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The Probability Density Function Related to Shallow Cumulus Entrainment Rate and Its Influencing Factors in a large-eddy simulation

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Advances in Atmospheric Sciences 2024年第1期41卷 173-187页

作者： Lei ZHU Chunsong LU Xiaoqi XU Xin HE Junjun LI Shi LUO Yuan WANG Fan WANG Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)and Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science and TechnologyNanjing 210044China Nanjing Joint Institute for Atmospheric Sciences Nanjing 210019China College of Aviation Meteorology Civil Aviation Flight University of ChinaGuanghan 618307China Collaborative Innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China Department of Geography Hong Kong Baptist UniversityHong Kong SAR 999077China

The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus *** obtaining the entrainment rate(λ)is particularly important for its parameterization within the overall cumulus parameterization *** this study,an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculateλof cumulus clouds in a large-eddy *** results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method,becauseλ,as calculated from the improved method,falls within the range ofλvalues obtained from the traditional method using different conserved *** probability density functions ofλfor all data,different times,and different heights can be well-fitted by a log-normal distribution,which supports the assumed stochastic entrainment process in previous *** analysis demonstrate that the relationship betweenλand the vertical velocity is better than other thermodynamic/dynamical properties;thus,the vertical velocity is recommended as the primary influencing factor for the parameterization ofλin the *** results of this study enhance the theoretical understanding ofλand its influencing factors and shed new light on the development ofλparameterization.

关键词： large-eddy simulation cumulus clouds entrainment rate probability density functions spatial and temporal distribution

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Numerical modeling of current-induced scour around multi-wall foundation using large-eddy simulation

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Frontiers of Structural and Civil Engineering 2023年第4期17卷 546-565页

作者： Jiujiang WU Lingjuan WANG Qiangong CHENG Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province Southwest University of Science and TechnologyMianyang 621010China Department of Civil and Environmental Engineering Western UniversityLondonON N6A 5B9Canada Office of International Students Education Southwest University of Science and TechnologyMianyang 621010China Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu 610031China

Scouring is one of the primary triggers of failure for bridges across rivers or ***,research concerning the scour mechanism of multi-wall foundations(MWFs)remains scarce,hindering the further application of *** this study,for the first time,the scouring effect caused by unidirectional flow around MWFs was examined numerically using FLOW-3D involving a large-eddy ***,the applicability of the scouring model and input parameters was validated using a case study based on published measured ***,the scouring effects of four MWFs with different wall arrangements and inflow angles,including the flow field analysis and scour pit and depth,were investigated *** was found that the maximum scour depth of MWFs with an inflow angle of 0°was smaller than that of those with an inflow angle of 45°,regardless of the wall ***,changing the inflow angle significantly affects the scour characteristics of MWFs arranged in *** practical engineering,MWFs arranged in parallel are preferred considering the need for scouring ***,a comparative analysis should be performed to consider comprehensively whether to adopt the form of a round wall arrangement when the inflow angle is not 0°or the inflow direction is changeable.

关键词： multi-wall foundation current-induced scour bridge foundation large-eddy simulation numerical analysis

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Dynamic nonlinear algebraic models with scale-similarity dynamic procedure for large-eddy simulation of turbulence

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Advances in Aerodynamics 2022年第1期4卷 304-326页

作者： Zelong Yuan Yunpeng Wang Chenyue Xie Jianchun Wang Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen518055China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou511458China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Southern University of Science and TechnologyShenzhen518055China Department of Ocean Science The Hong Kong University of Science and TechnologyHong Kong999077China

A dynamic nonlinear algebraic model with scale-similarity dynamic procedure(DNAM-SSD)is proposed for subgrid-scale(SGS)stress in large-eddy simulation of *** model coefficients of the DNAM-SSD model are adaptively calculated through the scale-similarity relation,which greatly simplifies the conventional Germano-identity based dynamic procedure(GID).The a priori study shows that the DNAM-SSD model predicts the SGS stress considerably better than the conventional velocity gradient model(VGM),dynamic Smagorinsky model(DSM),dynamic mixed model(DMM)and DNAM-GID model at a variety of filter widths ranging from inertial to viscous *** correlation coefficients of the SGS stress predicted by the DNAM-SSD model can be larger than 95%with the relative errors lower than 30%.In the a posteriori testings of LES,the DNAM-SSD model outperforms the implicit LES(ILES),DSM,DMM and DNAM-GID models without increasing computational costs,which only takes up half the time of the DNAM-GID *** DNAM-SSD model accurately predicts plenty of turbulent statistics and instantaneous spatial structures in reasonable agreement with the filtered DNS *** results indicate that the current DNAM-SSD model is attractive for the development of highly accurate SGS models for LES of turbulence.

关键词： Subgrid-scale model Nonlinear algebraic model large-eddy simulation Incompressible turbulence

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large-eddy simulation of Fluid Flow and Heat Transfer in a Mixing Tee Junction

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Chinese Journal of Mechanical Engineering 2012年第6期25卷 1144-1150页

作者： LU Tao WANG Yongwei WANG Kuisheng School of Mechanical and Electrical Engineering Beijing University of Chemical TechnologyBeijing 100029China

The temperature fluctuation caused by thermal striping phenomena of hot and cold fluids mixing results in cyclical thermal stress fatigue failure of the pipe wall. Mean temperature difference between hot and cold fluids was often used as thermal load in previous analysis of thermal fatigue failure, thereby the influences of the amplitude and frequency of temperature fluctuation on thermal fatigue failure were neglected. Based on the mechanism of flow and heat transfer which induces thermal fatigue, the turbulent mixing of hot and cold water in a tee junction is simulated with FLUENT platform by using the large-eddy simulation（LES） turbulent flow model with the sub-grid scale（SGS） model of Smagorinsky-Lilly（SL） to capture the amplitude and frequency of temperature fluctuation. In a simulation case, hot water with temperature of 343.48 K and velocity of 0.15 m/s enters the horizontal main duct with the side length of 100 mm, while cold water with temperature of 296.78 K and velocity of 0.3 m/s enters the vertical branch duct with the side length of 50 mm. The numerical results show that the mean and fluctuating temperatures are in good agreement with the previous experimental data, which describes numerical simulation with high reliability and accuracy; the power spectrum density（PSD） on top wall is higher than that on bottom wall（as the frequency less than 1 Hz）, while the PSD on bottom wall is relatively higher than that on top wall （as the frequency of 1-10Hz）. The temperature fluctuations in full mixing region of the tee junction can be accurately captured by LES and can provide the theoretical basis for the thermal stress and thermal fatigue analyses.

关键词： large-eddy simulation flow heat transfer tee junction

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large-eddy simulation of shock-wave/turbulent boundary layer interaction with and without Spark Jet control

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Chinese Journal of Aeronautics 2016年第3期29卷 617-629页

作者： Yang Guang Yao Yufeng Fang Jian Gan Tian Li Qiushi Lu Lipeng National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power EngineeringBeihang University Beijing 100083China Faculty.of Environment and Technology University of the West of EnglandBristol BSI6 1Q YUnited Kingdom Computer Scienceand Engineering Department Science&Technology Facilities Council(STFC)Daresbury LaboratoryWarrington WA4 4ADUK

The efficiency and mechanism of an active control device ＂＇Spark Jet＂ and its application in shock-induced separation control are studied using large-eddy simulation in this paper. The base flow is the interaction of an oblique shock-wave generated by 8° wedge and a spatially-developing Ma = 2.3 turbulent boundary layer. The Reynolds number based on the incoming flow property and the boundary layer displacement thickness at the impinging point without shock-wave is 20000. The detailed numerical approaches were presented. The inflow turbulence was generated using the digital filter method to avoid artificial temporal or streamwise periodicity. The , merical results including velocity profile, Reynolds stress profile, skin friction, and wall pressure were sys- tematically validated against the available wind tunnel particle image velocimetry （PIV） measure- ments of the same flow condition. Further study on the control of flow separation due to the strong shock-viscous interaction using an active control actuator ＂＇Spark Jet＇＂ was conducted. The single-pulsed characteristic of the device was obtained and compared with the experiment. Both instantaneous and time-averaged flow fields have shown that the jet flow issuing from the actuator cavity enhances the flow mixing inside the boundary layer, making the boundary layer more resis- tant to flow separation. Skin friction coefficient distribution shows that the separation bubble length is reduced by about 35% with control exerted.

关键词： large-eddy simulation Shock-wave:Turbulent boundary layer Interaction Spark Jet control

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large-eddy simulation of circular cylinder flow at subcritical Reynolds number:Turbulent wake and sound radiation

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Acta Mechanica Sinica 2016年第1期32卷 1-11页

作者： Li Guo Xing Zhang Guowei He China Academy of Aerospace Aerodynamics Beijing 100074China State Key Laboratory of Non-linear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China

The flows past a number 3900 are simulated circular cylinder at Reynolds using large-eddy simulation （LES） and the far-field sound is calculated from the LES results. A low dissipation energy-conserving finite volume scheme is used to discretize the incompressible Navier- Stokes equations. The dynamic global coefficient version of the Vreman＇s subgrid scale （SGS） model is used to com- pute the sub-grid stresses. Curie＇s integral of Lighthill＇s acoustic analogy is used to extract the sound radiated from the cylinder. The profiles of mean velocity and turbulent fluctua- tions obtained are consistent with the previous experimental and computational results. The sound radiation at far field exhibits the characteristic of a dipole and directivity. The sound spectra display the -5/3 power law. It is shown that Vreman＇s SGS model in company with dynamic procedure is suitable for LES of turbulence generated noise.

关键词： Flows past circular cylinder Aerodynamicnoise large-eddy simulation Unstructured grid Acousticanalogy

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large-eddy simulation and experimental study on the turbulent wake flow characteristics of a two-bladed wind turbine

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Science China(Technological Sciences) 2017年第12期60卷 1861-1869页

作者： LUO Kun YUAN RenYu DONG XueQing WANG JianWen ZHANG SanXia FAN JianRen NI MingJiang CEN KeFa State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China School of Energy and Power Engineering Inner Mongolia University of Technology Hohhot 010051 China Key Laboratory of Wind and Solar Power Energy Utilization Technology Ministry of Education and Inner Mongolia Construction Hohhot 010051 China

large-eddy simulation(LES) with fully resolved rotor method(FRM) is applied to explore the turbulent wake flow characteristics and vortex evolution laws of a two-bladed horizontal-axis wind turbine. Relevant wind tunnel experiments have been done based on time resolved particle image velocimetry(TRPIV) technique. The simulation results are validated by the experimental data and they are in good agreement. The axial average velocity, turbulent kinetic energy, shear Reynolds stress, and vortex structure of the wind turbine wake are analyzed based on the comparison of LES results and experimental data. It is observed that the wake diameter of wind turbine enlarges with the increase of tip speed ratio(TSR). Turbulent kinetic energy meets its minimum value when x/R=2.0. Shear Reynolds stress appears a positive peak in the near wake when x/R<2.0, and the value of shear Reynolds stress decreases along the axial direction. The blade tip vortex dissipates more quickly than the central vortex in the wind turbine wake, and the gradient of the relationship curve between the blade tip vortex core position and the vortex age decreases as the TSR increases. With the increase of TSR, the thrust coefficient increases, and the power coefficient increases first and then *** present work proves that LES with FRM could calculate wind turbine turbulent wake flow with a high accuracy.

关键词： large-eddy simulation two-bladed wind turbine time resolved particle image velocimetry tip speed ratio turbulent kinetic energy shear Reynolds stress

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large-eddy simulation of fluid mixing in tee with sintered porous medium

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Applied Mathematics and Mechanics(English Edition) 2012年第7期33卷 911-922页

作者：王永伟卢涛姜培学程鹏飞王奎生 School of Mechanical and Electrical Engineering Beijing University of Chemical Technology Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Thermal EngineeringTsinghua University

Mixing processes of hot and cold fluids in a tee with and without sin- tered copper spheres are simulated by FLUENT using the large-eddy simulation （LES） turbulent flow model and the sub-grid scale （SGS） Smagorinsky-Lilly （SL） model with buoyancy. Comparisons of numerical results of the two cases with and without sintered copper spheres show that the porous medium significantly reduces velocity and temper- ature fluctuations because the porous medium can effectively restrict the fluid flow and enhance heat transfer. The porous medium obviously increases the pressure drop in the main duct. The porous medium reduces the power spectrum density （PSD） of tempera- ture fluctuations in the frequency range from 1 Hz to 10 Hz.

关键词： large-eddy simulation mixing tee sintered porous medium

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large-eddy simulation of wall-bounded turbulent flow with high-order discrete unified gas-kinetic scheme

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Advances in Aerodynamics 2020年第1期2卷 528-554页

作者： Rui Zhang Chengwen Zhong Sha Liu Congshan Zhuo School of Aeronautics Northwestern Polytechnical University127 West Youyi Road710072Xi’anPeople’s Republic of China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University127 West Youyi Road710072Xi’anPeople’s Republic of China

In this paper,we introduce the discrete Maxwellian equilibrium distribution function for incompressible flow and force term into the two-stage third-order Discrete Unified Gas-Kinetic Scheme(DUGKS)for simulating low-speed turbulent *** Wall-Adapting Local eddy-viscosity(WALE)and Vreman sub-grid models for large-eddy simulations(LES)of turbulent flows are coupled within the present ***,the implicit LES are also presented to verify the effect of LES models.A parallel implementation strategy for the present framework is developed,and three canonical wall-bounded turbulent flow cases are investigated,including the fully developed turbulent channel flow at a friction Reynolds number(Re)about 180,the turbulent plane Couette flow at a friction Re number about 93 and lid-driven cubical cavity flow at a Re number of *** turbulence statistics,including mean velocity,the *** velocity,Reynolds stress,*** computed by the present *** predictions match precisely with each other,and they are both in reasonable agreement with the benchmark data of ***,the predicted flow physics of three-dimensional lid-driven cavity flow are consistent with the description from abundant *** present numerical results verify that the present two-stage third-order DUGKS-based LES method is capable for simulating inhomogeneous wall-bounded turbulent flows and getting reliable results with relatively coarse grids.

关键词： large-eddy simulation Wall-bounded turbulent flow DUGKS High order scheme

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Scaling law of resolved-scale isotropic turbulence and its application in large-eddy simulation

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Acta Mechanica Sinica 2014年第3期30卷 339-350页

作者： Le Fang Bo Li Li-Peng Lu cole Centrale de Pe'kin Beihang University The State Key Laboratory of Nonlinear Mechanics Chinese Academy of Science Laboratoire de M canique des Fluides et d’Acoustique Universit de Lyoncole centrale de Lyon69134 EcullyFrance School of Energy and Power Engineering Beihang University

eddy-damping quasinormal Markovian （EDQNM） theory is employed to calculate the resolved-scale spectrum and transfer spectrum, based on which we investigate the resolved-scale scaling law. Results show that the scaling law of the resolved-scale turbulence, which is affected by several factors, is far from that of the full-scale turbulence and should be corrected. These results are then applied to an existing subgrid model to improve its performance. A series of simulations are performed to verify the necessity of a fixed scaling law in the subgrid modeling.

关键词： Scaling law large-eddy simulation CZZSmodel

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