanoparticles （MNPs）. The equipment constant of the rheometer was obtained using liquids with predetermined viscosities. Experimentally measured viscosities were used to evaluate different equations for suspension viscosities. Deviation of measured suspension viscosities from the Einstein equation was found to be basically due to the influence of spatial distribution and aggregation of Fe3O4 MNPs. By taking account of the coating layer on MNPs and the aggregation of MNPs in MFs, a modified Einstein equation was proposed to fit the experimental data. Moreover, the influence of external magnetic field on viscosity was also taken into account. Viscosities thus predicted are in good agreement with experimental data. Temperature effect on suspension viscosity was shown experimentally to be due to the shear-thinning behavior of the MFs.
基金supported by the National Natural Science Foundation of China(52106182,51888103)the National Science and Technology Major Project(2019-Ⅲ-0018-0062)+1 种基金supported by the State Key Laboratory of Clean Energy Utilization(Open Fund Project No.ZJUCEU2021016)Shaanxi Nature Science Foundation(No.2021JQ-265)。
文摘This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and n-decane.The experiment was carried out in a constant volume combustion bomb to get the flame images.The critical radius under different conditions was extracted using the image processing program.Combined with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured out.Moreover,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this work.The theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.
基金supported by European Union FP7 program,ICT-23 1 646,SHOAL
文摘Nature inspired solutions enable biological systems to adapt and accomplish their tasks in very noisy and uncertain environments.Taking inspiration from nature,a novel bacteria controller capable of finding the source of pollution in an underwatermedium turbulent environment is presented in this paper.Experiments prove that the controller is capable of performing pollutionsource exploration,pollution plume transverse and source declaration in a medium Peclet environment without distinctivelyseparating these three components as most researchers did.The results obtained from these experiments are considered asa step towards the deployment of robotic fish in a highly turbulent marine environment.Finally,a brief conclusion and futureextension are presented.
文摘A new finite difference scheme-SCSD scheme has been proposed based on CD (Central Difference)scheme and SUD (Secondr-order Upwind Difference) scheme. Its basic feature is controIlable convectivesfability and always second-order accuracy (Stability-Controllable Second-order Difference ). It hasbeen proven that this scheme is convective-stable if the grid Peclet number .The advanage of this new scheme has been discussed based on the modified wavenumber analysis byusing Fourier transform. This scheme has been applied to the 2-D incompressible convective-diffusiveequation and 2-D compressible Euler equation, and corresponding finite difference equations have beenderived. Numerical examples of 1-D Burgers equation and 2-D transport equation have been presentedto show its good accuracy and controllable convective stability
文摘The coagulation rate of a dilute polydisperse aerosol dispersion of particles is considered for small Peclet number, which provides a measure of the ratio of the relative sheareinduced motion to Brownian motion betWeen two rigid spherical aerosol particles.The asymptotic form of the relative velocity of tWo unequal particles immerse in a simple shear flow when they are far apart is obtained.Using a singular pertllrbation method,a tWo term expansion for the dimensionless coagulation rate(Nusselt number) as function of the Peclet number is developed.In the limit of the radius of one of the two spheres becoming small,the result agrees with the dimensionless mass transfer rat6 to an aerosol particle at small Peclet number.
基金Project supported by the National Natural Science Foundation of China (Grant No. 49774231).
文摘Heat flow in the Earth, from its hot interior to its relatively cool exterior, is the primary energy flow responsible for the dynamic nature of our planet. The motion of the plates excites a forced convective motion in the mantle, and this plate-driven mantle flow will strongly modulate the temperature field in the mantle because of the relatively high Peclet number of the mantle dynamic system. Here the role of the plate- driven mantle flow in the observed global heat flow is examined. The result reveals that the main feature of the distribution of the observed heat flow at the surface of the Earth matches well with the prediction and nearly one half of the average heat flow can be attributed to the thermal effect of the plate-driven mantle flow.
