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Numerical investigations on effects of bluff body in flat plate micro thermo photovoltaic combustor with sudden expansion 被引量:1
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作者 鄂加强 黄海蛟 赵晓欢 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第4期975-982,共8页
In order to reveal combustion characteristics of H_2/air mixture in a micro-combustor with and without bluff body, the effects of inlet velocities, equivalence ratios and bluff body's blockage ratios on the temper... In order to reveal combustion characteristics of H_2/air mixture in a micro-combustor with and without bluff body, the effects of inlet velocities, equivalence ratios and bluff body's blockage ratios on the temperature field, pressure of the combustor wall, combustion efficiency and blow-off limit were investigated. The numerical results indicate that the sudden expansion plate micro combustor with bluff body could enhance the turbulent disturbance of the mixed gas in the combustion chamber and the combustion condition is improved. Moreover, a low-speed and high temperature recirculation region was formed between the sudden expansion step and the bluff body so that the high and uniform wall temperature(>1000 K) could be gotten. As a result, it could strengthen the mixing process, prolong the residence time of gas, control the flame position effectively and widen the operation range by the synergistic effect of the bluff body and steps. When the blockage ratio ranged from 0.3 to 0.6, it could be found that the bluff body could play a stabilizing effect and expand combustion blow burning limit, and combustion efficiency firstly was increased with the inlet velocity and equivalence ratio, and then was decreased. 展开更多
关键词 micro combustor bluff body sudden expansion numerical investigations
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Non-Newtonian Two-Phase Flow Characteristics across Sudden Expansion in Horizontal Rectangular Minichannel 被引量:1
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作者 Agus Santoso Daiki Goto +3 位作者 Tomoaki Takehira Ahmad Aslam Akimaro Kawahara Michio Sadatomi 《World Journal of Mechanics》 2016年第8期257-272,共17页
In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working l... In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working liquid, and air as the working gas. Liquid single-phase and air-liquid two-phase flow experiments were conducted at room temperature using the horizontal rectangular mini-channel with a sudden expansion. The cross-sectional dimensions of the narrow channel upstream from the sudden expansion were 2.79 mm, 3.09 mm and 2.94 mm in the height (H), the width (W) and the hydraulic diameter (DH), while those for the wide channel were 2.95 mm, 5.98 mm and 3.95 mm. The pressure distributions in the channels upstream and downstream from the expansion were measured with calibrated pressure transducer to determine the pressure change due to the expansion. The flow pattern, the bubble velocity, the bubble length, and the void fraction were measured with a high-speed video camera. The flow pattern map is drawn from the observed flow pattern, i.e., bubble flow, slug flow and annular flow in both the wide and the narrow channels. The bubble length data were compared with the calculation by the scaling law proposed by Kanezaki et al. and Kawahara et al. The pressure change data at the expansion were compared with our previous data together with several correlations in literature. Results of such experiment and comparisons are reported in the present paper. 展开更多
关键词 Non-Newtonian Two-Phase Flow sudden expansion MINICHANNEL
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FINITE ELEMENT ANALYSIS OF TRASINENT TWO DIMENSIONAL CHANNEL FLOW WITH A SUDDEN EXPANSION 被引量:3
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作者 Gao Dianrong Zhao Yongkai Wang Yiqun (Yanshan University) 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 1999年第4期270-275,共6页
The finite element method is employed to simulate incompressible viscous unsteady flow in two dimensional channel with a sudden expansion. The streamline patterns and the velocity vector plots are presented at differ... The finite element method is employed to simulate incompressible viscous unsteady flow in two dimensional channel with a sudden expansion. The streamline patterns and the velocity vector plots are presented at different expansion ratios and at different moment. The results obtained have certain significance to analyze the formation of eddies and energy loss in a sudden expansion channel flow and other complex channel flow. 展开更多
关键词 sudden expansion channel Finite element method STREAMLINE VELOCITY Energy loss
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Pressure Characteristics Study for the Configuration of Sudden Expansion with Central Restriction and Suction
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作者 Tridibesh Das Somnath Chakrabarti 《Open Journal of Fluid Dynamics》 2016年第1期30-41,共12页
In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are consi... In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are considered from 50 to 200, suction (S) from 2% to 10% of inlet mass flow, percentage of central restriction (CR) from 0% to 40% and aspect ratio (AR) from 2 to 6. The effects of each variable on average static pressure distribution and average stagnation pressure distribution have been studied in detail. The results have been compared with the configuration of plain sudden expansion, and sudden expansion with central restriction only. From the study, it is noted that maximum magnitude of average static pressure rise from throat increases with the increase in percentage of suction, flow Reynolds number and percentage of central restriction. This magnitude is higher at lower aspect ratio. Also, it is observed that maximum magnitude of average static pressure rise from throat is always more in case of suction configuration compared to the case of configuration of without suction. Average stagnation pressure drop at any section increases with the increase in percentage of suction and percentage of central restriction, but it decreases with the increase in Reynolds number. It is noted that higher pressure drop at any section occurs at higher aspect ratio. This pressure drop at a section is more in case of suction configuration compared to the case of without suction. 展开更多
关键词 sudden expansion Central Restriction Reynolds Number SUCTION
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Adsorption of phosphorus in sediment re-suspension under sudden expansion flow conditions 被引量:3
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作者 LIANG Wen WANG Ze +1 位作者 JIAO Zeng-xiang WAN Jun 《Journal of Hydrodynamics》 SCIE EI CSCD 2013年第1期112-117,共6页
Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstr... Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstream and the recirculation regions to analyze the basic features of this flow field. The adsorption of the phosphorus in the sediment is studied by adding the bacteriostatic agent. The results show that the flow speed in the mainstream region is higher than that in the recirculation region. However, the turbulence intensity in the recirculation region increases more than that in the mainstream region. The adsorption of the phosphorus in the sediment includes the physisorption and the biosorption, and the former is stronger than the latter. With the biosorption in the phosphorus removal process, the phosphorus released by the sediment is mainly completed by the poly-P bacteria in the anaerobic condition. The adsorption of the phosphorus in the sediment in the mainstream region of a sudden expansion water flow is strong and stable, whereas the adsorption in the sediment in the recirculation region is largely fluctuated. 展开更多
关键词 sudden expansion flow SEDIMENT PHOSPHORUS adsorption effect
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EXPERIMENTAL INVESTIGATION OF CAVITATION IN A SUDDEN EXPANSION PIPE 被引量:3
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作者 ZHANG Jian-min YANG Qing WANG Yu-rong XU Wei-lin CHEN Jian-gang 《Journal of Hydrodynamics》 SCIE EI CSCD 2011年第3期348-352,共5页
For sudden expansion pipes, experiments were carried 'Out to study the cavitation inception for various enlargement ratios in high speed flows. The flow velocity of the prototype reaches 50 m/s in laboratory. The rel... For sudden expansion pipes, experiments were carried 'Out to study the cavitation inception for various enlargement ratios in high speed flows. The flow velocity of the prototype reaches 50 m/s in laboratory. The relationship between the expansion ratio and the incipient cavitation number is obtained. The scale and velocity effects are revealed. It is shown that Keller's revised formula should be modified to calculate the incipient cavitation number when the forecasted velocity of the flows in the prototype exceeds the experimental velocity. 展开更多
关键词 high speed flows sudden expansion pipe cavitation incipient scale effect
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Pressure recovery characteristics for a dilute gas-particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach 被引量:2
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作者 Santosh Kumar Senapati Sukanta Kumar Dash 《Particuology》 SCIE EI CAS CSCD 2020年第3期100-111,共12页
This work applies the Eulerian-Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas-particle suspensio... This work applies the Eulerian-Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas-particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid loading.To do so,the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion;a satisfactory agreement was obtained.Initially,the effect of the two significant numerical parameters namely,the speculairty coefficient and the coefficient of restitution for particle-particle collisions were investigated and then,for fixed combinations of these parameters the effect of particle-phase volume fraction,particle density,particle size,and inlet slip ratio were studied.It was concluded that pressure recovery diminishes as the speculairty coefficient increases and the particle-particle coefficient of restitution decreases.Pressure recovery was found to increase with increasing solid volume fraction for coarse particles whereas,for fine particles,a critical volume fraction is obtained above which pressure recovery reduces.An increase in slip ratio is found to diminish pressure recovery.Similarly,at relatively higher solid volume fractions,a critical diameter was found,above and below which pressure recovery decreases. 展开更多
关键词 Gas-solid flow sudden expansion pipe Eulerian-Eulerian model Pressure recovery Vertically downward flow
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Measurement and simulation of the two-phase velocity correlation in sudden-expansion gas-particle flows 被引量:3
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作者 Li-Xing Zhou.Yang Liu.Yi Xu Department of Engineering Mechanics,Tsinghua University,100084 Beijing,China Marine Engineering College,Dalian Maritime University,116026 Dalian,China 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2011年第4期494-501,共8页
In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer (PDPA) and simulated the system behavior by ... In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer (PDPA) and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes (RANS) model and a large-eddy simulation (LES). The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups (30μm, 50μm, and 95μm) and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model. 展开更多
关键词 PDPA measurement - Simulation Two-phasevelocity correlation sudden expansion gas-particle flows
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Platelet adhesion to the surface of a sudden tubular expansion tube under swirling flow condition
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作者 Fan ZHAN,Xiaoyan DENG,Yubo FAN(School of Biological Science&Medical Engineering,Beihang University,Beijing,100191,China) 《医用生物力学》 EI CAS CSCD 2009年第S1期22-22,共1页
The size mismatch in an end-to-end vascular anastomosis between the host vessel and the graft may cause flow disturbance and predispose to thrombosis [1].Although a number of techniques have been employed to reduce th... The size mismatch in an end-to-end vascular anastomosis between the host vessel and the graft may cause flow disturbance and predispose to thrombosis [1].Although a number of techniques have been employed to reduce the risk of anastomotic thrombosis due to the size mismatch。 展开更多
关键词 flow Platelet adhesion to the surface of a sudden tubular expansion tube under swirling flow condition
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Oxygen transfer characteristics of water and bubble mixture pipe flow through two sudden contractions and expansions 被引量:1
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作者 尹则高 解绍华 +1 位作者 程东升 龙翔宇 《Journal of Hydrodynamics》 SCIE EI CSCD 2014年第5期745-750,共6页
The dissolved oxygen (DO) concentration is an important index of water quality. This paper studies the dissolved oxygen recovery of the water and bubble mixture pipe flow through two sudden contractions and expansio... The dissolved oxygen (DO) concentration is an important index of water quality. This paper studies the dissolved oxygen recovery of the water and bubble mixture pipe flow through two sudden contractions and expansions. A 3-D computational fluid dy- namics model is established to simulate the water and bubble mixture flow with a DO transport model. An experiment is conducted to validate the mathematical model. The mathematical model is used to evaluate the effect of geometric parameters on the head loss coefficient, the relative saturation coefficient and the oxygen absorption efficiency. It is found that the contraction ratio is a signi- ficant influencing factor, other than the relative length and the relative distance. Given the same relative length and relative distance, the head loss coefficient, the relative saturation coefficient and the oxygen absorption efficiency increase with the decrease of the contraction ratio, respectively. Given the same relative length and contraction ratio, the head loss coefficient increases with the in- crease of the relative distance firstly, and then decreases gradually, in contrast, the relative saturation coefficient and the oxygen ab- sorption efficiency decrease with the increase of the relative distance firstly, and then increase gradually, the relative saturation coefficient and the oxygen absorption efficiency are inversely proportional to the head loss coefficient, respectively. 展开更多
关键词 dissolved oxygen two sudden contractions and expansions head loss coefficient relative saturation coefficient oxygen absorption efficiency
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Experimental investigation of tubing collar's influence on hydrodynamic behavior of annular duct flow
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作者 Yi-Su Zhou Zhong-Wei Huang +3 位作者 Zhuang-Zhuang Zhang Tian-Wen Jiang Rui-Yue Yang Ming-He Zhang 《Petroleum Science》 SCIE CAS CSCD 2022年第5期2326-2342,共17页
Tubing collars’influence on hydrodynamic behavior of annular duct flow has been investigated using Particle Image Velocity(PIV)technology.PIV has become an efficient method for complex transient flows visualization.A... Tubing collars’influence on hydrodynamic behavior of annular duct flow has been investigated using Particle Image Velocity(PIV)technology.PIV has become an efficient method for complex transient flows visualization.A water flow loop with two replaceable variable cross-sections(VCS),75-90 mm and 90-110 mm,in a 129 mm inner diameter(ID)pipe was used.The whole field of the variable cross-section annulus(VCSA)was visualized,including forward-facing step(FFS),narrow annulus(NA),and backwardfacing step(BFS)flow.The VCSA ratio and Reynolds(Re)number influence on streamline distribution,velocity distribution,and turbulence intensity were discussed.Results showed that the recirculation is easier to form in BFS than FFS flow under the same condition.The VCSA ratio affects the formation of recirculation zones and the location of the reattachment point.Reynolds number mainly affects BFS flow by influencing the main velocity component-axial velocity.The turbulence intensity is relatively high in BFS than FFS flow and is larger at y/h>1.0 than y/h<1.0.Furthermore,the streamwise cohere nt structures reveal that the first two modes are predominant and represent the main characteristics of the flow by proper orthogonal decomposition(POD)method. 展开更多
关键词 Variable cross-section annulus flow sudden contraction and expansion Hydrodynamic behavior PIV POD
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