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Comparison of ERA5 turbulent fluxes at the air-sea interface with measurements from a wave-following platform
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作者 Said Benjeddou Denis Bourras Christopher Luneau 《Atmospheric and Oceanic Science Letters》 CSCD 2024年第3期32-36,共5页
Turbulent fluxes at the air-sea interface were estimated with data collected in 2011-2020 with a low-profile platform named OCARINA during eight experiments in five regions:2011,2015,and 2016 in the Iroise Sea;2012 in... Turbulent fluxes at the air-sea interface were estimated with data collected in 2011-2020 with a low-profile platform named OCARINA during eight experiments in five regions:2011,2015,and 2016 in the Iroise Sea;2012 in the tropical Atlantic;2014 in the Chilie-Peru upwelling;2017 and 2018 in the Mediterranean Sea,and 2018 and 2020 in Barbados.The observations were carried out with moderate winds(2-10 m s^(-1))and average wave heights of 1.5 m.In this study,the authors used the fluxes calculated by the bulk method using OCARINA-sampled data as the input.These data can validate the fluxes estimated from ERAS reanalysis data.The OCARINA and ERA5 data were taken concomitantly.To do this,the authors established an algorithm to extract the OCARINA data as closely as possible to the reanalysis data in time and position.The measurements of the OCARINA platform can conclude on the relevance of the widely used reanalysis data. 展开更多
关键词 Ocarina ECMWF ERA5 turbulent fluxes Louis formulation
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Analytical solutions of turbulent boundary layer beneath forward-leaning waves
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作者 Yiqin XIE Jifu ZHOU +3 位作者 Xu WANG Jinlong DUAN Yongjun LU Shouqian LI 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第4期695-710,共16页
As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteris... As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteristics of the boundary layer beneath forward-leaning waves accurately,especially for the turbulent boundary layer.In this work,the linearized turbulent boundary layer model with a linear turbulent viscosity coefficient is applied,and the novel expression of the near-bed orbital velocity that has been worked out by the authors for forward-leaning waves of arbitrary forward-leaning degrees is further used to specify the free stream boundary condition of the bottom boundary layer.Then,a variable transformation is found so as to make the equation of the turbulent boundary layer model be solved analytically through a modified Bessel function.Consequently,an explicit analytical solution of the turbulent boundary layer beneath forward-leaning waves is derived by means of variable separation and variable transformation.The analytical solutions of the velocity profile and bottom shear stress of the turbulent boundary layer beneath forward-leaning waves are verified by comparing the present analytical results with typical experimental data available in the previous literature. 展开更多
关键词 forward-leaning wave turbulent boundary layer velocity profile bottom shear stress
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Observing the air-sea turbulent heat flux on the trajectory of tropical storm Danas
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作者 Xuehan XIE Xiangzhou SONG +3 位作者 Marilena OLTMANNS Yangang LI Qifeng QIAN Zexun WEI 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第5期1425-1437,共13页
Tropical cyclones constitute a major risk for coastal communities.To assess their damage potential,accurate predictions of their intensification are needed,which requires a detailed understanding of the evolution of t... Tropical cyclones constitute a major risk for coastal communities.To assess their damage potential,accurate predictions of their intensification are needed,which requires a detailed understanding of the evolution of turbulent heat flux(THF).By combining multiple buoy observations along the south north storm track,we investigated the THF anomalies associated with tropical storm Danas(2019)in the East China Sea(ECS)during its complete life cycle from the intensification stage to the mature stage and finally to its dissipation on land.The storm passage is characterized by strong winds of 10-20 m/s and a sea level pressure below 1000 hPa,resulting in a substantial enhancement of THF.Latent heat(LH)fluxes are most strongly affected by wind speed,with a gradually increasing contribution of humidity along the trajectory.The relative contributions of wind speed and temperature anomalies to sensible heat(SH)depend on the stability of the boundary layer.Under stable conditions,SH variations are driven by wind speed,while under near-neutral conditions,SH variations are driven by temperature.A comparison of the observed THF and associated variables with outputs from the ERA 5 and MERRA 2 reanalysis products reveals that the reanalysis products can reproduce the basic evolution and composition of the observed THF.However,under extreme weather conditions,temperature and humidity variations are poorly captured by ERA 5 and MERRA 2,leading to large LH and SH errors.The differences in the observed and reproduced LH and SH during the passage of Danas amount to 26.1 and 6.6 W/m^(2) for ERA 5,respectively,and to 39.4 and 12.5 W/m^(2) for MERRA 2,respectively.These results demonstrate the need to improve the representation of tropical cyclones in reanalysis products to better predict their intensification process and reduce their damage. 展开更多
关键词 tropical cyclone(TC) air-sea turbulent heat flux(THF) latent heat flux sensible heat flux buoy observation reanalysis product
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The Turbulent Schmidt Number for Transient Contaminant Dispersion in a Large Ventilated Room Using a Realizable k-εModel
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作者 Fei Wang Qinpeng Meng +3 位作者 Jinchi Zhao Xin Wang Yuhong Liu Qianru Zhang 《Fluid Dynamics & Materials Processing》 EI 2024年第4期829-846,共18页
Buildings with large open spaces in which chemicals are handled are often exposed to the risk of explosions.Computational fluid dynamics is a useful and convenient way to investigate contaminant dispersion in such lar... Buildings with large open spaces in which chemicals are handled are often exposed to the risk of explosions.Computational fluid dynamics is a useful and convenient way to investigate contaminant dispersion in such large spaces.The turbulent Schmidt number(Sc_(t))concept has typically been used in this regard,and most studies have adopted a default value.We studied the concentration distribution for sulfur hexafluoride(SF_(6))assuming different emission rates and considering the effect of Sc_(t).Then we examined the same problem for a light gas by assuming hydrogen gas(H_(2))as the contaminant.When SF_(6) was considered as the contaminant gas,a variation in the emission rate completely changed the concentration distribution.When the emission rate was low,the gravitational effect did not take place.For both low and high emission rates,an increase in S_(ct) accelerated the transport rate of SF_(6).In contrast,for H_(2) as the contaminant gas,a larger S_(ct) could induce a decrease in the H_(2) transport rate. 展开更多
关键词 Large space CFD turbulent Schmidt number contaminant dispersion emission rate
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Stochastic Analysis and Modeling of Velocity Observations in Turbulent Flows
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作者 Evangelos Rozos Jorge Leandro Demetris Koutsoyiannis 《Journal of Environmental & Earth Sciences》 CAS 2024年第1期45-56,共12页
Highly turbulent water flows,often encountered near human constructions like bridge piers,spillways,and weirs,display intricate dynamics characterized by the formation of eddies and vortices.These formations,varying i... Highly turbulent water flows,often encountered near human constructions like bridge piers,spillways,and weirs,display intricate dynamics characterized by the formation of eddies and vortices.These formations,varying in sizes and lifespans,significantly influence the distribution of fluid velocities within the flow.Subsequently,the rapid velocity fluctuations in highly turbulent flows lead to elevated shear and normal stress levels.For this reason,to meticulously study these dynamics,more often than not,physical modeling is employed for studying the impact of turbulent flows on the stability and longevity of nearby structures.Despite the effectiveness of physical modeling,various monitoring challenges arise,including flow disruption,the necessity for concurrent gauging at multiple locations,and the duration of measurements.Addressing these challenges,image velocimetry emerges as an ideal method in fluid mechanics,particularly for studying turbulent flows.To account for measurement duration,a probabilistic approach utilizing a probability density function(PDF)is suggested to mitigate uncertainty in estimated average and maximum values.However,it becomes evident that deriving the PDF is not straightforward for all turbulence-induced stresses.In response,this study proposes a novel approach by combining image velocimetry with a stochastic model to provide a generic yet accurate description of flow dynamics in such applications.This integration enables an approach based on the probability of failure,facilitating a more comprehensive analysis of turbulent flows.Such an approach is essential for estimating both short-and long-term stresses on hydraulic constructions under assessment. 展开更多
关键词 Smart modeling turbulent flows Data analysis Stochastic analysis Image velocimetry
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Turbulent Image Restoration in Atmosphere with Cyclopean Processing via Binocular Fusion
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作者 Han Yao Jin-Yan Lin +2 位作者 Li-Bang Chen Yi-Kun Liu Jian-Ying Zhou 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第8期33-38,共6页
The outstanding issue to overcoming atmospheric turbulence on distant imaging is a fundamental interest and technological challenge.We propose a novel scenario and technique to restore the optical image in turbulent e... The outstanding issue to overcoming atmospheric turbulence on distant imaging is a fundamental interest and technological challenge.We propose a novel scenario and technique to restore the optical image in turbulent environmental by referring to Cyclopean image with binocular vision.With human visual intelligence,image distortion resulting from the turbulence is shown to be substantially suppressed.Numerical simulation results taking into account of the atmospheric turbulence,optical image system,image sensors,display and binocular vision perception are presented to demonstrate the robustness of the image restoration,which is compared with a single channel planar optical imaging and sensing.Experiment involving binocular telescope,image recording and the stereo-image display is conducted and good agreement is obtained between the simulation with perceptive experience.A natural extension of the scenario is to enhance the capability of anti-vibration or anti-shaking for general optical imaging with Cyclopean image. 展开更多
关键词 image TURBULENCE SHAKING
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Numerical Simulation of Turbulent Diffusion Flames of a Biogas Enriched with Hydrogen
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作者 Naima Krarraz Amina Sabeur +1 位作者 Khadidja Safer Ahmed Ouadha 《Fluid Dynamics & Materials Processing》 EI 2024年第1期79-96,共18页
Any biogas produced by the anaerobic fermentation of organic materials has the advantage of being an environmentally friendly biofuel.Nevertheless,the relatively low calorific value of such gases makes their effective... Any biogas produced by the anaerobic fermentation of organic materials has the advantage of being an environmentally friendly biofuel.Nevertheless,the relatively low calorific value of such gases makes their effective utilization in practical applications relatively difficult.The present study considers the addition of hydrogen as a potential solution to mitigate this issue.In particular,the properties of turbulent diffusion jet flames and the related pollutant emissions are investigated numerically for different operating pressures.The related numerical simulations are conducted by solving the RANS equations in the frame of the Reynolds Stress Model in combination with the flamelet approach.Radiation effects are also taken into account and the combustion kinetics are described via the GRI-Mech 3.0 reaction model.The considered hydrogen fuel enrichment spans the range from 0%to 50%in terms of volume.Pressure varies between 1 and 10 atm.The results show that both hydrogen addition and pressure increase lead to an improvement in terms of mixing quality and have a significant effect on flame temperature and height.They also reduce CO_(2) emissions but increase NOx production.Prompt NO is shown to be the predominant NO formation mechanism. 展开更多
关键词 BIOGAS HYDROGEN diffusion flame TURBULENCE NO formation route PRESSURE
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Analysis of particle dispersion in a turbulent flow considering particle rotation 被引量:1
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作者 Wenshi Huang Yang Zhang +2 位作者 Yuxin Wu Jingyu Wang Minmin Zhou 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2023年第6期29-39,共11页
Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of n... Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of non-spherical particles considering particle drag correction,lift,and rotation was established.Based on the Eulerian-Lagrangian simulation,the dispersion characteristics of spherical and nonspherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation.The results show that,the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant,especially when Stokes number is large.Moreover,the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail,which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion. 展开更多
关键词 DISPERSION PARTICLE Particle-laden flows Particle rotation turbulent flow
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Observed characteristics of flow,water mass,and turbulent mixing in the Preparis Channel 被引量:1
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作者 Ruijie Ye Feng Zhou +7 位作者 Xiao Ma Dingyong Zeng Feilong Lin Hongliang Li Chenggang Liu Soe Moe Lwin Hlaing Swe Win Soe Pyae Aung 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第2期83-93,共11页
Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea(AS).A set of hydrographic measurements,a microstructure profiler,and a deep mooring were ... Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea(AS).A set of hydrographic measurements,a microstructure profiler,and a deep mooring were used to determine the characteristics of water masses,turbulent mixing,and flows in the Preparis Channel.The unprecedented short-term mooring data reveal that a deep current in the deep narrow passage(below 400 m)of the Preparis Channel flows toward the Bay of Bengal(BoB)with a mean along-stream velocity of 25.26 cm/s at depth of 540 m;above the deep current,there are a relatively weak current flows toward the AS with a mean along-stream velocity of 15.46 cm/s between 500 m and 520 m,and another weak current flows toward the BoB between 430 m and 500 m.Thus,a sandwiched vertical structure of deep currents(below 400 m)is present in the Preparis Channel.The volume transport below 400 m is 0.06 Sv(1 Sv=106 m^(3)/s)from the AS to the BoB.In the upper layer(shallower than 300 m),the sea water of the AS is relatively warmer and fresher than that in the BoB,indicating a strong exchange through the channel.Microstructure profiler observations reveal that the turbulent diffusivity in the upper layer of the Preparis Channel reaches O(10−4 m^(2)/s),one order larger than that in the interior of the BoB and over the continental slope of the northern AS.We speculate that energetic high-mode internal tides in the Preparis Channel contribute to elevated turbulent mixing.In addition,a local“hotspot”of turbidity is identified at the deep mooring site,at depth of about 100 m,which corresponds to the location of elevated turbulent mixing in the Preparis Channel. 展开更多
关键词 deep flow turbulent mixing water mass Preparis Channel
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Artificial neural network-based subgrid-scale models for LES of compressible turbulent channel flow 被引量:1
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作者 Qingjia Meng Zhou Jiang Jianchun Wang 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第1期58-69,共12页
Fully connected neural networks(FCNNs)have been developed for the closure of subgrid-scale(SGS)stress and SGS heat flux in large-eddy simulations of compressible turbulent channel flow.The FCNNbased SGS model trained ... Fully connected neural networks(FCNNs)have been developed for the closure of subgrid-scale(SGS)stress and SGS heat flux in large-eddy simulations of compressible turbulent channel flow.The FCNNbased SGS model trained using data with Mach number Ma=3.0 and Reynolds number Re=3000 was applied to situations with different Mach numbers and Reynolds numbers.The input variables of the neural network model were the filtered velocity gradients and temperature gradients at a single spatial grid point.The a priori test showed that the FCNN model had a correlation coefficient larger than 0.91 and a relative error smaller than 0.43,with much better reconstructions of SGS unclosed terms than the dynamic Smagorinsky model(DSM).In a posteriori test,the behavior of the FCNN model was marginally better than that of the DSM in predicting the mean velocity profiles,mean temperature profiles,turbulent intensities,total Reynolds stress,total Reynolds heat flux,and mean SGS flux of kinetic energy,and outperformed the Smagorinsky model. 展开更多
关键词 Compressible turbulent channel flow Fully connected neural network model Large eddy simulation
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Evaluating Parameterizations for Turbulent Fluxes over the Landfast Sea-Ice Surface in Prydz Bay, Antarctica
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作者 Fangyuan CHENG Qinghua YANG +3 位作者 Changwei LIU Bo HAN Shijie PENG Guanghua HAO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2023年第10期1816-1832,共17页
It is crucial to appropriately determine turbulent fluxes in numerical models.Using data collected in East Antarctica from 8 April to 26 November 2016,this study evaluates parameterization schemes for turbulent fluxes... It is crucial to appropriately determine turbulent fluxes in numerical models.Using data collected in East Antarctica from 8 April to 26 November 2016,this study evaluates parameterization schemes for turbulent fluxes over the landfast seaice surface in five numerical models.The Community Noah Land Surface Model with Multi-Parameterizations Options(Noah_mp)best replicates the turbulent momentum flux,while the Beijing Climate System Model(BCC_CSM)produces the optimum sensible and latent heat fluxes.In particular,two critical issues of parameterization schemes,stability functions and roughness lengths,are investigated.Sensitivity tests indicate that roughness lengths play a decisive role in model performance.Based on the observed turbulent fluxes,roughness lengths over the landfast sea-ice surface are calculated.The results,which can provide a basis for setting up model parameters,reveal that the dynamic roughness length(z0m)increases with the increase of frictional velocity(u*)when u*≤0.4 m s^(−1) and fluctuates around 10^(−3 )m when u*>0.4 m s^(−1);thermal roughness length(z0t)is linearly related to the temperature gradient between air and sea-ice surface(ΔT)with a relation of lg(z0t)=−0.29ΔT−3.86;and the mean water vapor roughness length(z0q)in the specific humidity gradient(Δq)range ofΔq≤−0.6 g kg^(−1) is 10^(−6) m,3.5 times smaller than that in the range ofΔq˃−0.6 g kg^(−1). 展开更多
关键词 turbulent fluxes ANTARCTICA landfast sea-ice surface PARAMETERIZATION EVALUATING numerical models
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Turbulent Kinetic Energy of Flow during Inhale and Exhale to Characterize the Severity of Obstructive Sleep Apnea Patient
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作者 W.M.Faizal C.Y.Khor +4 位作者 Muhammad Nooramin Che Yaakob N.N.N.Ghazali M.Z.Zainon Norliza Binti Ibrahim Roziana Mohd Razi 《Computer Modeling in Engineering & Sciences》 SCIE EI 2023年第7期43-61,共19页
This paper aims to investigate and present the numerical investigation of airflow characteristics using Turbulent Kinetic Energy(TKE)to characterize the upper airway with obstructive sleep apnea(OSA)under inhale and e... This paper aims to investigate and present the numerical investigation of airflow characteristics using Turbulent Kinetic Energy(TKE)to characterize the upper airway with obstructive sleep apnea(OSA)under inhale and exhale breathing conditions.The importance of TKE under both breathing conditions is that it showan accuratemethod in expressing the severity of flow in sleep disorder.Computational fluid dynamics simulate the upper airway’s airflow via steady-state Reynolds-averaged Navier-Stokes(RANS)with k–ωshear stress transport(SST)turbulencemodel.The three-dimensional(3D)airway model is created based on the CT scan images of an actual patient,meshed with 1.29 million elements using Materialise Interactive Medical Image Control System(MIMICS)and ANSYS software,respectively.High TKE were noticed around the region after the necking(smaller cross-sectional area)during the inhale and exhale breathing.The turbulent kinetic energy could be used as a valuablemeasure to identify the severity of OSA.This study is expected to provide a better understanding and clear visualization of the airflow characteristics during the inhale and exhale breathing in the upper airway of patients for medical practitioners in the OSA research field. 展开更多
关键词 Obstructive sleep apnea breathing disorders real patient CFD turbulent kinetic energy
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Evolution of edge turbulent transport induced by L-mode detachment in the HL-2A tokamak
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作者 吴婷 聂林 +17 位作者 余羿 高金明 李俊颜 马会聪 闻杰 柯锐 吴娜 黄治辉 刘亮 郑典麟 弋开阳 高霄雁 王威策 程钧 严龙文 才来中 王占辉 许敏 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第1期10-19,共10页
This paper presents the characteristics of L-mode detachment,together with the behavior of edge turbulent transport and plasma confinement on the HL-2A tokamak.Partially detached and pronounced detached states have be... This paper presents the characteristics of L-mode detachment,together with the behavior of edge turbulent transport and plasma confinement on the HL-2A tokamak.Partially detached and pronounced detached states have been achieved in L-mode plasma.Stored energy was maintained before and after detachment.Edge turbulence and its transport have increased obviously in the partially detached state.In the pronounced detached state,redistribution of the density and temperature profiles due to detachment leads to low amplitude of electron temperature and pressure,as well as very weak edge turbulence and transport.Despite strong plasma radiation in the pronounced detached state,reduced edge turbulent transport contributes to maintaining stored energy in detached L-mode plasma in HL-2A.Different detachment states play an important role in the redistribution of density and temperature profiles,which requires further study. 展开更多
关键词 L-mode detachment turbulent transport CONFINEMENT HL-2A tokamak
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Turbulent boundary layer control with DBD plasma actuators
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作者 李跃强 武斌 +3 位作者 高超 郑海波 王玉帅 严日华 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第4期184-194,共11页
The flat-plate turbulent boundary layer at Reτ=1140 is manipulated using a spanwise array of bidirectional dielectric barrier discharge(DBD)plasma actuators.Based on the features of no moving mechanical parts in the ... The flat-plate turbulent boundary layer at Reτ=1140 is manipulated using a spanwise array of bidirectional dielectric barrier discharge(DBD)plasma actuators.Based on the features of no moving mechanical parts in the DBD plasma control technology and hot-wire anemometer velocity measurements,a novel convenient method of local drag reduction(DR)measurement is proposed by measuring the single-point velocity within the linear region of the viscous sublayer.We analyze the premise of using the method,and the maximum effective measurement range of-73.1%<DR<42.2%is obtained according to the experimental environment in this work.The local drag decreases downstream of the center of two adjacent upper electrodes and increases downstream of the upper electrodes.The magnitude of the local DR increases with increasing voltage and decreases as it moves away from the actuators.For the spanwise position in between,the streamwise distribution of the local DR is very dependent on the voltage.The variable-interval time-average detection results reveal that all bursting intensities are reduced compared to the baseline,and the amount of reduction is comparable to the absolute values of the local DR.Compared with previous results,we infer that the control mechanism is that many meandering streaks are combined together into single stabilized streaks. 展开更多
关键词 turbulent boundary layer control DBD plasma actuators drag reduction measurement
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Simulation Analysis of New Energy Vehicle Engine Cooling System Based on K-E Turbulent Flow Mathematical Model
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作者 Hongyu Mu Yinyan Wang +7 位作者 Chuanlei Yang Hong Teng Xingtian Zhao Hongquan Lu Dechun Wang Shiyang Hao Xiaolong Zhang Yan Jin 《Energy Engineering》 EI 2023年第10期2325-2342,共18页
New energy vehicles have better clean and environmental protection characteristics than traditional fuel vehicles.The new energy engine cooling technology is critical in the design of new energy vehicles.This paper us... New energy vehicles have better clean and environmental protection characteristics than traditional fuel vehicles.The new energy engine cooling technology is critical in the design of new energy vehicles.This paper used oneand three-way joint simulation methods to simulate the refrigeration system of new energy vehicles.Firstly,a k-εturbulent flow model for the cooling pump flow field is established based on the principle of computational fluid dynamics.Then,the CFD commercial fluid analysis software FLUENT is used to simulate the flow field of the cooling pump under different inlet flow conditions.This paper proposes an optimization scheme for new energy vehicle engines’“boiling”phenomenon under high temperatures and long-time climbing conditions.The simulation results show that changing the radiator’s structure and adjusting the thermostat’s parameters can solve the problem of a“boiling pot.”The optimized new energy vehicle engine can maintain a better operating temperature range.The algorithm model can reference each cryogenic system component hardware selection and control strategy in the new energy vehicle’s engine. 展开更多
关键词 New energy vehicle new energy vehicle engine k-ε turbulent flow mathematical model cooling system PID control
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Artificial neural network-based one-equation model for simulation of laminar-turbulent transitional flow 被引量:2
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作者 Lei Wu Bing Cui Zuoli Xiao 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第1期50-57,共8页
A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equa... A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras(SA)-γmodel.By taking SA-γmodel as the benchmark,the present ANN model is trained at two airfoils with various angles of attack,Mach numbers and Reynolds numbers,and tested with unseen airfoils in different flow states.The a posteriori tests manifest that the mean pressure coefficient,skin friction coefficient,size of laminar separation bubble,mean streamwise velocity,Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-γmodel.Furthermore,the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-γmodel. 展开更多
关键词 TRANSITION TURBULENCE Eddy-viscosity model Artificial neural network Intermittency factor
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Turbulent drag reduction by spanwise slot blowing pulsed plasma actuation 被引量:1
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作者 Borui ZHENG Yuanzhong JIN +3 位作者 Minghao YU Yueqiang LI Bin WU Quanlong CHEN 《Plasma Science and Technology》 SCIE EI CAS CSCD 2022年第11期26-36,共11页
This work studies the turbulent drag reduction(TDR)effect of a flat plate model using a spanwise slot blowing pulsed plasma actuator(SBP-PA).Wind tunnel experiments are carried out under a Reynolds number of 1.445... This work studies the turbulent drag reduction(TDR)effect of a flat plate model using a spanwise slot blowing pulsed plasma actuator(SBP-PA).Wind tunnel experiments are carried out under a Reynolds number of 1.445×10^(4).Using a hot-wire anemometer and an electrical data acquisition system,the influences of millisecond pulsed plasma actuation with different burst frequencies and duty cycles on the microscale coherent structures near the wall of the turbulent boundary layer(TBL)are studied.The experimental results show that the SBP-PA can effectively reduce the frictional drag of the TBL.When the duty cycle exceeds 30%,the TDR rate is greater than 11%,and the optimal drag reduction rate of 13.69%is obtained at a duty cycle of 50%.Furthermore,optimizing the electrical parameters reveals that increasing the burst frequency significantly reduces the velocity distribution in the logarithmic region of the TBL.When the normalized burst frequency reaches f+=2πf_(p)d/U_(∞)=7.196,the optimal TDR effectiveness is 16.97%,indicating a resonance phenomenon between the pulsed plasma actuation and the microscale coherent structures near the wall.Therefore,reasonably selecting the electrical parameters of the plasma actuator is expected to significantly improve the TDR effect. 展开更多
关键词 turbulent boundary layer control plasma flow control HOT-WIRE turbulent frictional drag turbulent drag reduction
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Different Turbulent Regimes and Vertical Turbulence Structures of the Urban Nocturnal Stable Boundary Layer
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作者 Yu SHI Qingcun ZENG +4 位作者 Fei HU Weichen DING Zhe ZHANG Kang ZHANG Lei LIU 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2023年第6期1089-1103,共15页
Turbulence in the nocturnal boundary layer(NBL)is still not well characterized,especially over complex underlying surfaces.Herein,gradient tower data and eddy covariance data collected by the Beijing 325-m tower were ... Turbulence in the nocturnal boundary layer(NBL)is still not well characterized,especially over complex underlying surfaces.Herein,gradient tower data and eddy covariance data collected by the Beijing 325-m tower were used to better understand the differentiating characteristics of turbulence regimes and vertical turbulence structure of urban the NBL.As for heights above the urban canopy layer(UCL),the relationship between turbulence velocity scale(VTKE)and wind speed(V)was consistent with the“HOckey-Stick”(HOST)theory proposed for a relatively flat area.Four regimes have been identified according to urban nocturnal stable boundary layer.Regime 1 occurs where local shear plays a leading role for weak turbulence under the constraint that the wind speed V<VT(threshold wind speed).Regime 2 is determined by the existence of strong turbulence that occurs when V>VT and is mainly driven by bulk shear.Regime 3 is identified by the existence of moderate turbulence when upside-down turbulence sporadic bursts occur in the presence of otherwise weak turbulence.Regime 4 is identified as buoyancy turbulence,when V>VT,and the turbulence regime is affected by a combination of local wind shear,bulk shear and buoyancy turbulence.The turbulence activities demonstrated a weak thermal stratification dependency in regime 1,for which within the UCL,the turbulence intensity was strongly affected by local wind shear when V<VT.This study further showed typical examples of different stable boundary layers and the variations between turbulence regimes by analyzing the evolution of wind vectors.Partly because of the influence of large-scale motions,the power spectral density of vertical velocity for upsidedown structure showed an increase at low frequencies.The upside-down structures were also characterized by the highest frequency of the stable stratifications in the higher layer. 展开更多
关键词 urban canopy layer stable boundary layer upside-down TURBULENCE vertical structure
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NUMERICAL SIMULATION AND ANALYSIS OF HORSESHOE-SHAPED VORTEX IN NEAR-WALL REGION OF TURBULENT BOUNDARY LAYER 被引量:5
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作者 史万里 葛宁 +1 位作者 陈林 唐登斌 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2011年第1期48-56,共9页
The low-Reynolds-number full developed turbulent flow in channels is simulated using large eddy simulation(LES)method with the preconditioned algorithm and the dynamic subgrid-scale model,with a given disturbance in... The low-Reynolds-number full developed turbulent flow in channels is simulated using large eddy simulation(LES)method with the preconditioned algorithm and the dynamic subgrid-scale model,with a given disturbance in inlet boundary,after a short development section.The inlet Reynolds number based on momentum thickness is 670.The computed results show good agreement with direct numerical simulation(DNS),which include root mean square fluctuated velocity distribution and average velocity distribution.It is also found that the staggered phenomenon of the coherent structures is caused by sub-harmonic.The results clearly show the formation and evolution of horseshoe vortex in the turbulent boundary layer,including horseshoe vortex structure with a pair of streamwise vortexes and one-side leg of horseshoe vortex.Based on the results,the development of the horseshoe-shaped coherent structures is analyzed in turbulent boundary layer. 展开更多
关键词 large eddy simulation(LES) horseshoe-shaped vortex turbulent boundary layer coherent structures preconditioned algorithm
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Heat and Mass Transfers in a Two-Phase Stratified Turbulent Fluid Flow in a Geothermal Pipe with Chemical Reaction
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作者 Eric M. Nyariki Mathew N. Kinyanjui Jeconia O. Abonyo 《Journal of Applied Mathematics and Physics》 2023年第2期484-513,共30页
This research focused on the study of heat and mass transfers in a two-phase stratified turbulent fluid flow in a geothermal pipe with chemical reaction. The derived non-linear partial differential equations governing... This research focused on the study of heat and mass transfers in a two-phase stratified turbulent fluid flow in a geothermal pipe with chemical reaction. The derived non-linear partial differential equations governing the flow were solved using the Finite Difference Method. The effects of various physical parameters on the concentration, skin friction, heat, and mass transfers have been determined. Analysis of the results obtained indicated that the coefficient of skin friction decreased with an increase in Reynolds number and solutal Grasholf number, the rate of heat transfer increased with an increase in Eckert number, Prandtl number, and angle of inclination, and the rate of mass transfer increased with increase in Reynolds number, Chemical reaction parameter and angle of inclination. The findings would be useful to engineers in designing and maintaining geothermal pipelines more effectively. 展开更多
关键词 TWO-PHASE Turbulence Non-Newtonian INCLINATION Heat Transfer Mass Transfer STRATIFIED
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