A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil ...A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil under moving bed conditions and surrounding terrain changes.Moreover,the weakly compressible smoothed particle hydrodynamics(WCSPH)approach has been exploited to simulate the instability process of the free surfacefluid and its propagation characteristics at the solid–liquid interface.The influence of a suspended medium on the waterflow dynamics has been characterized using the mixed viscosity concept accounting for the solid–liquid mixed particle volume ratio.Numerical simulations of wall-jet scouring and reservoir sedimentflushing on a mobile bed were performed and validated with experiments.The results show that the proposed WCSPH–DEM coupling model is highly suitable for determining parameters,such as the local maximum scour depth,the scour pit width,and the sand bed profile.The effects on the hydraulic erosion process of two important para-meters of the mixed viscosity coefficient(initial solid volume concentration and initial viscosity coefficient)are also discussed to a certain extent in this study.展开更多
The content and distributive feature of oil in Meizhou Bay, China during summer were analysed on the basis of water quality survey. The result showed that oil concentration ranges between 5—51 μg/dm 3 with an avera...The content and distributive feature of oil in Meizhou Bay, China during summer were analysed on the basis of water quality survey. The result showed that oil concentration ranges between 5—51 μg/dm 3 with an average of 19 8 μg/dm 3. The mixed coefficient is lower. The difference of oil distribution between high tide and low tide is related to the distribution of land pollution and is mainly decided by water dynamics. Average turn over rate and enrichment coefficient can provide fundamental information to estimate oil concentration in sea water.展开更多
A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and mu...A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.展开更多
The model for computing frictional coefficient between two teeth faces at the state of mixed elastohydrodynamic lubrication is established. And then more than 80 sets of numerical calculations and six sets of disc fat...The model for computing frictional coefficient between two teeth faces at the state of mixed elastohydrodynamic lubrication is established. And then more than 80 sets of numerical calculations and six sets of disc fatigue tests are completed. The results show that when the film thickness ratio λ 〈1.6, frictional coefficient μ is drastically decreased as λ. rises; Thereafter it decreases smoothly until λ=4.5. When λ〉4.5, however, it goes up again with λ, which indicates that the excessive film thickness ratio will deteriorate gearing contact fatigue strength. At the end, the formulae for determining the frictional coefficients are formed.展开更多
Transverse mixing characteristics of solute in the open channel flow can provide useful information for river environmental management. The lateral mixing coefficient is a crucial parameter for reproducing the transve...Transverse mixing characteristics of solute in the open channel flow can provide useful information for river environmental management. The lateral mixing coefficient is a crucial parameter for reproducing the transverse mixing either by numerical simulation or by analytical prediction. Since the solute mixing can be greatly affected by the lateral variations in water depth, mixing coefficient should be determined in each sub-section (i.e., the main channel, side slope and flood plain) separately. In this article, the transverse mixing in a symmetric trapezoidal compound channel was studied based on laboratory measurement of longitudinal and transverse velocity components and lateral distribution of solute concentration. The lateral mixing coefficient was estimated by adopting different Schmidt numbers in different sub-sections divided according to the developing trend of the eddy viscosity, and finally a piecewise linear profile of mixing coefficient was adopted to analytically predict the transverse solute concentration. The comparison between the analytically predicted data and the measuring solute concentration proved that this is an effective way to estimate the lateral mixing in the open channel flow with lateral variations in water depth,展开更多
In this study, discrete element method (DEM) was employed to simulate the movement of non-cohesive mono-dispersed particles in a V-blender along with particle-particle and particle-boundary interactions. To validate...In this study, discrete element method (DEM) was employed to simulate the movement of non-cohesive mono-dispersed particles in a V-blender along with particle-particle and particle-boundary interactions. To validate the model, DEM results were successfully compared to positron emission particle tracking (PEPT) data reported in literature. The validated model was then utilized to explore the effects of rotational speed and fill level on circulation intensity and axial dispersion coefficient of non-cohesive particles in the V-blender. The results showed that the circulation intensity increased with an increase in the rotational speed from 15 to 60 rpm. As the fill level increased from 20% to 46%, the circulation intensity decreased, reached its minimum value at a fill level of 34% for all rotational speeds, and did not change significantly at fill levels greater than 34%. The DEM results also revealed that the axial dispersion coefficient of particles in the V-blender was a linear function of the rotational speed. These trends were in good agreement with the experimentallv determined values reported bv previous researchers.展开更多
基金funded by the National Natural Science Foundation of China(No.51568022)the Science and Technology Project of Education Department,Jiangxi Province,China(No.GJJ217404).
文摘A complex interface exists between waterflow and solid particles during hydraulic soil erosion.In this study,the particle discrete element method(DEM)has been used to simulate the hydraulic erosion of a granular soil under moving bed conditions and surrounding terrain changes.Moreover,the weakly compressible smoothed particle hydrodynamics(WCSPH)approach has been exploited to simulate the instability process of the free surfacefluid and its propagation characteristics at the solid–liquid interface.The influence of a suspended medium on the waterflow dynamics has been characterized using the mixed viscosity concept accounting for the solid–liquid mixed particle volume ratio.Numerical simulations of wall-jet scouring and reservoir sedimentflushing on a mobile bed were performed and validated with experiments.The results show that the proposed WCSPH–DEM coupling model is highly suitable for determining parameters,such as the local maximum scour depth,the scour pit width,and the sand bed profile.The effects on the hydraulic erosion process of two important para-meters of the mixed viscosity coefficient(initial solid volume concentration and initial viscosity coefficient)are also discussed to a certain extent in this study.
文摘The content and distributive feature of oil in Meizhou Bay, China during summer were analysed on the basis of water quality survey. The result showed that oil concentration ranges between 5—51 μg/dm 3 with an average of 19 8 μg/dm 3. The mixed coefficient is lower. The difference of oil distribution between high tide and low tide is related to the distribution of land pollution and is mainly decided by water dynamics. Average turn over rate and enrichment coefficient can provide fundamental information to estimate oil concentration in sea water.
基金supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA014200)the National Natural Science Foundation of China(No.11444001)the Municipal Natural Science Foundation of Tianjin(No.14JCYBJC16500)
文摘A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.
基金This project is supported by Provincial Natural Science Foundation of Shanxi, China (No. 20041057)Scholarship Council of Shanxi, China (No. 2005-22)
文摘The model for computing frictional coefficient between two teeth faces at the state of mixed elastohydrodynamic lubrication is established. And then more than 80 sets of numerical calculations and six sets of disc fatigue tests are completed. The results show that when the film thickness ratio λ 〈1.6, frictional coefficient μ is drastically decreased as λ. rises; Thereafter it decreases smoothly until λ=4.5. When λ〉4.5, however, it goes up again with λ, which indicates that the excessive film thickness ratio will deteriorate gearing contact fatigue strength. At the end, the formulae for determining the frictional coefficients are formed.
基金the National Natural Science Foundation of China (Grant Nos. 50679061, 50709025)the Open Fund of State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China (Grant No. Lp0601).
文摘Transverse mixing characteristics of solute in the open channel flow can provide useful information for river environmental management. The lateral mixing coefficient is a crucial parameter for reproducing the transverse mixing either by numerical simulation or by analytical prediction. Since the solute mixing can be greatly affected by the lateral variations in water depth, mixing coefficient should be determined in each sub-section (i.e., the main channel, side slope and flood plain) separately. In this article, the transverse mixing in a symmetric trapezoidal compound channel was studied based on laboratory measurement of longitudinal and transverse velocity components and lateral distribution of solute concentration. The lateral mixing coefficient was estimated by adopting different Schmidt numbers in different sub-sections divided according to the developing trend of the eddy viscosity, and finally a piecewise linear profile of mixing coefficient was adopted to analytically predict the transverse solute concentration. The comparison between the analytically predicted data and the measuring solute concentration proved that this is an effective way to estimate the lateral mixing in the open channel flow with lateral variations in water depth,
基金The financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC)
文摘In this study, discrete element method (DEM) was employed to simulate the movement of non-cohesive mono-dispersed particles in a V-blender along with particle-particle and particle-boundary interactions. To validate the model, DEM results were successfully compared to positron emission particle tracking (PEPT) data reported in literature. The validated model was then utilized to explore the effects of rotational speed and fill level on circulation intensity and axial dispersion coefficient of non-cohesive particles in the V-blender. The results showed that the circulation intensity increased with an increase in the rotational speed from 15 to 60 rpm. As the fill level increased from 20% to 46%, the circulation intensity decreased, reached its minimum value at a fill level of 34% for all rotational speeds, and did not change significantly at fill levels greater than 34%. The DEM results also revealed that the axial dispersion coefficient of particles in the V-blender was a linear function of the rotational speed. These trends were in good agreement with the experimentallv determined values reported bv previous researchers.