A coupled numerical method for the direct numerical simulation of particle-fluid systems is formulated and implemented, resolving an order of magnitude smaller than particle size. The particle motion is described by t...A coupled numerical method for the direct numerical simulation of particle-fluid systems is formulated and implemented, resolving an order of magnitude smaller than particle size. The particle motion is described by the time-driven hard-sphere model, while the hydrodynamic equations governing fluid flow are solved by the lattice Boltzmann method （LBM）, Particle-fluid coupling is realized by an immersed boundary method （IBM）, which considers the effect of boundary on surrounding fluid as a restoring force added to the governing equations of the fluid. The proposed scheme is validated in the classical flow-around-cylinder simulations, and preliminary application of this scheme to fluidization is reported, demonstrating it to be a promising computational strategy for better understanding complex behavior in particle-fluid systems.展开更多
Ion mobility spectra for ten alcohols have been studied in an ion mobility spectrometry apparatus equipped with a corona discharge ionization source. Using protonated water cluster ions as the reactant ions and clean ...Ion mobility spectra for ten alcohols have been studied in an ion mobility spectrometry apparatus equipped with a corona discharge ionization source. Using protonated water cluster ions as the reactant ions and clean air as the drift gas, the alcohols exhibit different product ion characteristic peaks in their ion mobility spectra. The detection limit for these alcohols is at low concentration pmol/L level according to the concentration calibration by exponential dilution method. Based on the measured ion mobilities, several chemical physics parameters of the ion-molecular interaction at atmosphere were obtained, including the ionic collision cross sections, diffusion coefficients, collision rate constants, and the ionic radii under the hard-sphere model approximation.展开更多
Ionic liquids(ILs),recognized as environmentally friendly green reagents,have good application prospects in many fields.However,their high viscosity has hindered their widespread application.Currently,an effective sol...Ionic liquids(ILs),recognized as environmentally friendly green reagents,have good application prospects in many fields.However,their high viscosity has hindered their widespread application.Currently,an effective solution is to introduce a solvent as an additive.In this work,ethanol with different molar fractions was chosen to form working pairs with three ILs([emim]BF4,[bmim]BF4 and[hmim]BF4),to reduce their viscosities.The densities and viscosities of the three working pairs were obtained in a temperature range of 293.15 to 338.15 K,thereby determining the thermal expansion coefficients.The effects of ethanol on the volumetric and viscometric characteristics of the three ILs are discussed.To further analyze the interactions between ethanol and the ILs,excess mole volume and viscosity deviations were introduced.The interactions between different molecules were stronger than those between the same molecules in the working pairs.This is the main reason why the addition of ethanol reduces the viscosity of the three ILs.Finally,the hard-sphere model was applied to predict the viscosities of the working pairs.Upon introducing an adjustable argument,the average absolute relative deviation of the prediction for the aforementioned three ILs decreased to 4.4%,5.9%,and 5.0%,respectively.展开更多
Fully resolved simulations of particulate and aggregative fluidization systems are performed suc-cessfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model （LBM-TDHS）. In this m...Fully resolved simulations of particulate and aggregative fluidization systems are performed suc-cessfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model （LBM-TDHS）. In this method, the discrete particle phase is described by time-driven hard-sphere model, and the governing equations of the continuous fluid phase are solved with lattice Boltz-mann method. Particle-fluid coupling is implemented by immersed moving boundary method. Time averaged flow structure of the simulated results show the formation of core-annulus structure and sigmoid distribution of voidage in the axial direction, which are typical phenomena in fluidization systems. Combining the results of the simulation, the energy consumption Nst for suspending and transporting solids is calculated from the direct numerical simulation （DNS） of fluidization, and the stability criterion Nst/NT = rain proposed in EMMS/bubbling model is verified numerically. Further-more the numerical results show that the value of Nst/NT in particulate fiuidization is much higher than that in aggregative fluidization, but Nst/NT = rain is effective for both particulate and aggregative fluidization.展开更多
基金sponsored by Ministry of Finance under the grant ZDYZ2008-2National Key Science and Technology Project under the grant 2008ZX05014-003-006HZthe Chinese Academy of Sciences under the grant KGCX2-YW-124
文摘A coupled numerical method for the direct numerical simulation of particle-fluid systems is formulated and implemented, resolving an order of magnitude smaller than particle size. The particle motion is described by the time-driven hard-sphere model, while the hydrodynamic equations governing fluid flow are solved by the lattice Boltzmann method （LBM）, Particle-fluid coupling is realized by an immersed boundary method （IBM）, which considers the effect of boundary on surrounding fluid as a restoring force added to the governing equations of the fluid. The proposed scheme is validated in the classical flow-around-cylinder simulations, and preliminary application of this scheme to fluidization is reported, demonstrating it to be a promising computational strategy for better understanding complex behavior in particle-fluid systems.
基金V. ACKNOWLEDGMENTS This work was support by the National Natural Science Foundation of China （No.20577049, No.20707025, and No.20907054）, the Chinese-Slovak Scientific and Technological Cooperation Project （No.4-03）, the Excellent Youth Foundation of Anhui Province Scientific Committee （No.06045098）, the Hefei Institutes of Physical Science, Chinese Academy of Science are gratefully acknowledged, and the Slovak Research and Development Agency, projects （No.LPP-0143-06 and No.SK- CN-029-07）.
文摘Ion mobility spectra for ten alcohols have been studied in an ion mobility spectrometry apparatus equipped with a corona discharge ionization source. Using protonated water cluster ions as the reactant ions and clean air as the drift gas, the alcohols exhibit different product ion characteristic peaks in their ion mobility spectra. The detection limit for these alcohols is at low concentration pmol/L level according to the concentration calibration by exponential dilution method. Based on the measured ion mobilities, several chemical physics parameters of the ion-molecular interaction at atmosphere were obtained, including the ionic collision cross sections, diffusion coefficients, collision rate constants, and the ionic radii under the hard-sphere model approximation.
基金funded by the National Natural Science Foundation of China(Grant No.:51976166)。
文摘Ionic liquids(ILs),recognized as environmentally friendly green reagents,have good application prospects in many fields.However,their high viscosity has hindered their widespread application.Currently,an effective solution is to introduce a solvent as an additive.In this work,ethanol with different molar fractions was chosen to form working pairs with three ILs([emim]BF4,[bmim]BF4 and[hmim]BF4),to reduce their viscosities.The densities and viscosities of the three working pairs were obtained in a temperature range of 293.15 to 338.15 K,thereby determining the thermal expansion coefficients.The effects of ethanol on the volumetric and viscometric characteristics of the three ILs are discussed.To further analyze the interactions between ethanol and the ILs,excess mole volume and viscosity deviations were introduced.The interactions between different molecules were stronger than those between the same molecules in the working pairs.This is the main reason why the addition of ethanol reduces the viscosity of the three ILs.Finally,the hard-sphere model was applied to predict the viscosities of the working pairs.Upon introducing an adjustable argument,the average absolute relative deviation of the prediction for the aforementioned three ILs decreased to 4.4%,5.9%,and 5.0%,respectively.
基金supported by the National Natural Science Foundation of China under Grant No.21106155the Chinese Academy of Sciences under Grant No.XDA07080303
文摘Fully resolved simulations of particulate and aggregative fluidization systems are performed suc-cessfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model （LBM-TDHS）. In this method, the discrete particle phase is described by time-driven hard-sphere model, and the governing equations of the continuous fluid phase are solved with lattice Boltz-mann method. Particle-fluid coupling is implemented by immersed moving boundary method. Time averaged flow structure of the simulated results show the formation of core-annulus structure and sigmoid distribution of voidage in the axial direction, which are typical phenomena in fluidization systems. Combining the results of the simulation, the energy consumption Nst for suspending and transporting solids is calculated from the direct numerical simulation （DNS） of fluidization, and the stability criterion Nst/NT = rain proposed in EMMS/bubbling model is verified numerically. Further-more the numerical results show that the value of Nst/NT in particulate fiuidization is much higher than that in aggregative fluidization, but Nst/NT = rain is effective for both particulate and aggregative fluidization.
