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An Analysis of the Turbulent Structure in the Unstable Surface Layer nearby a Shelter Belt
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作者 曾宗泳 马成胜 +1 位作者 刘晓春 凌蕙琴 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 1989年第4期493-500,共8页
An analysis was performed of the turbulent data obtained from Yucheng experimental station in the Shandong Province in 1984. [t is shown that at variant wind speed, the spectra of streamwise velocity remain similar an... An analysis was performed of the turbulent data obtained from Yucheng experimental station in the Shandong Province in 1984. [t is shown that at variant wind speed, the spectra of streamwise velocity remain similar and the intensity of wind fluctuations is proportional to wind speed in the downwind area of shelter belt. Therefore, we may decide the similarity of wind fluctuations by a speed scale and a length scale which is not correlated with stability, σu /V0 = F(X / H). The -5/3 power range of temperature spectra extends to lower frequency. The variation of ratio σ0 /T. with stability becomes σ0 / T . = C(X / H)( - Z / L)-1/3 . There is not such an extension of -5 / 3 power range in the humidity spectra. 展开更多
关键词 In An Analysis of the turbulent structure in the Unstable Surface Layer nearby a Shelter Belt
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EFFECT OF COOLED BOUNDARY ON THE TURBULENT STRUCTURE 被引量:1
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作者 Li Guo xiang, Mao Hua yong, Li Na School of Energy and Power Engineering, Shandong University, Jinan 250061, China, 《Journal of Hydrodynamics》 SCIE EI CSCD 2003年第5期54-59,共6页
The flow field in the cooled channel of a heat exchanger was measured usingthe X-type film probes of Hot Wire/Firm Anemotheter, and the turbulent mechanism was discussed. Itis concluded that the airflow is cooled in t... The flow field in the cooled channel of a heat exchanger was measured usingthe X-type film probes of Hot Wire/Firm Anemotheter, and the turbulent mechanism was discussed. Itis concluded that the airflow is cooled in the flow process, the distribution of the turbulentintensity is relatively convergent near the centcrline and the boundary, the constriction actionproduced due to heat release at the foot of the fins causes u to decrease and w to increase near theroot downstream. It is concluded that the turbulent flow with cooled boundary results from thebalance of production, dissipation and intermittency caused by constriction action. 展开更多
关键词 heat exchanger COOLING turbulent structure
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ML and CFD Simulation of Flow Structure around Tandem Bridge Piers in Pressurized Flow
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作者 Aliasghar Azma Ramin Kiyanfar +4 位作者 Yakun Liu Masoumeh Azma Di Zhang Ze Cao Zhuoyue Li 《Computers, Materials & Continua》 SCIE EI 2023年第4期1711-1733,共23页
Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notab... Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively. 展开更多
关键词 Bridge pier scour process deck width machine learning turbulent structure
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VISUALIZATION OF FLOW STRUCTURES IN A TURBULENT BOUNDARY LAYER USING A NEW TECHNIQUE 被引量:1
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作者 Shen Gongxin Lian Qixiang +2 位作者 Huang Zheng Ma Guangyun Yuan Youming Fluid Mechanic Institute, BUAA 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1989年第4期376-382,共7页
In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that ... In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer. 展开更多
关键词 structures of turbulent boundary layer high/low speed streaks interface strings hairpin or horseshoe-like vortices flow visualization Hydrogen bubble time line laser light sheet.
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The nature of near-wall convection velocity in turbulent channel flow 被引量:2
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作者 Yuhui Cao Jun Chen Zhensu She 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2008年第5期587-590,共4页
A novel notion of turbulent structure the local cascade structure-is introduced to study the convection phenomenon in a turbulent channel flow. A space-time cross-correlation method is used to calculate the convection... A novel notion of turbulent structure the local cascade structure-is introduced to study the convection phenomenon in a turbulent channel flow. A space-time cross-correlation method is used to calculate the convection velocity. It is found that there are two characteristic convection speeds near the wall, one associated with small-scale streaks of a lower speed and another with streamwise vortices and hairpin vortices of a higher speed. The new concept of turbulent structure is powerful to illustrate the dominant role of coherent structures in the near-wall convection, and to reveal also the nature of the convection-the propagation of patterns of velocity fluctuations-which is scale-dependent. 展开更多
关键词 turbulent structure CASCADE structure classification CONVECTION Channel flow
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Numerical study of the near-wall vortical structures in particle-laden turbulent flow by a new vortex identification method-Liutex
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作者 Farid Rousta Goodarz Ahmadi +1 位作者 Bamdad Lessani Chaoqun Liu 《Journal of Hydrodynamics》 SCIE EI CSCD 2024年第1期53-60,共8页
This study investigates turbulent particle-laden channel flows using direct numerical simulations employing the Eulerian-Lagrangian method.A two-way coupling approach is adopted to explore the mutual interaction betwe... This study investigates turbulent particle-laden channel flows using direct numerical simulations employing the Eulerian-Lagrangian method.A two-way coupling approach is adopted to explore the mutual interaction between particles and fluid flow.The considered cases include flow with particle Stokes number varying from St=2 up to St=100 while maintaining a constant Reynolds number of Reτ=180 across all cases.A novel vortex identification method,Liutex(Rortex),is employed to assess its efficacy in capturing near-wall turbulent coherent structures and their interactions with particles.The Liutex method provides valuable information on vortex strength and vectors at each location,enabling a detailed examination of the complex interaction between fluid and particulate phases.As widely acknowledged,the interplay between clockwise and counterclockwise vortices in the near-wall region gives rise to low-speed streaks along the wall.These low-speed streaks serve as preferential zones for particle concentration,depending upon the particle Stokes number.It is shown that the Liutex method can capture these vortices and identify the location of low-speed streaks.Additionally,it is observed that the particle Stokes number(size)significantly affects both the strength of these vortices and the streaky structure exhibited by particles.Furthermore,a quantitative analysis of particle behavior in the near-wall region and the formation of elongated particle lines was carried out.This involved examining the average fluid streamwise velocity fluctuations at particle locations,average particle concentration,and the normal velocity of particles for each set of particle Stokes numbers.The investigation reveals the intricate interplay between particles and near-wall structures and the significant influence of particles Stokes number.This study contributes to a deeper understanding of turbulent particle-laden channel flow dynamics. 展开更多
关键词 turbulent channel flow particle-laden flow direct numerical simulation(DNS) Eulerian-Lagrangian vortex identification turbulence coherent structures Liutex
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Orthogonal wavelet analysis of counter gradient transport phenomena in turbulent asymmetric channel flow 被引量:2
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作者 JianboJiang XiangQiu ZhimingLu YuluLiu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2005年第2期133-141,共9页
In this paper four families of orthogonal wavelets are applied to analyze the turbulent counter gradient transport phenomena in fully developed asymmetric channel flows. The results show that: (1) In the instance of c... In this paper four families of orthogonal wavelets are applied to analyze the turbulent counter gradient transport phenomena in fully developed asymmetric channel flows. The results show that: (1) In the instance of counter gradient transport, the principal scale of the coherent structure is responsible for the strong local counter gradient transport; (2) Counter gradient transport phenomena have a strong effect on the intermittency of turbulence; (3) Non-Gaussian part of the principal coherent structure is essential for counter gradient transport phenomena. 展开更多
关键词 turbulent counter gradient transport (CGT) Wavelet analysis Turbulence structure
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Corrections to the scaling of the second-order structure function in isotropic turbulence 被引量:6
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作者 Le Fang Wouter J. T. Bos +2 位作者 Xiaozhou Zhou Liang Shao Jean-Pierre Bertoglio 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2010年第2期151-157,共7页
The approach of Obukhov assuming a constant skewness was used to obtain analytical corrections to the scaling of the second order structure function, starting from Kolmogorov's 4/5 law. These corrections can be used ... The approach of Obukhov assuming a constant skewness was used to obtain analytical corrections to the scaling of the second order structure function, starting from Kolmogorov's 4/5 law. These corrections can be used in model applications in which explicit expressions, rather than numerical solutions are needed. The comparison with an interpolation formula proposed by Batchelor, showed that the latter gives surprisingly precise results. The modification of the same method to obtain analytical corrections to the scaling law, taking into account the possible corrections induced by intermittency, is also proposed. 展开更多
关键词 Scaling law · structure function ·Isotropic turbulence
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A study on coherent structures and drag-reduction in the wall turbulence with polymer additives by TRPIV 被引量:4
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作者 Xin-Lei Guan Shi-Yong Yao Nan Jiang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2013年第4期485-493,共9页
An experimental measurement was performed us- ing time-resolved particle image velocimetry (TRPIV) to in- vestigate the spatial topological character of coherent struc- tures in wall-bounded turbulence of polymer ad... An experimental measurement was performed us- ing time-resolved particle image velocimetry (TRPIV) to in- vestigate the spatial topological character of coherent struc- tures in wall-bounded turbulence of polymer additive solu- tion. The fully developed near-wall turbulent flow fields with and without polymer additives at the same Reynolds number were measured by TRPIV in a water channel. The compar- isons of turbulent statistics confirm that due to viscoelastic structure of long-chain polymers, the wall-normal velocity fluctuation and Reynolds shear stress in the near-wall region are suppressed significantly. Furthermore, it is noted that such a behavior of polymers is closely related to the decease of the motion of the second and forth quadrants, i.e., the ejection and sweep events, in the near-wall region. The spa- tial topological mode of coherent structures during bursts has been extracted by the new mu-level criteria based on locally averaged velocity structure function. Although the general shapes of coherent structures are unchanged by polymer additives, the fluctuating velocity, velocity gradient, velocity strain rate and vorticity of coherent structures during burst events are suppressed in the polymer additive solution com- pared with that in water. The results show that due to the polymer additives the occurrence and intensity of coherent structures are suppressed, leading to drag reduction. 展开更多
关键词 Time-resolved particle image velocimetry ~ Wall-bounded turbulence ~ Coherent structures ~ Polymer addi-tives ~ Drag reduction
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Identification, characterization and evolution of non-local quasi-Lagrangian structures in turbulence 被引量:2
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作者 Yue Yang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第3期351-361,共11页
The recent progress on non-local Lagrangian and quasi-Lagrangian structures in turbulence is reviewed.The quasi-Lagrangian structures, e.g., vortex surfaces in viscous flow, gas-liquid interfaces in multi-phase flow, ... The recent progress on non-local Lagrangian and quasi-Lagrangian structures in turbulence is reviewed.The quasi-Lagrangian structures, e.g., vortex surfaces in viscous flow, gas-liquid interfaces in multi-phase flow, and flame fronts in premixed combustion, can show essential Lagrangian following properties, but they are able to have topological changes in the temporal evolution. In addition,they can represent or influence the turbulent flow field. The challenges for the investigation of the non-local structures include their identification, characterization, and evolution.The improving understanding of the quasi-Lagrangian structures is expected to be helpful to elucidate crucial dynamics and develop structure-based predictive models in turbulence. 展开更多
关键词 Turbulence Lagrangian study Coherent structure Multi-scale analysis Vortex dynamics
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Tomographic PIV investigation on coherent vortex structures over shark-skin-inspired drag-reducing riblets 被引量:8
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作者 Shao-Qiong Yang Shan Li +2 位作者 Hai-Ping Tian Qing-Yi Wang Nan Jiang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第2期284-294,共11页
Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-insp... Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer(TBL) is investigated.This is done by means of tomographic particle image velocimetry(TPIV) measurements in channel fl ws over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 190.The turbulent fl ws over drag-reducing riblets are verifie by a planar time-resolved particle image velocimetry(TRPIV) system initially,and then the TPIV measurements are performed.Two-dimensional(2D) experimental results with a dragreduction rate of around 4.81% are clearly visible over triangle riblets with a peak-to-peak spacing s+of 14,indicating from the drag-reducing performance that the buffer layer within the TBL has thickened;the logarithmic law region has shifted upward and the Reynolds shear stress decreased.A comparison of the spatial topological distributions of the spanwise vorticity of coherent vortex structures extracted at different wall-normal heights through the improved quadrant splitting method shows that riblets weaken the amplitudesof the spanwise vorticity when ejection(Q2) and sweep(Q4) events occur at the near wall,having the greatest effect on Q4 events in particular.The so-called quadrupole statistical model for coherent structures in the whole TBL is verified Meanwhile,their spatial conditional-averaged topological shapes and the spatial scales of quadrupole coherent vortex structures as a whole in the overlying turbulent fl w over riblets are changed,suggesting that the riblets dampen the momentum and energy exchange between the regions of near-wall and outer portion of the TBL by depressing the bursting events(Q2 and Q4),thereby reducing the skin friction drag. 展开更多
关键词 turbulent boundary layer(TBL) Coherent vortex structure Flow control Drag reduction Shark-skininspired riblet Tomographic particle image velocimetry(TPIV)
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Backscattering from small-scale breaking wave turbulence structure generated by FLUENT
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作者 罗根 张民 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第12期159-165,共7页
A breaking wave can exert a great influence on the electromagnetic(EM) scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid ... A breaking wave can exert a great influence on the electromagnetic(EM) scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid dynamics(CFD)software FLUENT, and the backscattering radar cross section(RCS) of the turbulence structure after breaking is calculated with the method of moments. The scattering results can reflect the turbulent intensities of the wave profiles and can indicate high polarization ratios at moderate incident angles, which should be attributed to the incoherent backscatter from surface disturbance of turbulence structure. Compared with the wave profile before breaking, the turbulence structure has no obvious geometrical characteristic of a plunging breaker, and no sea spikes are present at large incident angles either.In summary, the study of EM scattering from turbulence structure can provide a basis to explain the anomalies of EM scattering from sea surfaces and help us understand the scattering mechanism about the breaking wave more completely. 展开更多
关键词 FLUENT turbulence structure EM scattering high polarization ratios
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Large eddy simulation of turbulent statistical and transport properties in stably stratified fows
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作者 邱翔 黄永祥 +1 位作者 卢志明 刘宇陆 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2009年第2期153-162,共10页
Three dimensional large eddy simulation (LES) is performed in the investigation of stably stratified turbulence with a sharp thermal interface. Main results are focused on the turbulent characteristic scale, statist... Three dimensional large eddy simulation (LES) is performed in the investigation of stably stratified turbulence with a sharp thermal interface. Main results are focused on the turbulent characteristic scale, statistical properties, transport properties, and temporal and spatial evolution of the scalar field. Results show that the buoyancy scale increases first, and then goes to a certain constant value. The stronger the mean shear, the larger the buoyancy scale. The overturning scale increases with the flow, and the mean shear improves the overturning scale. The flatness factor of temperature departs from the Gaussian distribution in a fairly large region, and its statistical properties are clearly different from those of the velocity fluctuations in strong stratified cases. Turbulent mixing starts from small scale motions, and then extends to large scale motions. 展开更多
关键词 stratified turbulence turbulent mixing turbulent transport turbulence structure
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The Characteristics of Turbulence Structure and Transfer over the Middle Area of the Tibetan Plateau
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作者 LI Fu-Yu LI Xiao-Lan ZHANG Hong-Sheng 《Atmospheric and Oceanic Science Letters》 CSCD 2013年第2期67-73,共7页
In this paper, turbulent data obtained from the Damxung site during the Secondary Tibetan Plateau Science Experiment (TIPEX) in 1998 are used to study the characteristics of the turbulent spectra, turbulence transport... In this paper, turbulent data obtained from the Damxung site during the Secondary Tibetan Plateau Science Experiment (TIPEX) in 1998 are used to study the characteristics of the turbulent spectra, turbulence transport, and the dissipation rates of turbulent kinetic energy, temperature variance, and humidity variance in the middle area of the Tibetan Plateau. The turbulent spectra of wind velocity, potential temperature, and humidity satisfy the-2/3 power law in the high frequency range. Horizontal transportation of heat and water vapor is negligible compared with vertical transportation under strong unstable conditions, and as the stability parameter z/L increases (where z is the observational height, and L is the Monin Obukhov length), horizontal transportation becomes dominant under near-neutral, neutral, and stable conditions. The non-dimensional temperature and humidity variances are 20% less than the temperature and humidity gradient variances. These deficits appear to increase as the absolute stability parameter increases. Moreover, the effects of turbulence transportation and pressure variance exist throughout the entire stability region. 展开更多
关键词 turbulence structure turbulence transfer dissipation rate observational method Tibetan Plateau
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Effects of mean shear on the vortex identification and the orientation statistics 被引量:1
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作者 Tianyi Bai Cheng Cheng Lin Fu 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第4期280-286,共7页
This work compares the threshold applied to the swirling strength as well as the vortex orientation statistics in the total and fluctuating velocity fields using direct numerical simulations of compressible and incomp... This work compares the threshold applied to the swirling strength as well as the vortex orientation statistics in the total and fluctuating velocity fields using direct numerical simulations of compressible and incompressible turbulent channel flows.It is concluded that the difference in the swirling strength for vortex identification is minimal in the logarithmic region such that these two situations share the same threshold.Regarding the vortex orientation,the inclination angle remains similar.However,as the wall-normal distance increases,a more and more obvious distinction is noticed for its orientation with respect to the spanwise(z)direction.It is mainly due to their intrinsic differences and attendant contrasting preference for the vortex identification,i.e.,vortices rotating in the−z direction for the total velocity field and in the z direction for the fluctuating one.These observations function as a reasonable explanation for various remarks in previous studies. 展开更多
关键词 VORTEX Compressible wall-bounded turbulence Turbulence structure Channel flows
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SOME CHARACTERISTICS OF LOW-SPEED STREAKS UNDER SHEARED AIR-WATER INTERFACES 被引量:2
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作者 王双峰 贾复 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2001年第2期115-124,共10页
The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structu... The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed. 展开更多
关键词 air-water interface low-speed streak turbulent coherent structure flow visualization
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Detached-eddy simulation of turbulent coherent structures around groynes in a trapezoidal open channel 被引量:2
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作者 Jing-xin Zhang Jian Wang +1 位作者 Xiang Fan Dongfang Liang 《Journal of Hydrodynamics》 SCIE EI CSCD 2020年第2期326-336,共11页
The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation(DES).A series of short groynes were included on a 1:3 side slope of the channel.T... The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation(DES).A series of short groynes were included on a 1:3 side slope of the channel.This work focuses on the turbulent coherent structures around groynes on an uneven bottom.Flows around groyne fields are characterized by massive separation and highly unsteady vortices.DES can capture a wide spectrum of eddies at a lower computational cost than the large eddy simulation(LES)or direct numerical simulation(DNS).In the present work,a zonal DES model(ZDES)was used to simulate the flow around groynes.The ZDES model is a modified version of the DES designed to overcome the model-stress depletion(MSD)of the RANS/LES hybrid model.The vortex system consists of the horseshoe vortex(HV)formed at the base of the obstructions,the necklace vortex(NV)that wrapped the groyne tips near the free surface,and the shedding vortex(SV)underneath the free surface.The effects of the incident flow and local topography on the vortex evolution were investigated by analyzing the mean flow structures and the instantaneous turbulent flow fields.Some important vortices cannot be captured because of the averaging process,while some flow structures cannot be observed in the instantaneous flow.The mean flow is only a reflection of the averaging process when complex vortices are present. 展开更多
关键词 Open channel flow groyne free surface detached eddy simulation turbulent coherent structure
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EFFECTS OF SPLITTER BLADES ON THE LAW OF INNER FLOW WITHIN CENTRIFUGAL PUMP IMPELLER 被引量:16
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作者 YUAN Shouqi ZHANG Jinfeng YUAN Jianping HE Youshi FU Yuedeng 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第5期59-63,共5页
Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carfled out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. ... Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carfled out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test. 展开更多
关键词 Centrifugal pump Splitter blades turbulent kinetic energy structure of "jet-wake"Blade loading
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A New Approach to the Theory of Turbulence 被引量:1
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作者 吴峰 《Journal of Shanghai University(English Edition)》 CAS 2005年第3期189-193,共5页
On the basis of the fact that physical world possesses hierarchical structure and the concepts of nonstandard mathematics, a new description of turbulence was presented. Fundamental equations of turbulent flows were a... On the basis of the fact that physical world possesses hierarchical structure and the concepts of nonstandard mathematics, a new description of turbulence was presented. Fundamental equations of turbulent flows were also given. It is natural in this nonstandard picture of turbulence that the closure methods are obtained and seem to be precise. 展开更多
关键词 hierarchical structure of turbulent field monad field point-average uncertainty of measurement in turbulence.
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EFFECTS OF WALL ROUGHNESS ON COHERENT STRUCTURE IN TURBULENT SHEAR FLOWS 被引量:1
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作者 LIANG ZAICHAO LIU SHIHE, Research Institute of Water Conservancy and Hydraulic Power, Wuhan University of Hydraulic and Electric Engineering, Wuhan, Hubei, P.R. China 《Journal of Hydrodynamics》 SCIE EI CSCD 1989年第1期15-21,共7页
There are many examples that fluid flows on rough wall, such as channel flow in nature, pipe flow, etc. In order to know the flow structure of real fluids, it is important to study the effects of wall roughness on coh... There are many examples that fluid flows on rough wall, such as channel flow in nature, pipe flow, etc. In order to know the flow structure of real fluids, it is important to study the effects of wall roughness on coherent structure in turbulent shear flows. The experiments were carried out in a square glass channel, which is 600cm long, with the cross section of 30×25cm^2. The flow velocity was varied from 2 to 40 cm/s. Uniform sands whose diameters were 0.0012cm, 0.2gcm, 0.385cm, 0.594cm and 0.896cm respectively were glued to the floor of the channel. The rough Reynolds number Re_Δ= U_*Δ/ν=0.04~73, where U_*is the shear velocity, Δ is the diame- ter of uniform sand, v is the kinematic viscosity coefficient. Hydrogen bubble technique for flow visualization and HWL-II hot-film anemometer for velocity mea- surement were used in the experiments. 展开更多
关键词 EFFECTS OF WALL ROUGHNESS ON COHERENT structure IN turbulent SHEAR FLOWS FLOW
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