检索结果-南通市图书馆

Chinese Journal of Aeronautics 2024年第7期37卷 109-133页

作者： Jianfei WEI Silong ZHANG Jingying ZUO Xin LI Jiang QIN Wen BAO School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Supersonic fuel film cooling is a promising way to simultaneously reduce the severe wall heat and friction load of the internal passage in a scramjet engine when operating at hypersonic *** eddy simulations were performed to investigate the cooling and wall friction characteristics of hydrogen and hydrocarbon films under inert and reactive *** results show that the essential difference of the turbulent state in the mixing layer contributes to the totally different behaviors of the cooling and wall friction reduction performances of the two fuel *** turbulent transport processes between the hydrogen film and the mainstream are much weaker as compared to the case of hydrocarbon film,making inert hydrogen rather superior in cooling and friction reduction ***,the increase of wall temperature for hydrogen film under the inert case is mainly driven by the loss of hydrogen with high heat capacity instead of by direct heat ***,the film cooling performance severely deteriorates when the hydrogen film burns due to presence of severe heat release sources near the *** the other hand,combustion of hydrocarbon film in the boundary layer can remarkably improve its originally barely-satisfactory cooling and friction reduction performance to the level comparable to that of hydrogen film,due to the suppression of turbulent transport processes in the mixing layer and presence of heat absorption sources near the ***,the hydrogen film is more advantageous in friction reduction,while the hydrocarbon film is more suitable for cooling.

关键词： Supersonic film cooling Hydrogen Hydrocarbon Boundary layer combustion large eddy simulation

large eddy simulation of flow over a three-dimensional hill with different slope angles

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2024年第1期18卷 98-111页

作者： Liang LI Deqian ZHENG Guixiang CHEN Pingzhi FANG Wenyong MA Shengming TANG School of Civil Engineering Henan University of TechnologyZhengzhou 450001China Henan International Joint Laboratory of Modern Green Ecological Storage System Zhengzhou 450001China Henan Key Laboratory of Grain Storage Facility and Safety Zhengzhou 450001China Shanghai Typhoon Institute of China Meteorological Administration Shanghai 200030China Wind Engineering Research Center Shijiazhuang Tiedao UniversityShijiazhuang 050043China

Slope variation will significantly affect the characteristics of the wind field around a *** paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field *** slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill *** inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation *** time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively *** accuracy of the present method is verified by comparison with experimental *** slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be *** fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle *** increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of *** vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.

关键词： large eddy simulation inflow turbulence topographic wind field critical slope flow mechanism

large eddy simulation of Vertical Structure and Size Density of Deep Layer Clouds

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第8期41卷 1629-1642,1668-1670页

作者： Bangjun CAO Xianyu YANG Jun WEN Qin HU Ziyuan ZHU School of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610225China Institute for Geophysics and Meteorology University of CologneCologne 50923Germany

In a convective scheme featuring a discretized cloud size density, the assumed lateral mixing rate is inversely proportional to the exponential coefficient of plume size. This follows a typical assumption of-1, but it has unveiled inherent uncertainties, especially for deep layer clouds. Addressing this knowledge gap, we conducted comprehensive large eddy simulations and comparative analyses focused on terrestrial regions. Our investigation revealed that cloud formation adheres to the tenets of Bernoulli trials, illustrating power-law scaling that remains consistent regardless of the inherent deep layer cloud attributes existing between cloud size and the number of clouds. This scaling paradigm encompasses liquid, ice, and mixed phases in deep layer clouds. The exponent characterizing the interplay between cloud scale and number in the deep layer cloud, specifically for liquid, ice, or mixed-phase clouds, resembles that of shallow convection,but converges closely to zero. This convergence signifies a propensity for diminished cloud numbers and sizes within deep layer clouds. Notably, the infusion of abundant moisture and the release of latent heat by condensation within the lower atmospheric strata make substantial contributions. However, this role in ice phase formation is limited. The emergence of liquid and ice phases in deep layer clouds is facilitated by the latent heat and influenced by the wind shear inherent in the middle levels. These interrelationships hold potential applications in formulating parameterizations and post-processing model outcomes.

关键词： deep layer cloud cloud spatial structure cloud size density large eddy simulation

Influence of the Acoustic Liner in large eddy simulation of Longitudinal Thermoacoustic Instability in a Model Annular Combustor

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2024年第2期33卷 710-724页

作者： MENG Sheng ZHANG Man GAO Yi AECC Commercial Aircraft Engine Co. Ltd.Shanghai200241China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

Although extensive efforts have been made to dampen the thermoacoustic instability,successfully controlling the pressure oscillations in modern gas turbines or aeroengines remains *** influence of the acoustic liner on the longitudinal thermoacoustic mode in a model annular combustor is investigated by large eddy simulation(LES) in this *** result of the self-excited longitudinal thermoacoustic instability without the liner agrees well with the frequency and acoustic analysis of the pressure mode based on experimental *** different bias flow velocities of the liner located downstream of the combustor are then *** results reveal that the existence of the liner influences not only the acoustic field but also the flow *** the bias velocity is large,it leads to intense turbulence-induced fluctuations,and the pressure oscillation is modulated *** shows that the weak coupling between flow and pressure oscillations plays a significant role in the onset of the intermittency of a thermoacoustic *** on the dynamic analysis of the thermoacoustic system with the acoustic liner,this intermittency is caused by the influence of the flow field on the flame-acoustic ***,a low-order modeling method based on Van der Pol(VdP) oscillator with additive stochastic forcing is conducted to reproduce the evolving dynamics of the thermoacoustic *** the numerical cases demonstrated in this work are relatively simpler than those in a practical combustion system,the results are helpful for us to understand the effect of the acoustic liner and show the attractive potential to apply this device to suppress thermoacoustic instability.

关键词： thermoacoustic instability acoustic liner large eddy simulation low-order modeling

Frontogenesis and Frontolysis of a Cold Filament Driven by the Cross-Filament Wind and Wave Fields Simulated by a large eddy simulation

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第3期41卷 509-528页

作者： Guojing LI Dongxiao WANG Changming DONG Jiayi PAN Yeqiang SHU Zhenqiu ZHANG State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Shool of Marine Sciences Nanjing University of Information Science and TechnologyNanjing 210044China School of Geography and Environment Jiangxi Normal UniversityNanchang 330022China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China

The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are *** results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow *** lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.

关键词： cold filament frontogenesis frontolysis large eddy simulation

large eddy simulation of transient transport and entrapment of particle during slab continuous casting

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2022年第2期29卷 247-262页

作者： Yan-bin Yin Jiong-ming Zhang State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing100083China

To investigate the transient transport and entrapment of argon bubbles and inclusions simultaneously during continuous casting,a 3D large eddy simulation model coupling molten steel flow,solidification and particle motion was *** this model,momentum transfer between molten steel and argon bubbles was performed by two-way *** predicted results indicate that argon bubble injection changed the flow pattern of molten steel and the inclusion motion in the liquid ***,the inclusion capture near the solidifying front was *** addition,measurements of bubbles and inclusions in the obtained samples were performed by methods of optical microscope examination and galvanostatic *** results show a favorable agreement between the model predictions and the measured results,which validate the mathematical ***,the predicted results of the inclusion entrapment in the case with argon bubble injection are more compatible with the measurements than those in the case without argon bubble injection.

关键词： large eddy simulation Slab continuous casting Flow Solidification Argon bubble injection Particle motion Particle entrapment

large eddy simulation of the Effects of Plasma Actuation Strength on Film Cooling Efficiency

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2016年第11期18卷 1101-1109页

作者： LI Guozhan CHEN Fu LI Linxi SONG Yanping School of Energy Science and Engineering Harbin Institute of Technology Harbin 150001 China

In this article, numerical investigation of the effects of different plasma actuation strengths on the film cooling flow characteristics has been conducted using large eddy simulation （LES）. For this numerical research, the plasma actuator is placed downstream of the trailing edge of the film cooling hole and a phenomenological model is employed to provide the electric field generated by it, resulting in the body forces. Our results show that as the plasma actuation strength grows larger, under the downward effect of the plasma actuation, the jet trajectory near the cooling hole stays closer to the wall and the recirculation region observably reduces in size. Meanwhile, the momentum injection effect of the plasma actuation also actively alters the distributions of the velocity components downstream of the cooling hole. Consequently, the influence of the plasma actuation strength on the Reynolds stress downstream of the cooling hole is remarkable. Furthermore, the plasma actuation weakens the strength of the kidney shaped vortex and prevents the jet from lifting off the wall. Therefore, with the increase of the strength of the plasma actuation, the coolant core stays closer to the wall and tends to split into two distinct regions. So the centerline film cooling efficiency is enhanced, and it is increased by 55% at most when the plasma actuation strength is 10.

关键词： large eddy simulation plasma actuation strength film cooling flow characteristic

large eddy simulation of vertical turbulent jets under JONSWAP waves

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2011年第2期27卷 189-199页

作者： Jun Lu Ling-Ling Wang Hong-Wu Tang Hui-Chao Dai College of Water Conservancy and Hydro-power Engineering Hohai University 210098 Nanjing China Binhu Water Resource Bureaus 214011 Wuxi China

The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier–Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.

关键词： large eddy simulation Dynamic coherent eddy model σ-coordinate Turbulent jet JONSWAP wave

large eddy simulation of Turbulent Channel Flows over Rough Walls with Stochastic Roughness Height Distributions

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2020年第3期32卷 570-581页

作者： Hao Lu China Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Education Ministry School of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510640China

This paper studies the 3-D turbulent channel flows over rough walls with stochastic roughness height distributions by using the large eddy simulation and the immersed boundary method. The obtained mean and fluctuating velocity profiles for the smooth and rough channel flows agree well with the available numerical and experimental results. The stochastic surface roughness is found to have a more significant influence than the uniform surface roughness on the turbulent velocity statistics and the coherent structures, with the same average roughness height. With a greater variation in the roughness height, the mean velocity and the streamwise fluctuating velocity is decreased and the spanwise velocity and the wall-normal fluctuating velocity are increased. In addition, one observes larger and more profuse quasi-streamwise vortices, hairpin vortices and elongated structures above the crest plane of the roughness array in cases of highly stochastic rough walls. However, the low-speed streaky structures are broken up locally and the ejection and sweep events are depressed by the stochastic roughness below the average roughness height. The results of this study support Townsend’s wall-similarity hypothesis for both stochastic and uniform rough wall turbulences, demonstrating that in both cases the effects of the surface roughness on the turbulent flow are limited to the rough sub-layer.

关键词： large eddy simulation turbulent channel flow rough wall stochastic roughness height

large eddy simulation on the flow characteristics of an argon thermal plasma jet

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2021年第12期23卷 105-116页

作者： Xu ZHOU Xianhui CHEN Taohong YE Minming ZHU School of Engineering Science University of Science and Technology of ChinaHefei 230022People's Republic of China

large eddy simulations based on the CFD software Open FOAM have been used to study the effect of Reynolds number and turbulence intensity on the flow and mixing characteristics of an argon thermal plasma *** analysis was carried out with respect to four aspects:the average flow field,the instantaneous flow field,turbulence statistical characteristics and the *** was shown that for the argon thermal plasma jet with low Reynolds number,increasing the turbulence intensity will increase the turbulent transport mechanism in the mixing layer rather than in the jet axis,leading to the faster development of *** effect of the turbulent transport mechanism increases with increasing Reynolds ***,the characteristics of flow and mixing are not affected by turbulence intensity for high Reynolds number *** was also found that the mean axial velocity and mean temperature in the axis of the turbulent thermal plasma jet satisfy the self-similarity aspects *** addition,decay constant K is 1.25,which is much smaller than that(5.7-6.1)of the turbulent cold gas jet and has nothing to do with the Reynolds number or turbulence intensity in the jet inlet.

关键词： thermal plasma jet mixing layer characteristics Reynolds number turbulence intensity large eddy simulation