Based on the observation of a model test and in combination with some theoretical analysis, the researches of some basic hydrodynamics characteristics of cavity spiral flow in a large size level pipe with a shaft-inle...Based on the observation of a model test and in combination with some theoretical analysis, the researches of some basic hydrodynamics characteristics of cavity spiral flow in a large size level pipe with a shaft-inlet is presented in the paper, which include the basic flow pattern, formation condition of the cavity spiral flow, discharge Q, cavity diameter d0, wall pressure coefficient Cpw, velocity distribution, total energy dissipation rate η etc. The results show that the basic flow patterns can be divided into three zones according to the variations in amount of ventilation Ф, cavity diameter d0 and gas pressure p0 within cavity spiral flow when the upstream and downstream water level changes and that the basic hydrodynamics characteristics change with the flow pattern and have the different behaviour.展开更多
In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different para...In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.展开更多
Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat ...Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.展开更多
Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization...Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.展开更多
Chimera states are firstly discovered in nonlocally coupled oscillator systems.Such a nonlocal coupling arises typically as oscillators are coupled via an external environment whose characteristic time scaleτis so sm...Chimera states are firstly discovered in nonlocally coupled oscillator systems.Such a nonlocal coupling arises typically as oscillators are coupled via an external environment whose characteristic time scaleτis so small(i.e.,τ→0)that it could be eliminated adiabatically.Nevertheless,whether the chimera states still exist in the opposite situation(i.e.,τ≫1)is unknown.Here,by coupling large populations of Stuart–Landau oscillators to a diffusive environment,we demonstrate that spiral wave chimeras do exist in this oscillator-environment coupling system even whenτis very large.Various transitions such as from spiral wave chimeras to spiral waves or unstable spiral wave chimeras as functions of the system parameters are explored.A physical picture for explaining the formation of spiral wave chimeras is also provided.The existence of spiral wave chimeras is further confirmed in ensembles of FitzHugh–Nagumo oscillators with the similar oscillator-environment coupling mechanism.Our results provide an affirmative answer to the observation of spiral wave chimeras in populations of oscillators mediated via a slowly changing environment and give important hints to generate chimera patterns in both laboratory and realistic chemical or biological systems.展开更多
The formations of desiccation cracks and their pattems in drying droplets of protein solutions are studied experimentally. The solvent evaporation causes the dehydration self-organization phenomenon in colloidal dropl...The formations of desiccation cracks and their pattems in drying droplets of protein solutions are studied experimentally. The solvent evaporation causes the dehydration self-organization phenomenon in colloidal droplets, followed by the formations of desiccation cracks. Two categories of highly ordered crack patterns, which we name ＂daisy＂ and ＂wavy-ring＂, are identified in the drying droplets. We explore the shifting of crack patterns from the ＂daisy＂ to the ＂wavy-ring＂ by varying the concentration of protein droplets. The results show that the concentration correlates with the pattern of deposition film directly, and modulates the periodicity of the crack pattern. We investigate the formations and periodicities of these two kinds of crack patterns, and obtain the scaling law of periodicity of the ＂wavy-ring＂ crack pattern. The relationship between the deposition pattern and the highly ordered crack patterns is also examined. This study will help in understanding the formation mechanisms of crack patterns in drying droplets of protein solutions and assist the future design of crack patterns in practical applications.展开更多
文摘Based on the observation of a model test and in combination with some theoretical analysis, the researches of some basic hydrodynamics characteristics of cavity spiral flow in a large size level pipe with a shaft-inlet is presented in the paper, which include the basic flow pattern, formation condition of the cavity spiral flow, discharge Q, cavity diameter d0, wall pressure coefficient Cpw, velocity distribution, total energy dissipation rate η etc. The results show that the basic flow patterns can be divided into three zones according to the variations in amount of ventilation Ф, cavity diameter d0 and gas pressure p0 within cavity spiral flow when the upstream and downstream water level changes and that the basic hydrodynamics characteristics change with the flow pattern and have the different behaviour.
基金supported by the National Natural Science Foundation of China (Grant number 51776015)
文摘In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.
基金supported by the National Natural Science Foundation of China(52304067,62273213)the Natural Science Foundation of Shandong Province of China(ZR2021QE073)+1 种基金the Natural Science Foundation of Shandong Province for Innovation and Development Joint Funds(ZR2022LZH001)the China Postdoctoral Science Foundation(2023M732111)。
文摘Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.
基金supported in part by National Key R&D Program of China(Grant No.2018YFB1304600)CAS Interdisciplinary Innovation Team(Grant No.JCTD-2018-11)the Natural Science Foundation of China(Grant No.51775541).
文摘Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.
基金the National Natural Science Foundation of China under Grant No.11875120the Natural Science Foundation of Zhejiang Province under Grant No.LY16A050003.
文摘Chimera states are firstly discovered in nonlocally coupled oscillator systems.Such a nonlocal coupling arises typically as oscillators are coupled via an external environment whose characteristic time scaleτis so small(i.e.,τ→0)that it could be eliminated adiabatically.Nevertheless,whether the chimera states still exist in the opposite situation(i.e.,τ≫1)is unknown.Here,by coupling large populations of Stuart–Landau oscillators to a diffusive environment,we demonstrate that spiral wave chimeras do exist in this oscillator-environment coupling system even whenτis very large.Various transitions such as from spiral wave chimeras to spiral waves or unstable spiral wave chimeras as functions of the system parameters are explored.A physical picture for explaining the formation of spiral wave chimeras is also provided.The existence of spiral wave chimeras is further confirmed in ensembles of FitzHugh–Nagumo oscillators with the similar oscillator-environment coupling mechanism.Our results provide an affirmative answer to the observation of spiral wave chimeras in populations of oscillators mediated via a slowly changing environment and give important hints to generate chimera patterns in both laboratory and realistic chemical or biological systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1562105,11372313)the Chinese Academy of Sciences through CAS Interdisciplinary Innovation Team Project+1 种基金the Chinese Academy of Sciences Key Research Program of Frontier Sciences(Grant No.QYZDJ-SSW-JSC019)the Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDB22040401)
文摘The formations of desiccation cracks and their pattems in drying droplets of protein solutions are studied experimentally. The solvent evaporation causes the dehydration self-organization phenomenon in colloidal droplets, followed by the formations of desiccation cracks. Two categories of highly ordered crack patterns, which we name ＂daisy＂ and ＂wavy-ring＂, are identified in the drying droplets. We explore the shifting of crack patterns from the ＂daisy＂ to the ＂wavy-ring＂ by varying the concentration of protein droplets. The results show that the concentration correlates with the pattern of deposition film directly, and modulates the periodicity of the crack pattern. We investigate the formations and periodicities of these two kinds of crack patterns, and obtain the scaling law of periodicity of the ＂wavy-ring＂ crack pattern. The relationship between the deposition pattern and the highly ordered crack patterns is also examined. This study will help in understanding the formation mechanisms of crack patterns in drying droplets of protein solutions and assist the future design of crack patterns in practical applications.
