With the self-made equipment, the benavior of the splashed slag coating was studied by the thermo-simulation. The influenceof TFe, basicity and heating rate of slag on the occurrence of fractional melting was investig...With the self-made equipment, the benavior of the splashed slag coating was studied by the thermo-simulation. The influenceof TFe, basicity and heating rate of slag on the occurrence of fractional melting was investigated. Furthermore, the composition variationof slag in different stages of the heating process was also discussed, and the mechanism of fractional me1ting was explained. In addition,the exploitation of this phenomenon in practice was also discussed.展开更多
“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigan...“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigantic splashes(落水声)which eventually turned into thick mists.Liu,holding his breath,clicked the shutter quickly to capture the grandeur of the Hukou Waterfall,the largest waterfall on the Yellow River.展开更多
Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions ...Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions.A numerical model of multi-particle SLD coupling breaking,bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size.The results show that the peak value of droplet collection efficiencyβdecreases due to splashing.The bounce phenomenon will make the impact limit S_(m)of the water drops decrease.With the increase of the SLD particle size,the water drop bounce point gradually moves toward the trailing edge of the wing.The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100μm.When the SLD particle size increases,the height of the water droplet shelter zone on the upper edge of the wing gradually decreases,and the velocity in the Y direction decreases first and then increases in the opposite direction,increasing the probability of SLD hitting the wing again.Large particle droplets have a higher effect on the impact limit S_(m)than smaller droplets.Therefore,in the numerical simulation of the SLD operating conditions,it is very important to ensure the proportion of large particle size water droplets.展开更多
In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the ...In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.展开更多
The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essenti...The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.展开更多
To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone mo...To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.展开更多
The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at th...The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.展开更多
This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect...This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.展开更多
This study determined that the range of the marine splash zone (MSZ) of China’s Qingdao,Zhoushan. Xiamen. Zhanjiang harbour area was about 0-2.4 m above the mean high water level (MHWL) of the seawater that the MSZ c...This study determined that the range of the marine splash zone (MSZ) of China’s Qingdao,Zhoushan. Xiamen. Zhanjiang harbour area was about 0-2.4 m above the mean high water level (MHWL) of the seawater that the MSZ corrosion peak (MSZCP) was usually 0.6- 1.2 m above the MHWL. and was caused by the large salt particle accumulation on the A3 carbon steel test sample surface and by the high frequency altemations of wet and dry environmental conditions around the samples.展开更多
Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spe...Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive spectrometry and scanning electron microscopy. Corrosion resistance of the rust films was demonstrated by the electrochemical impedance spectroscopy. The wettability of the steel surface was calculated from the data conceruing the wetting degree and the conductivity. The results showed that, in the initial stage, the products of the outer rust layer were mainly made up of Fe（Ⅲ） oxyhydroxide, while the main component of the inner rust layer was magnetite. With an increase in the corrosion time, the inner rust layer continuously turned into the outer rust layer. In addition, both rust layers became dense, thus playing a protective role with respect to matrix. The existence of the rust layer significantly prolonged the residence time of the seawater on the sample surface, a result that tends to improve the cathodic protection effect for steel structures exposed to marine splash zones.展开更多
文摘With the self-made equipment, the benavior of the splashed slag coating was studied by the thermo-simulation. The influenceof TFe, basicity and heating rate of slag on the occurrence of fractional melting was investigated. Furthermore, the composition variationof slag in different stages of the heating process was also discussed, and the mechanism of fractional me1ting was explained. In addition,the exploitation of this phenomenon in practice was also discussed.
文摘“It's coming!”Liu Fuhai shouted,lying prone on a rock,one of his eyes pressed against his camera.Beads of sweat could be seen on his forehead.Roaring water in the Yellow River plunged from the cliff,making gigantic splashes(落水声)which eventually turned into thick mists.Liu,holding his breath,clicked the shutter quickly to capture the grandeur of the Hukou Waterfall,the largest waterfall on the Yellow River.
基金supported in part by the National Natural Science Foundation of China(No.52276009)。
文摘Accurate simulation of ice accretion of supercooled large droplet(SLD)is pivotal for the international airworthiness certification of large aircraft.Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions.A numerical model of multi-particle SLD coupling breaking,bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size.The results show that the peak value of droplet collection efficiencyβdecreases due to splashing.The bounce phenomenon will make the impact limit S_(m)of the water drops decrease.With the increase of the SLD particle size,the water drop bounce point gradually moves toward the trailing edge of the wing.The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100μm.When the SLD particle size increases,the height of the water droplet shelter zone on the upper edge of the wing gradually decreases,and the velocity in the Y direction decreases first and then increases in the opposite direction,increasing the probability of SLD hitting the wing again.Large particle droplets have a higher effect on the impact limit S_(m)than smaller droplets.Therefore,in the numerical simulation of the SLD operating conditions,it is very important to ensure the proportion of large particle size water droplets.
基金supported by the Independent Research and Development Projects of State Key Laboratory of Heavy Duty AC Drive Electric Locomotive Systems Integration(No.R111720H01385),China.
文摘In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.
基金the Applied Basic Research Project of Yunnan Province,China(No.202301 AT070411).
文摘The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.
基金Supported by the Guangdong Provincial Natural Science Foundation of China under Grant No.2021A1515011917the National Natural Science Foundation of China under Grant No.52371344 and U22A2012+1 种基金Fundamental Research Funds for the Central Universities,Sun Yat-sen University under Grant No.22qntd0601the start-up funding to Y.J.from Sun Yat-sen University.
文摘To explore the water entry flow and impact load characteristics of northern gannets,we conducted water entry experiments using a northern gannet’s head model based on three-dimensional(3D)printing and several cone models under different Froude numbers.A high-speed camera was used to capture flow images,and an inertial measurement unit(IMU)was used to record the water entry impact loads.The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load.Specifically,the northern gannet’s head model created a smaller water entry splash crown,cavity geometry,and impact load compared with the cone models of similar sizes.
基金supported by the Na‑tional Natural Science Foundation of China(No.52075241)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronau‑tics and Astronautics)(Nos.HTL-A-22K04 and HTL-O21G13).
文摘The intermediate gearbox of a helicopter operates under splash lubrication.If the bearing produces metal particles due to insufficient lubrication or wear,whether it can be adsorbed by the metal particles signal at the bottom of the gearbox and alarm directly affects the flight safety of the helicopter.Based on the CFD method,the factors affecting the accessibility of metal particles are analyzed by using the volume of fluid-discrete phase model(VOFDPM)coupling model,the RNG k-ɛturbulence model and the dynamic grid technology.Furthermore,the optimization research on the casing structure is conducted.Experimental results show that the accessibility of metal particles is optimal when the gear speed is 6000 rad/min or the immersion depth is 24 mm.The density of metal particles exhibits a nonlinear relationship with their accessibility,and the particle size has a relatively small impact on their accessibility without an order of magnitude change.
基金Supported by the National Natural Science Foundation of China (NSFC) (No. 41101019)the Fundamental Research Funds for the Central Universities of Chinathe State Key Laboratory of Earth Surface Processes and Resource Ecology of China (No. 2011-KF-09)
文摘This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.
文摘This study determined that the range of the marine splash zone (MSZ) of China’s Qingdao,Zhoushan. Xiamen. Zhanjiang harbour area was about 0-2.4 m above the mean high water level (MHWL) of the seawater that the MSZ corrosion peak (MSZCP) was usually 0.6- 1.2 m above the MHWL. and was caused by the large salt particle accumulation on the A3 carbon steel test sample surface and by the high frequency altemations of wet and dry environmental conditions around the samples.
基金supported by the National Science Foundation of China(No.41576076)the National Environmental Corrosion Platform(NECP)the National Key Basic Research Program(‘‘973 Program,’’No.2014CB643300)
文摘Experiments were designed to simulate the corrosion of a low-carbon steel exposed to a marine splash zone. The composition and morphology of the rust were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive spectrometry and scanning electron microscopy. Corrosion resistance of the rust films was demonstrated by the electrochemical impedance spectroscopy. The wettability of the steel surface was calculated from the data conceruing the wetting degree and the conductivity. The results showed that, in the initial stage, the products of the outer rust layer were mainly made up of Fe（Ⅲ） oxyhydroxide, while the main component of the inner rust layer was magnetite. With an increase in the corrosion time, the inner rust layer continuously turned into the outer rust layer. In addition, both rust layers became dense, thus playing a protective role with respect to matrix. The existence of the rust layer significantly prolonged the residence time of the seawater on the sample surface, a result that tends to improve the cathodic protection effect for steel structures exposed to marine splash zones.
