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Flow instability criteria in processing map of superalloy GH79 被引量:4
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作者 周舸 丁桦 +2 位作者 曹富荣 韩寅奔 张北江 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第7期1575-1581,共7页
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GE... Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79. 展开更多
关键词 nickel-based superalloy hot compression flow instability criterion processing map
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FURTHER OBSERVATIONS OF LATE TRANSITION PROCESSES IN CROSSFLOW INSTABILITY EXPERIMENT
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作者 吴永健 明晓 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2000年第1期26-30,共5页
The experiments of primary and secondary instabilities with controlled excitation are carried out on a swept flat plate to study the process leading to the final breakdown of laminar flow. Two types of high frequency ... The experiments of primary and secondary instabilities with controlled excitation are carried out on a swept flat plate to study the process leading to the final breakdown of laminar flow. Two types of high frequency secondary instabilities are identified. The most amplified mode is centered about the inflection point of the crosswise profile of the boundary layer and is interpreted as inflectional instability, the other occurs in the one third of the boundary layer from the wall. The high frequency disturbances are highly amplified but they also saturate similarly to the primary and nonlinearly generated disturbances. Their main effect in the final breakdown seems interact with the disturbances is developed and thus widens the frequency spectrum to turbulent state. 展开更多
关键词 three dimensional boundary layer cross flow instability secondary instability final onset of transition BREAKDOWN
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Startup scheme optimization and flow instability of natural circulation lead-cooled fast reactor SNCLFR-100 被引量:4
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作者 Wen-Shun Duan Ze-Ren Zou +1 位作者 Xiao Luo Hong-Li Chen 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2021年第11期191-200,共10页
Owing to the inherent instability of the natural circulation system,flow instability can easily occur during the operation of a natural circulation lead-cooled fast reactor,especially during the startup phase.A compre... Owing to the inherent instability of the natural circulation system,flow instability can easily occur during the operation of a natural circulation lead-cooled fast reactor,especially during the startup phase.A comprehensive startup scheme for SNCLFR-100,including primary and secondary circuits,is proposed in this paper.It references existing more mature startup schemes in various reactor types.It additionally considers the restriction conditions on the power increase in other schemes and the characteristics of lead-based coolant.On this basis,the multi-scale coupling code ATHLET-OpenFOAM was used to study the flow instability in the startup phase under different power-step amplitudes and power duration times.The results showed that obvious flow instability phenomena were found in the different startup schemes,such as the short-term backflow phenomenon of the core at the initial time of the startup.Moreover,an obvious increase in the flow rate and temperature to the peak value at the later stage of a continuous power rise was observed,as well as continuous oscillations before reaching a steady state.It was determined that the scheme with smaller power-step amplitude and a longer power duration time requires more time to start the reactor.Nevertheless,it will be more conducive to the safe and stable startup of the reactor. 展开更多
关键词 Natural circulation Lead-cooled fast reactor Startup scheme flow instability Multi-scale coupling
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Cold Flow Experiments and Acoustic Investigation on Pressure Oscillation Induced by Flow Instability
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作者 陈晓龙 何国强 刘佩进 《Defence Technology(防务技术)》 SCIE EI CAS 2010年第2期85-90,共6页
Pressure oscillation in solid rocket motor is believed to be the results of the interaction between the flow instability and the acoustics of combustion chamber.Several reasonable and necessary hypothesizes are given ... Pressure oscillation in solid rocket motor is believed to be the results of the interaction between the flow instability and the acoustics of combustion chamber.Several reasonable and necessary hypothesizes are given to establish an equation to describe this coupling.A cold flow motor called CVS60D(corner vortex shedding 60°)was designed to study the flow-acoustic coupling based on theoretical analysis.Experimental investigations were carried out to determine the acoustics of CVS60D.Corner vortex shedding is generated at the backward facing step which is designed similar to the geometry of the motor with finocyl propellant after the burnout of its fins.A pintle was used to modify the velocity in the duct to change the frequency of vortex shedding.It is found that large amplitude pressure oscillation occurs when the pintle moves to a range of specific position,which indicates that the frequency of vortex shedding is close to one order of acoustic modes of combustion chamber.The amplitude of pressure oscillation changes as the pintle moves. 展开更多
关键词 propulsion system of aviation & aerospace cold flow experiment ACOUSTICS pressure oscillation flow instability
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Flow instability of supercritical hydrocarbon fuel in a multi-channel cooling system
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作者 Yichao JIN Kun WU Xuejun FAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第2期283-295,共13页
Thermally-induced flow instabilities are a critical issue in multi-channel regenerative cooling systems.In particular,the interactions between Density-Wave Oscillations(DWO)and Flow Maldistribution(FMD)can result in c... Thermally-induced flow instabilities are a critical issue in multi-channel regenerative cooling systems.In particular,the interactions between Density-Wave Oscillations(DWO)and Flow Maldistribution(FMD)can result in complex and disastrous instability phenomena.This study investigates the instability behaviors of hydrocarbon fluid in a four-channel system with a constant heat flux ratio using both frequency-and time-domain methods.As the heat flux increases,the in-tube flow sequentially destabilizes in each channel and converges to new equilibrium states,leading to the emergence of FMD phenomena.This also causes the system eigenvalue to change repeatedly from negative to positive rather than increasing monotonically.Additionally,the system eigenvalues are between those of the two most unstable channels,indicating that the stability behavior of the entire system is dictated by the most unstable channel.After FMD occurs,flow oscillations are activated in channels with weak stability,and the in-tube flow is observed to evolve into various flow patterns,including stable flow,self-sustained oscillation,oscillation divergence,quasiperiodic oscillation,and oscillation excursion.The novel instability mode of oscillation excursion involves a spontaneous transition of operating states.It oscillates from an equilibrium state and then stabilizes at a new operational state after oscillation-induced redistribution.However,the newfound stable state may also be only temporary,with the in-tube flow regressing to the initial state,resulting in quasi-periodic oscillation. 展开更多
关键词 COOLING Supercritical fluids Hydrocarbons flow instability flow maldistribution Density-wave oscillations
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Identification of Backflow Vortex Instability in Rocket Engine Inducers
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作者 Luca d’Agostino 《风机技术》 2024年第5期7-18,共12页
Bayesian estimation is applied to the analysis of backflow vortex instabilities in typical three-and four bladed liquid propellant rocket(LPR)engine inducers.The flow in the impeller eye is modeled as a set of equally... Bayesian estimation is applied to the analysis of backflow vortex instabilities in typical three-and four bladed liquid propellant rocket(LPR)engine inducers.The flow in the impeller eye is modeled as a set of equally intense and evenly spaced 2D axial vortices,located at the same radial distance from the axis and rotating at a fraction of the impeller speed.The circle theorem and the Bernoulli’s equation are used to predict the flow pressure in terms of the vortex number,intensity,rotational speed,and radial position.The theoretical spectra so obtained are frequency broadened to mimic the dispersion of the experimental data and parametrically fitted to the measured pressure spectra by maximum likelihood estimation with equal and independent Gaussian errors.The method is applied to three inducers,tested in water at room temperature and different loads and cavitation conditions.It successfully characterizes backflow instabilities using the signals of a single pressure transducer flush-mounted on the casing of the impeller eye,effectively by-passing the aliasing and data acquisition/reduction complexities of traditional multiple-sensor cross correlation methods.The identification returns the estimates of the model parameters and their standard errors,providing the information necessary for assessing the accuracy and statistical significance of the results.The flowrate is found to be the major factor affecting the backflow vortex instability,which,on the other hand,is rather insensitive to the occurrence of cavitation.The results are consistent with the data reported in the literature,as well as with those generated by the auxiliary models specifically developed for initializing the maximum likelihood searches and supporting the identification procedure. 展开更多
关键词 Aerospace Propulsion Liquid Propellant Rockets LPR Feed Turbopumps Turbopump flow Instabilities BackflowVortex instability Bayesian Parametric Identification
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Flow Instability of a Centrifugal Pump Determined Using the Energy Gradient Method 被引量:5
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作者 Li Yi Dong Wenlong +2 位作者 He Zhaohui Huang Yuanmin Jiang Xiaojun 《Journal of Thermal Science》 SCIE EI CAS CSCD 2015年第1期44-48,共5页
The stability of the centrifugal pump has not been well revealed because of the complexity of internal flow. To analyze the flow characteristics of a centrifugal pump operating at low capacity, methods of numerical si... The stability of the centrifugal pump has not been well revealed because of the complexity of internal flow. To analyze the flow characteristics of a centrifugal pump operating at low capacity, methods of numerical simulation and experimental research were adopted in this paper. Characteristics of the inner flow were obtained. Standard k-s turbulence models were used to calculate the inner flow of the pump under off-design conditions. The distri- bution of the energy gradient function K was obtained by three-dimensional numerical simulation at different flow rates. The relative velocity component was acquired from the absolute velocity obtained in particle image velocimetry. By comparing with experimental results, it was found that flow instability occurs at the position of maximum K. The flow stability reduces with an increasing flow rate. The research results provide a theoretical basis for the optimization design of a centrifugal pump. 展开更多
关键词 centrifugal pump flow instability three-dimensional particle image velocimetry numerical simula-tion energy gradient
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A Comparative Study of Various Flow Instability Criteria in Processing Map of Superalloy GH4742 被引量:4
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作者 Ge Zhou Hua Ding +1 位作者 Furong Cao Beijiang Zhang 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2014年第3期217-222,共6页
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasa... Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasad, Gegel, Malas, Murty and Semiatin were compared, and the physical significance of parameters was analyzed. Meanwhile, the processing maps with different instability criteria were obtained. It was shown that instability did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020- 1130℃, corresponding to the strain rate range of 5 × 10-4-3.2 × 10-3 s-1. The domain is appropriate for the processing deformation of superalloy GH4742. 展开更多
关键词 GH4742 superalloy Hot compression tests flow instability criterion Processing map
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Effects of the radial blade loading distribution and B parameter on the type of flow instability in a low-speed axial compressor 被引量:2
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作者 Qiushi LI Simin LI Tianyu PAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第7期1470-1479,共10页
Previous studies showed that an axisymmetric hub-initiated disturbance defined as partial surge may initiate the stall of a transonic compressor; to reveal the instability evolution under full-span incompressible flow... Previous studies showed that an axisymmetric hub-initiated disturbance defined as partial surge may initiate the stall of a transonic compressor; to reveal the instability evolution under full-span incompressible flow for different levels of hub loading and B parameter, an experimental investigation is conducted on a single-stage low-speed compressor. Experimental results show that under a uniform inflow condition without inlet flow distortion, a modal-type stall inception dominates in this low-speed compressor. When an inlet screen introducing hub distortion is used to increase the hub loading, a compressor stall is initiated by a modal wave, but large disturbances are present in the hub region before the compressor stall, which become stronger as the hub loading increases. Under high hub loading and large B parameter(implemented by adding hub distortion through an inlet screen and enlarging the outlet plenum volume, respectively), a compressor stall is triggered by an axisymmetric hub-initiated disturbance, which is much different from the modal-like disturbances. The beginning of this axisymmetric disturbance may be captured over 800 rotor revolutions prior to the onset of stall, and the amplitude grows with time. The disturbance is hub-initiated because the disturbance signal at the hub is detected much earlier than that at the tip; meanwhile, the frequency of this axisymmetric disturbance changes with the length of the inlet duct. The characteristics of instability evolution in the low-speed compressor are also compared with those in a transonic compressor. 展开更多
关键词 Axisymmetric disturbance B parameter flow instability Low-speed axial compressor Radial blade loading distribution
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Numerical Analysis of Flow Instability in the Water Wall of a Supercritical CFB Boiler with Annular Furnace 被引量:5
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作者 XIE Beibei YANG Dong +2 位作者 XIE Haiyan NIE Xin LIU Wanyu 《Journal of Thermal Science》 SCIE EI CAS CSCD 2016年第4期372-379,共8页
In order to expand the study on flow instability of supercritical circulating fluidized bed(CFB) boiler,a new numerical computational model considering the heat storage of the tube wall metal was presented in this pap... In order to expand the study on flow instability of supercritical circulating fluidized bed(CFB) boiler,a new numerical computational model considering the heat storage of the tube wall metal was presented in this paper.The lumped parameter method was proposed for wall temperature calculation and the single channel model was adopted for the analysis of flow instability.Based on the time-domain method,a new numerical computational program suitable for the analysis of flow instability in the water wall of supercritical CFB boiler with annular furnace was established.To verify the code,calculation results were respectively compared with data of commercial software.According to the comparisons,the new code was proved to be reasonable and accurate for practical engineering application in analysis of flow instability.Based on the new program,the flow instability of supercritical CFB boiler with annular furnace was simulated by time-domain method.When 1.2 times heat load disturbance was applied on the loop,results showed that the inlet flow rate,outlet flow rate and wall temperature fluctuated with time eventually remained at constant values,suggesting that the hydrodynamic flow was stable.The results also showed that in the case of considering the heat storage,the flow in the water wall is easier to return to stable state than without considering heat storage. 展开更多
关键词 supercritical CFB with annular furnace heat storage flow instability wall temperature numerical analysis
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Effect of bent inlet pipe on the flow instability behavior of centrifugal compressors 被引量:1
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作者 Zhenzhong SUN Baotong WANG +3 位作者 Xinqian ZHENG Tomoki KAWAKUBO Hideaki TAMAKI Ryuusuke NUMAKURA 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第8期2099-2109,共11页
Bent inlet pipes are often used in centrifugal compressors due to limited installation space,and an understanding of the effect on compressor stability is essential for safety and durability.This paper firstly investi... Bent inlet pipes are often used in centrifugal compressors due to limited installation space,and an understanding of the effect on compressor stability is essential for safety and durability.This paper firstly investigates flow instability behaviors in two compressors,one with a straight inlet pipe and the other with an S-shaped bent pipe.In detail,it analyzes the resulting flow fields,instability evolution paths and surge boundaries.The results show that the S-shaped pipe obviously affects the flow field at high mass flow rates,while reverse flow mainly influences the flow field at low mass flow rates.Reverse flow first occurs at certain flow passages with a high pressure difference that is predominantly decided by the volute rather than the S-shaped bent pipe.In addition,centrifugal compressors can tolerate reverse flow to some extent so that surge would not occur immediately if reverse flow occurs unless the reverse flow region extends circumferentially and radially to a sufficiently large size.Since the S-shaped pipe is not dominant in the creation and extension of reverse flow,it does not exacerbate the stability of the central compressor to a great extent.Last but not least,the S-shaped pipe is noted to delay the occurrence of surge at 90%rotating speed,which suggests the possibility of improving compressor stability with bent inlet pipes.This result differs from the conventional understanding that inlet distortion usually deteriorates compressor stability and emphasizes the particularity of centrifugal compressors. 展开更多
关键词 Bent pipe Centrifugal compressor flow field flow instability Surge boundary
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Electromagnetic control of the instability in the liquid metal flow over a backward-facing step
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作者 Ya-Dong Huang Jia-Wei Fu Long-Miao Chen 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第12期306-314,共9页
The tile-type electromagnetic actuator(TEA)and stripe-type electromagnetic actuator(SEA)are applied to the active control of the perturbation energy in the liquid metal flow over a backward-facing step(BFS).Three cont... The tile-type electromagnetic actuator(TEA)and stripe-type electromagnetic actuator(SEA)are applied to the active control of the perturbation energy in the liquid metal flow over a backward-facing step(BFS).Three control strategies consisting of base flow control(BFC),linear model control(LMC)and combined model control(CMC)are considered to change the amplification rate of the perturbation energy.CMC is the combination of BFC and LMC.SEA is utilized in BFC to produce the streamwise Lorentz force thus adjusting the amplification rate via modifying the flow structures,and the magnitude of the maximum amplification rate could reach to 6 orders.TEA is used in LMC to reduce the magnitude of the amplification rate via the wall-normalwise Lorentz force,and the magnitude could be decreased by 2 orders.Both TEA and SEA are employed in CMC where the magnitude of the amplification rate could be diminished by 3 orders.In other words,the control strategy of CMC could capably alter the flow instability of the liquid metal flow. 展开更多
关键词 electromagnetic actuator backward-facing step flow flow instability flow control
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INSTABILITY OF HAGEN-POISEUILLE FLOW FOR NON-AXISYMMETRIC MODE
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作者 王发民 J. T. Stuart (F. R. S.) 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第5期407-417,共11页
An investigation is described for instability problem of flow through a pipe of circular cross section. As a disturbance motion, we consider a general non-axisym-metric mode. An associated amplitude or modulation equa... An investigation is described for instability problem of flow through a pipe of circular cross section. As a disturbance motion, we consider a general non-axisym-metric mode. An associated amplitude or modulation equation has been derived for this disturbance motion. This equation belongs to a diffusion type.The coefficient of it can be negative while Reynolds number increases, because of the complex interaction between molecular diffusion and convection. The negative diffusivity, when it occurs, causes a concentration and focussing of energy within decaying slugs, acting as a role of reversing natural decays. 展开更多
关键词 instability OF HAGEN-POISEUILLE flow FOR NON-AXISYMMETRIC MODE
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Linear and Non-Linear Dynamics of Inertial Waves in a Rotating Cylinder with Antiparallel Inclined Ends 被引量:1
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作者 Mariya Shiryaeva Mariya Subbotina Stanislav Subbotin 《Fluid Dynamics & Materials Processing》 EI 2024年第4期787-802,共16页
This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions ... This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions where the fluid depth increases or decreases with radius.Three different regimes are found:inertial wave attractor,global oscillations(the cavity’s resonant modes)and regime of symmetric reflection of wave beams.In linear wave regimes,a steady single vortex elongated along the rotation axis is generated.The location of the wave’s interaction with the sloping ends determines the vortex position and the vorticity sign.In non-linear regimes several pairs of the triadic resonance subharmonics are detected simultaneously.The instability of triadic resonance is accompanied by the periodic generation of mean vortices drifting in the azimuthal direction.Moreover,the appearance frequency of the vortices is consistent with the low-frequency subharmonic of the triadic resonance.The experimental results shed light on the mechanisms of the inertial wave interaction with zonal flow and may be useful for the development of new methods of mixing. 展开更多
关键词 ROTATION inertial wave attractor triadic resonance zonal flow instability
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Instability of cylinder wake under open-loop active control 被引量:1
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作者 Yadong HUANG Benmou ZHOU Zhaolie TANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2017年第3期439-452,共14页
Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic... Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface,adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re = 300 can be transformed from B to A with N = 1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926 D and 0.822 D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation.All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force. 展开更多
关键词 flow instability global stability analysis open-loop active control streamwise Lorentz force wake stabilization transition delay
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A Novel Asymmetric Check Microvalve for Suppressing Flow Boiling Instability in Microchannels
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作者 ZHOU Fan ZHAO Yang +2 位作者 YIN Ershuai HU Dinghua LI Qiang 《Journal of Thermal Science》 SCIE EI CAS CSCD 2024年第6期2336-2347,共12页
Flow boiling in microchannels has attracted wide attention due to its excellent heat transfer capability,but flow boiling instability is a huge challenge limiting its application.Instability can lead to a series of pr... Flow boiling in microchannels has attracted wide attention due to its excellent heat transfer capability,but flow boiling instability is a huge challenge limiting its application.Instability can lead to a series of problems,such as uneven flow distribution,temperature and pressure drop oscillations.This work proposes a novel asymmetric check microvalve(ACMV)structure,exhibiting high ratio of resistance between the reverse and forward flow.The results show the reverse pressure drop of the ACMV structure is 2.06 times that of the forward pressure drop,and the forward flow resistance of the ACMV structure is 16%smaller than that of the conventional inlet restrictor.In addition,bubble dynamics of an isolated bubble in the generated channel under dual outlet condition was numerically investigated.It is found that the bubble grows symmetrically in the rectangular channel upstream and downstream.The distance of bubble movement downstream in the microchannel with ACMV is three times that of the microchannel with inlet restrictor.The microchannel with ACMV can suppress the backflow of isolated bubble better than microchannel with inlet restrictor.Moreover,the growth of the bubble downstream extends the effective evaporation domain,which contributes to the enhanced bubble growth rate.The ACMV is expected to be a potential replacement for the conventional inlet restrictor,which provides a novel and efficient solution for future heat dissipation from high power devices. 展开更多
关键词 flow boiling instability topology optimization MICROCHANNEL bubble dynamics
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NUMERICAL STUDY OF BUOUNCY- AND THERMOCAPILLARY-DRIVEN FLOWS IN A CAVITY
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作者 陆夕云 庄礼贤 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1998年第2期130-138,共9页
Thermocapillary-and buoyancy-driven convection in open cavities with differentially heated endwalls is investigated by numerical solutions of the two- dimensional Navier-Stokes equations coupled with the energy equati... Thermocapillary-and buoyancy-driven convection in open cavities with differentially heated endwalls is investigated by numerical solutions of the two- dimensional Navier-Stokes equations coupled with the energy equation. We studied the thermocapillary and buoyancy convection in the cavities, filled with low-Prandtl- number fluids, with two aspect-ratios A=1 and 4, Grashof number up to 10~5 and Reynolds number |Re|≤10~4. Our results show that thermocapillary can have a quite significant effect on the stability of a primarily buoyancy-driven flow, as well as on the flow structures and dynamic behavior for both additive effect (i.e., positive Re) and opposing effect (i.e., negative Re). 展开更多
关键词 thermocapillary-driven flow buoyancy-driven flow crystal growth numerical simulation flow instability
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Spatio-temporal instability of two-layer liquid film at small Reynolds numbers
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作者 王志亮 林松飘 周哲玮 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2010年第1期1-12,共12页
The onset of instability with respect to the spatio-temporally growing disturbance in a viscosity-stratified two-layer liquid film flow is analyzed. The known results obtained from the temporal theory of instability s... The onset of instability with respect to the spatio-temporally growing disturbance in a viscosity-stratified two-layer liquid film flow is analyzed. The known results obtained from the temporal theory of instability show that the flow is unstable in the limit of zero Reynolds numbers. The present theory predicts the neutral stability in the same limit. The discrepancy is explained. Based on the mechanical energy equation, a new mechanism of instability is found. The new mechanism is associated with the convective nature of the disturbance that is not Galilei invariant. 展开更多
关键词 flow instability film coating energy budget low Reynolds number Galilei invariant
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Large Eddy Simulations of Flow Instabilities in a Stirred Tank Gen-erated by a Rushton Turbine 被引量:4
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作者 樊建华 王运东 费维扬 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2007年第2期200-208,共9页
The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation (LES). The sliding mesh method was used for the coupli... The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation (LES). The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the "Shengcao-21C" supercomputer using a computational fluid dynamics (CFD) code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry (PIV) measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform (FFT) and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena. 展开更多
关键词 stirred tank flow instabilities computational fluid dynamics large eddy simulation κ-ε model particle image velocimetry
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Linear stability of plane creeping Couette flow for Burgers fluid 被引量:1
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作者 Kai-Xin Hu Jie Peng Ke-Qin Zhu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2013年第1期12-23,共12页
It is well known that plane creeping Couette flow of UCM and Oldroy-B fluids are linearly stable. However, for Burges fluid, which includes UCM and Oldroyd-B fluids as special cases, unstable modes are detected in the... It is well known that plane creeping Couette flow of UCM and Oldroy-B fluids are linearly stable. However, for Burges fluid, which includes UCM and Oldroyd-B fluids as special cases, unstable modes are detected in the present work. The wave speed, critical parameters and perturbation mode are studied for neutral waves. Energy analysis shows that the sustaining of perturbation energy in Poiseuille flow and Couette flow is completely different. At low Reynolds number limit, analytical solutions are obtained for simpli- fied perturbation equations. The essential difference between Burgers fluid and Oldroyd-B fluid is revealed to be the fact that neutral mode exists only in the former. 展开更多
关键词 Linear stability theory Burgers fluid Creeping Couette flow - Elastic instability
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