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Numerical simulation of flow separation over a backward-facing step with high Reynolds number 预览
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作者 Fang-fang Wang Shi-qiang Wu Sen-lin Zhu 《水科学与水工程:英文版》 EI CAS CSCD 2019年第2期145-154,共10页
Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices.In this study,LES and κ-ε models were developed for a specific geometrical configuration of b... Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices.In this study,LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS).The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS).This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of 2.00.The results indicate that the LES model can reveal largescale vortex motion although with a larger grid-cell size.However,the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine grid.Overall,LES is a potential tool for simulating separated flow controlled by large-scale vortices. 展开更多
关键词 Large EDDY SIMULATION κ-ε model Backward-facing step Direct numerical SIMULATION Large-scale VORTICES Particle image VELOCIMETRY
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A numerical study on flame and large-scale flow structures in bluff-body stabilized flames
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作者 Jing CHEN Hua ZHOU Zhuyin REN 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第7期1646-1656,共11页
Large Eddy Simulations(LES) in conjunction with the Flamelet Progress Variable(FPV) approach have been performed to investigate the flame and large-scale flow structures in the bluff-body stabilized non-premixed flame... Large Eddy Simulations(LES) in conjunction with the Flamelet Progress Variable(FPV) approach have been performed to investigate the flame and large-scale flow structures in the bluff-body stabilized non-premixed flames, HM1 and HM3. The validity of the numerical methods is first verified by comparing the predicted velocity and composition fields with experimental measurements. Then the evolution of the flame and large-scale flow structures is analyzed when the flames approach blow-off. The analysis of instantaneous and statistical data indicates that there exists a shift of the control mechanism in the recirculation zone in the two flames. In the recirculation zone, HM1 flame is mainly controlled by the mixing effect and ignition mainly occurs in the outer shear layer. In HM3 flame, both the chemical reactions and mixing are important in the recirculation zone. The Proper Orthogonal Decomposition(POD) results show that the fluctuations in the outer shear layer are more intense in HM1, while the flow structures are more obvious in the outer vortex structure in HM3, due to the different control mechanism in the recirculation zone.It further shows that the flow structures in HM1 spread larger in the intense mixing zone due to higher temperature and less extinction. 展开更多
关键词 BLUFF-BODY stabilized FLAMES Large EDDY Simulation(LES) LARGE-SCALE flow structures PROPER ORTHOGONAL Decomposition(POD)
Exploration of the shared pathophysiological mechanisms of gestational diabetes and large for gestational age offspring 预览
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作者 Sofia Nahavandi Sarah Price +1 位作者 Priya Sumithran Elif Ilhan Ekinci 《世界糖尿病杂志:英文版(电子版)》 2019年第6期333-340,共8页
Gestational diabetes mellitus (GDM) and large for gestational age (LGA) offspring are two common pregnancy complications. Connections also exist between the two conditions, including mutual maternal risk factors for t... Gestational diabetes mellitus (GDM) and large for gestational age (LGA) offspring are two common pregnancy complications. Connections also exist between the two conditions, including mutual maternal risk factors for the conditions and an increased prevalence of LGA offspring amongst pregnancies affected by GDM. Thus, it is important to elucidate potential shared underlying mechanisms of both LGA and GDM. One potential mechanistic link relates to macronutrient metabolism. Indeed, derangement of carbohydrate and lipid metabolism is present in GDM, and maternal biomarkers of glucose and lipid control are associated with LGA neonates in such pregnancies. The aim of this paper is therefore to reflect on the existing nutritional guidelines for GDM in light of our understanding of the pathophysiological mechanisms of GDM and LGA offspring. Lifestyle modification is first line treatment for GDM, and while there is some promise that nutritional interventions may favourably impact outcomes, there is a lack of definitive evidence that changing the macronutrient composition of the diet reduces the incidence of either GDM or LGA offspring. The quality of the available evidence is a major issue, and rigorous trials are needed to inform evidence-based treatment guidelines. 展开更多
关键词 GESTATIONAL diabetes MELLITUS Large for GESTATIONAL age Metabolism Biomarkers GLUCOSE LIPIDS
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Samuel Madden and His Prophecy of the Large Companies in Modern Britain
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作者 张乃和 《世界史研究:英文版》 2019年第1期104-109,共6页
In 1733,Samuel Madden(1686-1765)anonymously published a book named Memoirs of the Twentieth Century.Some scholars have paid attention to the book,but there are few scholars who focused on Madden's prophecy about t... In 1733,Samuel Madden(1686-1765)anonymously published a book named Memoirs of the Twentieth Century.Some scholars have paid attention to the book,but there are few scholars who focused on Madden's prophecy about the large companies in twentieth-century Britain.And there are many disagreements among scholars about the nature of the book,which was composed of 17 letters pretended to be written in the late twentieth century.Some letters might be classified as a kind of science fiction or satire,but as a whole the book should be regarded as a new kind of utopian writing,even further as the early form of future history.Especially the last reply dated“London,Chelsea,Feb.24,1999”should be regarded as an independent text,and it gave us a vision of the corporate utopia or the utopia of company with its description of two large companies. 展开更多
关键词 Samuel Madden MEMOIRS of the Twentieth Century PROPHECY LARGE COMPANIES MODERN BRITAIN
ALK-positive anaplastic large cell lymphoma of the thoracic spine occurring in pregnancy: A case report 预览
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作者 Sen Yang Wei-Min Jiang Hui-Lin Yang 《世界临床病例杂志》 2019年第18期2857-2863,共7页
BACKGROUND Anaplastic large cell lymphoma (ALCL) is a type of non-Hodgkin’s lymphoma (NHL). ALCL is rare as a bone lesion and in pregnancy. CASE SUMMARY We present the first case of anaplastic lymphoma kinase (ALK)+ ... BACKGROUND Anaplastic large cell lymphoma (ALCL) is a type of non-Hodgkin’s lymphoma (NHL). ALCL is rare as a bone lesion and in pregnancy. CASE SUMMARY We present the first case of anaplastic lymphoma kinase (ALK)+ ALCL of the thoracic spine during pregnancy. A 25-year-old pregnant woman was presented to us at 24 wk’ gestation with severe back pain and weakness in the left lower limb. Imaging examination showed lesions at T10 and T11. She underwent posterior pedicle screw fixation and vertebroplasty. Pathological examination showed ALK+ ALCL. The patient chose to have therapeutic abortion after surgery and received chemotherapy in the hematology department. She now remains disease free with no neurological deficit after 30 mo’ follow-up. CONCLUSION ALK+ ALCL with the thoracic spine involvement is uncommon, especially in pregnancy. Many symptoms can be misunderstood during pregnancy;therefore, when a pregnant patient has persistent back pain or lower limb neurological symptoms, imaging examinations should be performed. 展开更多
关键词 ANAPLASTIC large cell LYMPHOMA PREGNANCY THORACIC SPINE Surgical treatment Chemotherapy Case report
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Diabase Sills in the Outer Zone of the Emeishan Large Igneous Province, Southwest China: Petrogenesis and Tectonic Implications
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作者 Yong Huang Chuan He +1 位作者 Neng-Song Chen Bin Xia 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第4期739-753,共15页
Compositionally and texturally zoned diabase dykes and sills occur in the outer zone of the Emeishan large igneous province(ELIP) in the southern Guizhou Province,Southwest China. Based on the detailed petrology,whole... Compositionally and texturally zoned diabase dykes and sills occur in the outer zone of the Emeishan large igneous province(ELIP) in the southern Guizhou Province,Southwest China. Based on the detailed petrology,whole rock geochemistry,zircon U-Pb geochronology and Hf isotopes and clinopyroxene mineral compositions studies,we investigate a representative diabase sill in the Luodian region with a view to understanding its petrogenesis and tectonic implications. Formed as composite zoned sub-volcanic intrusion,the diabase sill is characterized by gabbros and diabases in the inner zone and amygdaloidal diabases sporadically in the chilled zone within the upper sill margin. The diabasic and gabbroic rocks are composed of quartz-free and quartz-bearing groups. The quartz-free group rocks have low Si O2(45.7 wt.%–49.5 wt.%),moderate Mg O(5.66 wt.%–7.88 wt.%),high Ti O2(2.54 wt.%–3.65 wt.%),and Ti/Y values(536–747),corresponding to high-Ti type rocks. The quartz-bearing group rocks have higher Si O2(49.8 wt.%–51.7 wt.%) and lower Mg O(4.23 wt.%–4.74 wt.%),higher Ti O2(3.16 wt.%–3.63 wt.%),but lower Ti/Y values(399–419) than the quartz-free group ones,and thus belong to the low-Ti type. Both groups of rocks are enriched in LREE and LILE with negative Nb-Ta anomalies,and show broad tholeiitic affinity. The precursor magma of the high-Ti rocks might have originated from a source composed of mantle plume and subcontinental lithosphere mantle components,with minor crustal contamination during ascending. The magma of the low-Ti rocks was produced by mingling of the high-Ti diabasic rocks with minor injected intermediate-acidic magma plugs or blebs,suggesting magma mingling as one of the effective ways to change the high-Ti to low-Ti rocks of the ELIP. The diabasic sill underwent a rapid cooling event probably in response to a rapid tectonic uplift event,which probably occurred in the waning stage of ELIP during transition between the Middle and Late Permian after the domal uplift induced by the mantle-plume or 展开更多
关键词 DIABASE SILL high-Ti and low-Ti rocks PETROGENESIS tectonic evolution EMEISHAN large igneous province(ELIP) Guizhou
LARGE TIME BEHAVIOR OF SOLUTION TO NONLINEAR DIRAC EQUATION IN 1+1 DIMENSIONS 预览
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作者 张永前 赵勤 《数学物理学报:B辑英文版》 SCIE CSCD 2019年第2期597-606,共10页
This paper studies the large time behavior of solution for a class of nonlinear massless Dirac equations in R1+1. It is shown that the solution will tend to travelling wave solution when time tends to infinity.
关键词 large time behavior NONLINEAR DIRAC EQUATION gross-Neveu model global STRONG SOLUTION gravelling wave SOLUTION
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CFD simulation of tidal current farm by using AL model 预览
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作者 Cheng Liu Changhong Hu 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第1期34-40,共7页
In this study,an efficient numerical method for predicting the wake interference of multiple turbines is presented.The actuator line (AL) model instead of the geometry-resolved method is adopted to represent the rotor... In this study,an efficient numerical method for predicting the wake interference of multiple turbines is presented.The actuator line (AL) model instead of the geometry-resolved method is adopted to represent the rotor.The large-eddy simulation (LES) is performed to predict wakes of multiple turbines operated in turbulent flows.An efficient immersed boundary (IB) method with moving least square reconstruction (MLS) is developed to model the nacelle and support structure of the tidal turbine.A simple wall function based on the MLS-IB method and boundary-layer equations is employed to compute the instantaneous wall shear stress.Laminar flow simulations of unsteady flows past a cylinder illustrate the accuracy of the wall function IB method.Finally,the proposed method is extended to study turbulent flow past tandem tidal rotors,in which the wake profile behind rotors is analyzed.The results are found to be in reasonable agreement with published data. 展开更多
关键词 TIDAL current FARM immersed BOUNDARY method wall fimction MODEL large EDDY simulation (LES) ACTUATOR line MODEL
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再保险能降低财产保险公司的风险承担吗?——基于大中小型财险公司的比较 预览
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作者 牛雪舫 《保险职业学院学报》 2019年第3期55-58,共4页
再保险能够分散保险经营主体的经营风险,这是再保险产生和发展的理论基础。本文基于我国48家财产保险公司的经营数据,并按照资产规模,将其分为大中小型,比较了再保险对于分散不同类型的财产保险公司经营风险的作用。实证研究发现,在大... 再保险能够分散保险经营主体的经营风险,这是再保险产生和发展的理论基础。本文基于我国48家财产保险公司的经营数据,并按照资产规模,将其分为大中小型,比较了再保险对于分散不同类型的财产保险公司经营风险的作用。实证研究发现,在大型的财产保险公司中,再保险能够显著地降低风险承担,而在小型的财产公司中,并未起到降低经营风险的作用。因而,相比于欧美等发达国家,我国的再保险机制的运用尚未成熟。 展开更多
关键词 再保险 风险承担 大中小型 尚未成熟
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Asymptotic Behaviors for Critical Branching Processes with Immigration
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作者 Dou Dou LI Mei ZHANG 《数学学报:英文版》 SCIE CSCD 2019年第4期537-549,共13页
In this paper, we investigate the asymptotic behaviors of the critical branching process with immigration {Zn, n ≥ 0}. First we get some estimation for the probability generating function of Zn. Based on it, we get a... In this paper, we investigate the asymptotic behaviors of the critical branching process with immigration {Zn, n ≥ 0}. First we get some estimation for the probability generating function of Zn. Based on it, we get a large deviation for Zn+1/Zn. Lower and upper deviations for Zn are also studied. As a by-product, an upper deviation for max1≤i≤n Zi is obtained. 展开更多
关键词 CRITICAL branching PROCESS IMMIGRATION LARGE DEVIATIONS
Boundary Behavior of Large Solutions to the Monge-Ampere Equation in a Borderline Case
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作者 Zhi Jun ZHANG 《数学学报:英文版》 SCIE CSCD 2019年第7期1190-1204,共15页
This paper is concerned with the boundary behavior of strictly convex large solutions to the Monge-Ampere equation detD^2u{x)= b(x)f(u(x)),u> 0, x∈Ω, where Ω is a strictly convex and bounded smooth domain in R^N... This paper is concerned with the boundary behavior of strictly convex large solutions to the Monge-Ampere equation detD^2u{x)= b(x)f(u(x)),u> 0, x∈Ω, where Ω is a strictly convex and bounded smooth domain in R^N with N ≥ 2, f is normalized regularly varying at infinity with the critical index N and has a lower term, and b∈C^∞(Ω) is positive in Ω, but may be appropriate singular on the boundary. 展开更多
关键词 The Monge-Ampere EQUATIONS STRICTLY CONVEX large solutions a BORDERLINE CASE BOUNDARY behavior
Simulation of a high-performance enhancement-mode HFET with back-to-back graded AlGaN layers
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作者 Fu PENG Chao YANG +4 位作者 Siyu DENG Dongya OUYANG Bo ZHANG Jie WEI Xiaorong LUO 《中国科学:信息科学(英文版)》 SCIE EI CSCD 2019年第6期87-97,共11页
A novel three-dimensional hole gas(3 DHG) enhancement-mode(E-mode) heterostructure fielde?ect transistor(HFET) is proposed and investigated. It features back-to-back graded AlGaN(BGA) barrier layers consisting of a po... A novel three-dimensional hole gas(3 DHG) enhancement-mode(E-mode) heterostructure fielde?ect transistor(HFET) is proposed and investigated. It features back-to-back graded AlGaN(BGA) barrier layers consisting of a positive-graded AlGaN layer and a negative-graded AlGaN layer, which form polarization gradient and subsequently induce the three-dimensional electron gas(3 DEG) and 3 DHG in the positiveand negative-graded AlGaN layers, respectively. The source and drain are located at the same side of the metal-insulator-semiconductor(MIS) trench gate, and the source is in contact with the HfO2 gate insulator.First, the on-state current is significantly improved owing to the high-density 3 DEG in the positive-graded AlGaN. Next, the vertical conductive channel between the source and 3 DEG is blocked by the 3 DHG, thereby realizing the E-mode. The threshold voltage(Vth) can be modulated by a partial doping conductive channel.Subsequently, a high breakdown voltage(BV) is obtained, because the polarization junction formed by the polarization charges assists in depleting the drift region in the o?-state. Next, the BGA-HFET is smaller than the conventional HFET(Con-HFET) owing to the special location of the source. The BV of the proposed HFET sharply increases to 919 V from 39 V of the Con-HFET with the same gate-drain spacing, and the saturation drain current is increased by 103.5%. 展开更多
关键词 GRADED ALGAN 3DHG-3DEG large on-state current high voltage enhancement mode
Strong Laws of Large Numbers for Double Sums of Banach Space Valued Random Elements
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作者 Robert PARKER Andrew ROSALSKY 《数学学报:英文版》 SCIE CSCD 2019年第5期583-596,共14页
For a double array {Vm,n, m≥1,n≥1} of independent, mean 0 random elements in a real separable Rademacher type p (1≤p≤ 2) Banach space and an increasing double array {bm,n, m≥1,n ≥ 1} of positive constants, the l... For a double array {Vm,n, m≥1,n≥1} of independent, mean 0 random elements in a real separable Rademacher type p (1≤p≤ 2) Banach space and an increasing double array {bm,n, m≥1,n ≥ 1} of positive constants, the limit law max1≤k≤m,1≤l≤n||Σi/^k=1Σj/^l=1Vi,j||/bm,n → 0 a.c. and in Lp as m ∨n →∞ is shown to hold if Σm/^∞=1Σn/^∞=1E||Vm,n||^p/bm,n/^p<∞. This strong law of large numbers provides a complete characterization of Rademacher type p Banach spaces. Results of this form are also established when 0<p≤1 where no independence or mean 0 conditions are placed on the random elements and without any geometric conditions placed on the underlying Banach space. 展开更多
关键词 Real separable BANACH SPACE DOUBLE array of independent random elements strong law of large numbers almost sure CONVERGENCE Rademacher type p BANACH SPACE CONVERGENCE in Lp
日本自由贸易战略的新动向及其影响 预览
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作者 贺平 《中国国际问题研究:英文版》 2019年第1期121-137,共17页
In recent years,two significant trends have emerged in global trade.On one hand,based on the unilateral idea that puts their respective national interests first,a few countries have retreated from the position of equa... In recent years,two significant trends have emerged in global trade.On one hand,based on the unilateral idea that puts their respective national interests first,a few countries have retreated from the position of equal and mutually beneficial trade,even at the cost of fierce trade frictions with other nations.On the other hand,several large economies have adopted a positive attitude toward their free trade strategies and are endeavoring to establish“mega-free trade agreements.” 展开更多
关键词 贸易战略 OTHER 自由 日本 HAVE FIRST LARGE IDEA
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Ceftriaxone-induced immune hemolytic anemia in a case with large vestibular aqueduct syndrome after cochlear implant
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作者 Yu Wang Tao Pan +6 位作者 Fu-Rong Ma Ji-Jun Wang Ke Zhang Wei-Wei Pan Jing-Hui Zhang Zhan-Miao Yi Ying-Qiu Ying 《中华医学杂志:英文版》 SCIE CAS CSCD 2019年第1期100-102,共3页
To the Editor:Drug-induced immune hemolytic anemia (DIIHA)is a rare but severe condition.Ceftriaxone,a third-generation cephalosporin with a wide antibacterial spectrum and effective antibacterial action,is one of the... To the Editor:Drug-induced immune hemolytic anemia (DIIHA)is a rare but severe condition.Ceftriaxone,a third-generation cephalosporin with a wide antibacterial spectrum and effective antibacterial action,is one of the most common drugs causing DIIHA.^[1]Ceftriaxoneinduced immune hemolytic anemia (CIIHA)is a potentially fatal complication.^[2]Most of the patients were children.The reported fatality rate of CIIHA was as high as 40%. 展开更多
关键词 Ceftriaxone-induced immune HEMOLYTIC anemia large VESTIBULAR AQUEDUCT syndrome cochlear implant
Entire Large Solutions to Semilinear Elliptic Systems of Competitive Type
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作者 LAIR Alan V. 《偏微分方程:英文版》 CSCD 2019年第1期52-65,共14页
We consider the elliptic system △u = p(|x|)u^av^b,△v=q(|x|)u^cv^d on R^n (n≥3) where a, b, c, d are nonnegative constants with max{a,d}≤ 1, and the functions p and q are nonnegative, continuous, and the support of... We consider the elliptic system △u = p(|x|)u^av^b,△v=q(|x|)u^cv^d on R^n (n≥3) where a, b, c, d are nonnegative constants with max{a,d}≤ 1, and the functions p and q are nonnegative, continuous, and the support of min{p(r),q(r)} is not compact. We establish conditions on p and q, along with the exponents a, bf c, d, which ensure the existence of a positive entire solution satisfying lim|x|→∞u(x)=lim|x|→∞v (x)=∞. 展开更多
关键词 LARGE SOLUTION entire SOLUTION SEMILINEAR ellipticsystem
Complex multiple-segment ruptures of the 28 September 2018, Sulawesi, Indonesia, earthquake
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作者 Yong Zhang Yun-Tai Chen Wanpeng Feng 《科学通报:英文版》 SCIE EI CSCD 2019年第10期650-652,共3页
On 28 September 201 & an A4W7.5 earthquake struck Palu, Indonesia, and caused a large number of deaths and economic losses. Seismic moment tensor solutions determined by different institutes consistently suggest t... On 28 September 201 & an A4W7.5 earthquake struck Palu, Indonesia, and caused a large number of deaths and economic losses. Seismic moment tensor solutions determined by different institutes consistently suggest that this earthquake is overall a strike-slip event. However, it caused an unexpected large-scale tsunami around the Palu bay area. Commonly, the displacements of hanging wall and foot wall of a strike-slip event are mainly in horizontal directions, and are considerably weak in vertical components. Since vertical deformations are critical for tsunami generations, it is necessary to identify whether the tsunami is related to the source process or not. For this purpose, investigations of the source process are needed [1]. 展开更多
关键词 EARTHQUAKE struck CAUSED a LARGE SOURCE process
Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence 预览
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作者 Pedro Xavier Ramos Laurent Schindfessel +1 位作者 Joao Pedro Pego Tom De Mulder 《水科学与水工程:英文版》 EI CAS CSCD 2019年第3期235-243,共9页
Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized co... Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently. 展开更多
关键词 Open channel CONFLUENCE BED ELEVATION DISCORDANCE Three-dimensional numerical MODELLING Large EDDY simulation Recirculation zone
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A dual timescale model for micro-mixing and its application in LES-TPDF simulations of turbulent nonpremixed flames
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作者 Fang WANG Rui LIU +2 位作者 Li DOU Denghuan LIU Jie JIN 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第4期875-887,共13页
The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transp... The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The Aero-Engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory’s methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames. 展开更多
关键词 DUAL TIME scale MODEL Large EDDY simulation Sandia methane-air jet ?ame TPDF molecular mixing MODEL Turbulence combustion MODEL
大型6列往复式氢气压缩机的开发研制 预览
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作者 张欣 韩卫国 +4 位作者 杨成炯 韩玉昌 张小建 任希文 钱则刚 《石油化工设备技术》 CAS 2019年第2期27-30,I0002共5页
随着石化工业装置大型化,往复式压缩机呈现出大型化和多列化的发展趋势。近年来,我国大型往复式压缩机开发和应用取得了长足进步,压缩机活塞杆最大允许连续负荷(或最大允许活塞力)已由800kN、1250kN发展到1500kN,但是在炼油装置中大型... 随着石化工业装置大型化,往复式压缩机呈现出大型化和多列化的发展趋势。近年来,我国大型往复式压缩机开发和应用取得了长足进步,压缩机活塞杆最大允许连续负荷(或最大允许活塞力)已由800kN、1250kN发展到1500kN,但是在炼油装置中大型往复式压缩机列数仍局限于4列。依托中国石化塔河炼化60万t/a连续重整装置,自主开发研制6M80大型往复式氢气压缩机,实现了大型6列往复式压缩机的国产化。凭借先进的计算辅助设计手段以及领先的关键技术特征,压缩机运行稳定可靠。该机型的开发研制,形成了具有独立自主知识产权产品,可替代进口,降低了设备投资、交货周期及维修成本,具有较好的经济和社会效益。 展开更多
关键词 往复式压缩机 氢气压缩机 大型 6M(HE)80 6列 开发研制
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