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通过一个等价雷诺数揭示层流到湍流的转捩区域 Article

陈晓东

《工程（英文）》 2019年 第5卷 第3期   页码 576-579 doi: 10.1016/j.eng.2018.09.013

摘要：

Flow transition from laminar to turbulent mode (and vice versa)—that is, the initiation of turbulence—is one of the most important research subjects in the history of engineering. Even for pipe flow, predicting the onset of turbulence requires sophisticated instrumentation and/or direct numerical simulation, based on observing the instantaneous flow structure formation and evolution. In this work, a local Reynolds number equivalence γ (ratio of local inertia effect to viscous effect) is seen to conform to the Universal Law of the Wall, where γ = 1 represents a quantitative balance between the abovementioned two effects. This coincides with the wall layer thickness (y+ = 1, where y+ is the dimensionless distance from the wall surface defined in the Universal Law of the Wall). It is found that the characteristic of how the local derivative of γ against the local velocity changes with increasing velocity determines the onset of turbulence. For pipe flow, γ ≈ 25, and for plate flow, γ ≈ 151.5. These findings suggest that a certain combination of γ and velocity (nonlinearity) can qualify the source of turbulence (i.e., generate turbulent energy). Similarly, a re-evaluation of the previous findings reveals that only the geometrically narrow domain can act locally as the source of turbulence, with the rest of the flow field largely being left for transporting and dissipating. This understanding will have an impact on the future large-scale modeling of turbulence.

关键词： 局部等价雷诺数     转捩     壁面律     管流     平板流动     建模    

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Convective heat transfer in helical coils for constant-property and variable-property flows with high Reynolds

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

《能源前沿（英文）》 2010年 第4卷 第4期   页码 546-552 doi: 10.1007/s11708-010-0116-8

摘要： Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10 mm, coil diameter of 300 mm, and pitch of 50 mm. The experiments were conducted over a wide Reynolds number range of 40000 to 500000. Both constant-property flows at normal pressure and variable-property flows at supercritical pressure were investigated. The contribution of secondary flow in the helical coil to heat transfer was gradually suppressed with increasing Reynolds number. Hence, heat transfer coefficients of the helical tube were close to those of the straight tube under the same flow conditions when the Reynolds number is large enough. Based on the experimental data, heat transfer correlations for both incompressible flows and supercritical fluid flows through helical coils were proposed.

关键词： convective heat transfer     helical coils     high Reynolds number     supercritical pressure     variable property    

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A numerical study of non-Darcy flow in EGS heat reservoirs during heat extraction

Wenjiong CAO, Wenbo HUANG, Guoling WEI, Yunlong JIN, Fangming JIANG

《能源前沿（英文）》 2019年 第13卷 第3期   页码 439-449 doi: 10.1007/s11708-019-0612-4

摘要： Underground non-Darcy fluid flow has been observed and investigated for decades in the petroleum industry. It is deduced by analogy that the fluid flow in enhanced geothermal system (EGS) heat reservoirs may also be in the non-Darcy regime under some conditions. In this paper, a transient 3D model was presented, taking into consideration the non-Darcy fluid flow in EGS heat reservoirs, to simulate the EGS long-term heat extraction process. Then, the non-Darcy flow behavior in water- and supercritical CO (SCCO )-based EGSs was simulated and discussed. It is found that non-Darcy effects decrease the mass flow rate of the fluid injected and reduce the heat extraction rate of EGS as a flow resistance in addition to the Darcy resistance which is imposed to the seepage flow in EGS heat reservoirs. Compared with the water-EGS, the SCCO -EGS are more prone to experiencing much stronger non-Darcy flow due to the much larger mobility of the SCCO . The non-Darcy flow in SCCO - EGSs may thus greatly reduce their heat extraction performance. Further, a criterion was analyzed and proposed to judge the onset of the non-Darcy flow in EGS heat reservoirs. The fluid flow rate and the initial thermal state of the reservoir were taken and the characteristic Forchheimer number of an EGS was calculated. If the calculated Forchheimer number is larger than 0.2, the fluid flow in EGS heat reservoirs experiences non-negligible non-Darcy flow characteristic.

关键词： enhanced geothermal system     non-Darcy flow     heat extraction     Reynolds number     Forchheimer number    

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Experiment and surge analysis of centrifugal two-stage turbocharging system

HE Yituan, MA Chaochen

《机械工程前沿（英文）》 2008年 第3卷 第4期   页码 365-368 doi: 10.1007/s11465-008-0073-7

摘要： To study a centrifugal two-stage turbocharging system’s surge and influencing factors, a special test bench was set up and the system surge test was performed. The test results indicate that the measured parameters such as air mass flow and rotation speed of a high pressure (HP) stage compressor can be converted into corrected parameters under a standard condition according to the Mach number similarity criterion, because the air flow in a HP stage compressor has entered the Reynolds number () auto-modeling range. Accordingly, the reasons leading to a two-stage turbocharging system’s surge can be analyzed according to the corrected mass flow characteristic maps and actual operating conditions of HP and low pressure (LP) stage compressors.

关键词： auto-modeling     compressor     Reynolds number     characteristic     standard condition    

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Experimental study on heat transfer characteristics of supercritical carbon dioxide in horizontal tube

LV Jing, FU Meng, QIN Na, DONG Bin

《能源前沿（英文）》 2008年 第2卷 第3期   页码 339-343 doi: 10.1007/s11708-008-0045-y

摘要： The heat transfer characteristics of supercritical carbon dioxide in a horizontal tube with water in the vertical cross flow form were experimentally investigated. The results indicate that the changes of inlet pressure, mass flow rate, and cooling water flow rate have major effects on heat transfer performance. The variations of Reynolds number and Prandtl number were obtained in counter flow and vertical cross flow. The four conventional correlations for convection heat transfer of supercritical carbon dioxide were verified by the experimental data in this study and the correlation agree with this experimental condition was determined.

关键词： conventional     experimental condition     vertical     Reynolds number     transfer    

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Kinetic energy based model assessment and sensitivity analysis of vortex induced vibration of segmental bridge decks

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2017年 第11卷 第4期   页码 480-501 doi: 10.1007/s11709-017-0435-5

摘要： In this paper, semi 3D models for segmental Bridge decks are created in ABAQUS CFD program with the support of MATLAB codes to simulate and analyze vortex shedding generated due to wind excitation through considering the stationary position of the deck. Three parameters (wind speed, deck streamlined length and dynamic viscosity of the air) are dedicated to study their effects on the kinetic energy of the system in addition to the shapes and patterns of the vortices. Two benchmarks from the literature Von Karman and Dyrbye and Hansen are considered to validate the vortex shedding aspects for the CFD models. Good agreement between the results of the benchmarks and the semi 3D models has been detected. Latin hypercube experimental method is dedicated to generate the surrogate models for the kinetic energy of the system and the lift forces. Variance based sensitivity analysis is utilized to calculate the main sensitivity indices and the interaction orders for all the three parameters. The kinetic energy approach performed very well in revealing the rational effects and the roles of each parameter in the generation of vortex shedding and predicting vortex induced vibration of the deck.

关键词： vortex induced vibration     reynolds number     kinetic energy     vorticity     latin hypercube sampling    

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千米级斜拉桥空气动力学问题

陈艾荣,马如进,王达磊

《中国工程科学》 2009年 第11卷 第3期   页码 31-37

摘要：

以苏通大桥为背景，对超大跨径斜拉桥的空气动力学问题进行了研究，着重讨论了超大跨径斜拉桥的动力特性、风荷载、基于气弹模型的颤振导数识别、结构体系以及涡激振动特性等一系列问题。研究结果表明，考虑侧向风荷载作用下斜拉索的非线性效应之后，全桥结构的竖向刚度有折减现象。同时发现Fixed - Fixed体系是解决顺桥向风荷载的有效途径还提出了基于气弹模型的颤振导数识别方法，并就斜拉桥的涡激振动和雷诺数效应进行了探讨。

关键词： 苏通大桥斜拉桥     动力特性     合理体系     雷诺数效应     颤振导数    

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Numerical simulation of fluid dynamics in the stirred tank by the SSG Reynolds Stress Model

Nana QI, Hui WANG, Kai ZHANG, Hu ZHANG

《化学科学与工程前沿（英文）》 2010年 第4卷 第4期   页码 506-514 doi: 10.1007/s11705-010-0508-7

摘要： The Speziale, Sarkar and Gatski Reynolds Stress Model (SSG RSM) is utilized to simulate the fluid dynamics in a full baffled stirred tank with a Rushton turbine impeller. Four levels of grid resolutions are chosen to determine an optimised number of grids for further simulations. CFD model data in terms of the flow field, trailing vortex, and the power number are compared with published experimental results. The comparison shows that the global fluid dynamics throughout the stirred tank and the local characteristics of trailing vortices near the blade tips can be captured by the SSG RSM. The predicted mean velocity components in axial, radial and tangential direction are also in good agreement with experiment data. The power number predicted is quite close to the designed value, which demonstrates that this model can accurately calculate the power number in the stirred tank. Therefore, the simulation by using a combination of SSG RSM and MRF impeller rotational model can accurately model turbulent fluid flow in the stirred tank, and it offers an alternative method for design and optimisation of stirred tanks.

关键词： stirred tank     fluid dynamics     numerical simulation     SSG Reynolds Stress Model     MRF    

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鞭毛/纤毛内在驱动机制启发的一体式管状机器人驱动器 Article

苗佳麒, 张铁山, 李根, 郭栋, 孙思琦, 谭蓉, 史家海, 申亚京

《工程（英文）》 2023年 第23卷 第4期   页码 170-180 doi: 10.1016/j.eng.2022.09.014

摘要：

鞭毛和纤毛独特的运动模式（如鞭毛的平面/螺旋波形式推进和纤毛的二维/三维不对称搏动）在众多生物的生命活动中起到至关重要的作用，这也启发了诸多仿生设计，尤其对于微型机器人系统。然而，与自然界中微生物能够从统一化的9 + 2 轴丝生物结构中进化出多种运动模式不同的是，当前的仿生学仍然没有有效的工程策略去实现这样的智慧。在此，我们通过研究鞭毛和纤毛的内部结构及其内在驱动机制，推导出了一个统一的物理模型来描述微管弯曲及其所构建的宏观鞭毛/纤毛运动。基于该模型，我们进而提出了基于三通道的管状驱动概念，并相应地通过杆嵌入铸造工艺制造了一个三通道的管状驱动器。通过编程不同通道的驱动模式，这一管状驱动器不仅可以再现自然界中多样的二维及三维鞭毛/纤毛运动，还可以延展出更多的非对称纤毛搏动模式以实现低雷诺数下的有效推进。该研究加深了我们对微生物推进机制的理解，为仿生系统的设计提供了新灵感，并有望在广泛的工程领域中寻找到重要的应用场景。

关键词： 仿生系统     软体驱动器     9 + 2结构     人工纤毛     低雷诺数    

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Combined use of inoculation and low phosphorus application increased plant growth, root nodulation and grain yield of common bean () in Ethiopia

《农业科学与工程前沿（英文）》 doi: 10.15302/J-FASE-2024556

摘要：

● Two bean cultivars responded strongly to Rhizobium inoculation in both 2012 and 2013, relative to uninoculated control.

关键词： Bean cultivars     grain yield     Hawassa Dume     Ibbado     nodule dry matter     nodule number     pod number per plant     seed number per pod     shoot biomass    

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Estimating the number of Chinese cancer patients eligible for and benefit from immune checkpoint inhibitors

《医学前沿（英文）》 2022年 第16卷 第5期   页码 773-783 doi: 10.1007/s11684-021-0902-1

摘要： The total number of cancer patients who are eligible for and will benefit from immune checkpoint inhibitors (ICIs) in China has not been quantified. This cross-sectional study was conducted to estimate the number of Chinese cancer patients with eligibility and response to ICIs based on the 2015 Chinese cancer statistics and the immune checkpoint inhibitor clinical practice guideline of the Chinese Society of Clinical Oncology. A total of 11 ICIs were recommended for 17 cancer types. The estimated number of eligible patients annually was 1 290 156 (55.18%), which included 888 738 males (60.05%) and 400 468 females (46.67%). The estimated number of responders annually was 448 972 (19.20%), which included 309 023 males (20.88%) and 139 764 females (16.29%). Gastric cancer (n=291 000, 12.45%), non-small-cell lung cancer (n=289 629, 12.39%), and hepatocellular carcinoma (n=277 100, 11.85%) were the top three cancer types with the highest number of eligible patients. Non-small-cell lung cancer (n=180 022, 7.70%), hepatocellular carcinoma (n=75 648, 3.24%), and small-cell lung cancer (n=64 362, 2.75%) were the top three cancer types with the highest number of responders. In conclusion, ICIs provide considerable benefit in Chinese cancer patients under optimal estimation.

关键词： benefit     China     eligibility     immune checkpoint inhibitor     public health    

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Identification of structural parameters and boundary conditions using a minimum number of measurement

Ali KARIMPOUR, Salam RAHMATALLA

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1331-1348 doi: 10.1007/s11709-020-0686-4

摘要： This article proposes a novel methodology that uses mathematical and numerical models of a structure to build a data set and determine crucial nodes that possess the highest sensitivity. Regression surfaces between the structural parameters and structural output features, represented by the natural frequencies of the structure and local transmissibility, are built using the numerical data set. A description of a possible experimental application is provided, where sensors are mounted at crucial nodes, and the natural frequencies and local transmissibility at each natural frequency are determined from the power spectral density and the power spectral density ratios of the sensor responses, respectively. An inverse iterative process is then applied to identify the structural parameters by matching the experimental features with the available parameters in the myriad numerical data set. Three examples are presented to demonstrate the feasibility and efficacy of the proposed methodology. The results reveal that the method was able to accurately identify the boundary coefficients and physical parameters of the Euler-Bernoulli beam as well as a highway bridge model with elastic foundations using only two measurement points. It is expected that the proposed method will have practical applications in the identification and analysis of restored structural systems with unknown parameters and boundary coefficients.

关键词： structural model validation     eigenvalue problem     response surface     inverse problems    

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Numerical analysis of aerodynamic noise radiated from cross flow fan

CHEN Anbang, LI Song, HUANG Dongtao

《能源前沿（英文）》 2008年 第2卷 第4期   页码 443-447 doi: 10.1007/s11708-008-0063-9

摘要： The flow field in a cross flow fan was simulated by solving the 2-D unsteady Reynolds-averaged Navier-Stokes equations. The calculated pressure fluctuations of the blades, the vortex wall, and the rear wall were then used as noise sources to calculate the sound field. The Ffowcs Williams-Hawkings (FW-H) equation was employed to predict the noise field caused by these sources. The predictions show that the rear wall and the vortex wall sources contribute significantly to the total noise and that both the predicted aerodynamic performance and noise agree well with the experimental results.

关键词： predicted aerodynamic     Williams-Hawkings     calculated pressure     aerodynamic performance     unsteady Reynolds-averaged    

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Influence of cetane number improver on performance and emissions of a common-rail diesel engine fueled

Wu YU, Gen CHEN, Zuohua HUANG

《能源前沿（英文）》 2011年 第5卷 第4期   页码 412-418 doi: 10.1007/s11708-011-0163-9

摘要： In this paper, the effect of cetane number (CN) improver on performance and emissions, including particulate number concentration and size distribution, of a turbocharged, common-rail diesel engine fueled with biodiesel-methanol were studied. Two volume fractions (0.3% and 0.6%) of CN improver were added to BM30 (30% of methanol in the biodiesel-methanol blend) in the experiment. The results show that, compared with those of biodiesel-methanol blend, the peak value of cylinder pressure increases, the second peak of heat release rate decreases, the start of second heat release are advanced, and the fuel economy and thermal efficiency are improved when CN improver is added to biodiesel-methanol blend. Besides, CO and HC emissions decrease, NO emission varies little and smoke emissions increase slightly. Moreover, exhaust particles of BM30 mainly distribute in nano-size range. Furthermore, particle number concentration decreases and peak of size distribution profile shifts toward large size direction.

关键词： biodiesel     methanol     common-rail (CR) diesel engine     cetane number (CN) improver    

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Iteration framework for solving mixed lubrication computation problems

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 635-648 doi: 10.1007/s11465-021-0632-8

摘要： The general discrete scheme of time-varying Reynolds equation loses the information of the previous step, which makes it unreasonable. A discretization formula of the Reynolds equation, which is based on the Crank–Nicolson method, is proposed considering the physical message of the previous step. Gauss–Seidel relaxation and distribution relaxation are adopted for the linear operators of pressure during the numerical solution procedure. In addition to the convergent criteria of pressure distribution and load, an estimation framework is developed to investigate the relative error of the most important term in the Reynolds equation. Smooth surface with full contacts and mixed elastohydrodynamic lubrication is tested for validation. The asperity contact and sinusoidal wavy surface are examined by the proposed discrete scheme. Results show the precipitous decline in the boundary of the contact area. The relative error suggests that the pressure distribution is reliable and reflects the accuracy and effectiveness of the developed method.

关键词： mixed lubrication     discretization formula     relative error     Reynolds equation     asperity    

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标题 作者 时间 类型 操作

通过一个等价雷诺数揭示层流到湍流的转捩区域

陈晓东

期刊论文

Convective heat transfer in helical coils for constant-property and variable-property flows with high Reynolds

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

期刊论文

A numerical study of non-Darcy flow in EGS heat reservoirs during heat extraction

Wenjiong CAO, Wenbo HUANG, Guoling WEI, Yunlong JIN, Fangming JIANG

期刊论文

Experiment and surge analysis of centrifugal two-stage turbocharging system

HE Yituan, MA Chaochen

期刊论文

Experimental study on heat transfer characteristics of supercritical carbon dioxide in horizontal tube

LV Jing, FU Meng, QIN Na, DONG Bin

期刊论文

Kinetic energy based model assessment and sensitivity analysis of vortex induced vibration of segmental bridge decks

Nazim Abdul NARIMAN

期刊论文

千米级斜拉桥空气动力学问题

陈艾荣,马如进,王达磊

期刊论文

Numerical simulation of fluid dynamics in the stirred tank by the SSG Reynolds Stress Model

Nana QI, Hui WANG, Kai ZHANG, Hu ZHANG

期刊论文

鞭毛/纤毛内在驱动机制启发的一体式管状机器人驱动器

苗佳麒, 张铁山, 李根, 郭栋, 孙思琦, 谭蓉, 史家海, 申亚京

期刊论文

Combined use of inoculation and low phosphorus application increased plant growth, root nodulation and grain yield of common bean () in Ethiopia

期刊论文

Estimating the number of Chinese cancer patients eligible for and benefit from immune checkpoint inhibitors

期刊论文

Identification of structural parameters and boundary conditions using a minimum number of measurement

Ali KARIMPOUR, Salam RAHMATALLA

期刊论文

Numerical analysis of aerodynamic noise radiated from cross flow fan

CHEN Anbang, LI Song, HUANG Dongtao

期刊论文

Influence of cetane number improver on performance and emissions of a common-rail diesel engine fueled

Wu YU, Gen CHEN, Zuohua HUANG

期刊论文

Iteration framework for solving mixed lubrication computation problems

期刊论文