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1.
Ｉ．ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｅ１９８０ｓ,ｉｔｈａｓｂｅｎｆｏｕｎｄｔｈａｔｓｏｍｅａｔｍｏｓｐｈｅｒｉｃｄｉｓｐｅｒｓｉｏｎｍｏｄｅｌｓｆｏｒｃｏｎｖｅｎｔｉｏｎａｌａｐｐｌｉｃａｔｉｏｎｓａｒｅｎｏｔｇｏｏｄｉｎｃｏｉｎｃｉｄｉｎｇ... 相似文献
2.
考虑环境湍流作用的烟气上升路径方程 总被引：1，自引：3，他引：1
本文利用我国的观测资料对中性层结时的烟气拾升路径作了细致的分析。发现抬升高度与距离之间符合幂次关系,但与不考虑环境湍流作用的2/3次律有系统偏离;这一偏离与烟流半径和高度的非线性关系相一致。上述事实与国外的一些观测结果均表明,环境湍流对烟气抬升的累积作用不容忽视。为此,提出了环境湍流与自生湍流的联合作用模式,由此导得的抬升路径方程可以满意地解释上述观测事实。模式还显示,卷挟速度除取决于切变速度及湍流强度以外,还是烟流半径的函数,因而在物理上更加合理。由联合作用模式导出的终极抬升公式比不考虑环境湍流累积作用的公式更符合观测结果。 相似文献
3.
Ashok K. Luhar 《Boundary-Layer Meteorology》2002,102(1):1-38
The mean concentration distributionwithin a plume released from a point source in the atmosphericboundary layer can be greatly influenced by the systematic turningof wind with height (i.e. vertical wind direction shear). Such aninfluence includes a deflection of the plume centroid, with anassociated shearing of the vertical plume cross-section, and anenhancement of dispersion, in the horizontal plane. Wind directionshear is normally not accounted for in coastal fumigation models,although dispersion observations with shear acting as acontrolling parameter are not uncommon. A three-dimensionalLagrangian stochastic model is used to investigate the influenceof uniform wind direction shear on the diffusion of a point-sourceplume within the horizontally homogeneous convective boundarylayer, with the source located at the top of the boundary layer.Parameterisations are developed for the plume deflection andenhanced dispersion due to shear within the framework of aprobability density function (PDF) approach, and compared with theLagrangian model results. These parameterisations are thenincorporated into two applied coastal fumigation models: a PDFmodel, and a commonly used model that assumes uniform andinstantaneous mixing in the vertical direction. The PDF modelrepresents the vertical mixing process more realistically. A moreefficient version of the PDF model, which assumes a well-mixedconcentration distribution in the vertical at large times, isapplied to simulate sulfur dioxide data from the Kwinana CoastalFumigation Study. A comparison between the model results and thedata show that the model performs much better when the wind-sheareffects are included. 相似文献
4.
环境湍流对烟云抬升的作用 总被引：2，自引：1，他引：2
本文研究了中性层结环境中湍流对烟云抬升的连续作用。取外部湍流卷挟率正比于湍流特征速度并叠加于自身卷挟率,分析表明,即使在抬升的早期,环境湍流对弯曲烟云的路径有不可忽视的影响,并使烟云路径加速变平。电厂烟云的实测资料表明,平均抬升路径实际上不完全符合无湍流环境的三分之二规律,而与本文理论结果更为接近。 本研究也发现,最大抬升高度及其出现的下风距离都是大气湍流度的灵敏函数。据此,我们分析了几个常用抬升公式的局限性,并推荐了一种反映大气湍流度的改型公式。 相似文献
5.
对几种烟云抬升模式进行了比较,分析了中性层结下环境湍流的对烟云抬升的作用,认为环境流连续作用于烟云抬升的各个阶段,且随烟云抬升而变化。抬升高度与环境湍流有关,湍流强度越大,抬升越低。 相似文献
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Experimental data for buoyant plumes released from high sources into layers having little ambient turbulence show that plume dispersion parameters vary in a manner similar to that during initial plume rise. This is consistent with general plume rise theory. Dispersion of plumes from tall stacks in a shoreline environment where a thermal internal boundary layer is formed often demonstrates this behaviour. 相似文献
9.
This paper has investigated the rise of bent-over buoyant plume in neutral condition.By means of the combined-effect model proposed at earlier time,authors have deduced a formula of final rise limited by mechanical turbulence and therefore have concluded that the corresponding formula neglecting the accumulated effect of ambient turbulence is only its particular case.By analyzing the function relation of the various affecting factors with the plume rise in the existing equations,it is proved that the formula derived from the combined-effect model is the most reasonable and shows more conformity to the observations. 相似文献
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11.
Pietro Salizzoni Raphaël Van Liefferinge Patrick Mejean Lionel Soulhac Richard J. Perkins 《Boundary-Layer Meteorology》2010,135(3):455-467
The influence of surface roughness on the dispersion of a passive scalar in a rough wall turbulent boundary layer has been
studied using wind-tunnel experiments. The surface roughness was varied using different sizes of roughness elements, and different
spacings between the elements. Vertical profiles of average concentration were measured at different distances downwind of
the source, and the vertical spread of the plume was computed by fitting a double Gaussian profile to the data. An estimate
of the integral length scale is derived from the turbulence characteristics of the boundary layer and is then used to scale
the measured values of plume spread. This scaling reduces the variability in the data, confirming the validity of the model
for the Lagrangian integral time scale, but does not remove it entirely. The scaled plume spreading shows significant differences
from predictions of theoretical models both in the near and in the far field. In the region immediately downwind of the source
this is due to the influence of the wake of the injector for which we have developed a simple model. In the far field we explain
that the differences are mainly due to the absence of large-scale motions. Finally, further downwind of the source the scaled
values of plume spread fall into two distinct groups. It is suggested that the difference between the two groups may be related
to the lack of dynamical similarity between the boundary-layer flows for varying surface roughness or to biased estimates
of the plume spread. 相似文献
12.
Field and laboratory studies have been conducted to investigate the effect of surrounding buildings on the plume rise from low-level buoyant sources, such as distributed power generators. The field experiments were conducted in Palm Springs, California, USA in November 2010 and plume rise from a 9.3 m stack was measured. In addition to the field study, a laboratory study was conducted in a water channel to investigate the effects of surrounding buildings on plume rise under relatively high wind-speed conditions. Different building geometries and source conditions were tested. The experiments revealed that plume rise from low-level buoyant sources is highly affected by the complex flows induced by buildings stationed upstream and downstream of the source. The laboratory results were compared with predictions from a newly developed numerical plume-rise model. Using the flow measurements associated with each building configuration, the numerical model accurately predicted plume rise from low-level buoyant sources that are influenced by buildings. This numerical plume rise model can be used as a part of a computational fluid dynamics model. 相似文献
13.
Summary Extreme values of the ground level concentration of air pollutants were evaluated as a function of plume rise Δh, and wind speed in two cases. Firstly, when a plume rise depends on the downwind distance x, and secondly, with a constant plume rise (i.e., independent on x). Also, the extreme values for the effective stack height were evaluated for different stability classes. The maximum value
of the ground level concentration was obtained in unstable stability when plume rise depends on x and in the neutral stability when plume rise independent on x. Also, in stable case, the extreme values of the ground level concentration of air pollutants showed similar values in the
two cases when plume rise depends on x, and with constant plume rise. Finally, it was found that the extreme value of the ground level concentration occurred near
the stack and after that it was decreases in all stabilities. 相似文献
14.
B. J. Devenish G. G. Rooney H. N. Webster D. J. Thomson 《Boundary-Layer Meteorology》2010,134(3):411-439
We consider large-eddy simulations (LES) of buoyant plumes from a circular source with initial buoyancy flux F
0 released into a stratified environment with constant buoyancy frequency N and a uniform crossflow with velocity U. We make a systematic comparison of the LES results with the mathematical theory of plumes in a crossflow. We pay particular
attention to the limits [(U)\tilde] << 1{\tilde{U}\ll1} and [(U)\tilde] >> 1{\tilde{U}\gg 1}, where [(U)\tilde]=U/(F0 N)1/4{\tilde{U}=U/(F_0 N)^{1/4}}, for which analytical results are possible. For [(U)\tilde] >> 1{\tilde{U}\gg 1}, the LES results show good agreement with the well-known two-thirds law for the rise in height of the plume. Sufficiently
far above the source, the centreline vertical velocity of the LES plumes is consistent with the analytical z
−1/3 and z
−1/2 scalings for respectively [(U)\tilde] << 1{\tilde{U}\ll 1} and [(U)\tilde] >> 1{\tilde{U}\gg 1}. In the general case, where the entrainment is assumed to be the sum of the contributions from the horizontal and vertical
velocity components, we find that the discrepancy between the LES data and numerical solutions of the plume equations is largest
for [(U)\tilde]=O(1){\tilde{U}=O(1)}. We propose a modified additive entrainment assumption in which the contributions from the horizontal and vertical velocity
components are not equally weighted. We test this against observations of the plume generated by the Buncefield fire in the
U.K. in December 2005 and find that the results compare favourably. We also show that the oscillations of the plume as it
settles down to its final rise height may be attenuated by the radiation of gravity waves. For [(U)\tilde] << 1{\tilde{U}\ll 1} the oscillations decay rapidly due to the transport of energy away from the plume by gravity waves. For ${\tilde{U}>rsim 1}${\tilde{U}>rsim 1} the gravity waves travel in the same direction and at the same speed as the flow. In this case, the oscillations of the plume
do not decay greatly by radiation of gravity waves. 相似文献
15.
Eugene Yee R. Chan P. R. Kosteniuk G. M. Chandler C. A. Biltoft J. F. Bowers 《Boundary-Layer Meteorology》1995,76(1-2):41-67
This paper describes a study of the vertical structure of concentration fluctuations in a neutrally buoyant plume from an elevated point source in slightly convective to moderately stable meteorological conditions at ranges of between 12.5 and 100 m for a range of source heights between 1 and 5 m. Observations were made of concentration fluctuations in a dispersing plume using a vertical array of sixteen very fast-response photoionization detectors placed at heights between 0.5 and 16 m. Vertical profiles of a number of concentration statistics were extracted, namely, mean concentration, fluctuation intensity, intermittency factor, peak-to-mean concentration ratio, mean dissipation rate of concentration variance, and various concentration time and length scales of dominant motions in the plume (e.g., integral macro-scale, in-plume mid-scale and Taylor micro-scale). The profiles revealed a similarity to corresponding crosswind profiles for a fully elevated plume, but showed greater and greater departure from the latter shapes once the plume had grown in the vertical so that its lower dege began to interact progressively more strongly with the ground. The evolution of the concentration probability density function at a fixed range, but with decreasing height from the ground, is similar to that obtained at a fixed height but with increasing distance from the source. Concentration power spectra obtained at different heights all had an extensive inertial-convective subrange spanning at least two decades in frequency, but spectra measured near the ground had a greater proportion of the total concentration variance in the lower frequencies (energetic subrange), with a correspondingly smaller proportion in the higher frequencies (inertial-convective subrange). It is believed that these effects result from the increased mean shear near the surface, and blocking by the surface. The effect of enhanced shear-induced molecular diffusion on concentration fluctuations is examined. 相似文献
16.
Bryan R. Kerman 《Boundary-Layer Meteorology》1979,16(4):395-408
A model of buoyancy- and momentum-driven industrial plumes in a freely convective boundary layer is proposed. The development combines the Lagrangian similarity models of Yaglom for non-buoyant releases in the convective surface layer with the Scorer similarity model for industrial plumes. Constraints on the validity of the extension of Yaglom’s model to the entire convective planetary boundary layer, arrived at by consideration of Batchelor’s formulation for diffusion in an inertial subrange, are often met in practice. The resulting formulation applies to an interval of time in which the entrainment of the atmosphere by the plume is balanced by the entrainment of the plume by the atmosphere. It is argued that during this interval, both maximum plume rise and ground contact are achieved. Further examination of the physical interrelationship with the Csanady-Briggs formulation serves to consolidate the model hypotheses, as well as to simplify the derivation of maximum ground-level concentrations. Experimental evidence is presented for the validity of the model, based on Moore’s published data. 相似文献
17.
Bryan R. Kerman 《Boundary-Layer Meteorology》1979,16(3):395-408
A model of buoyancy- and momentum-driven industrial plumes in a freely convective boundary layer is proposed. The development combines the Lagrangian similarity models of Yaglom for non-buoyant releases in the convective surface layer with the Scorer similarity model for industrial plumes. Constraints on the validity of the extension of Yaglom’s model to the entire convective planetary boundary layer, arrived at by consideration of Batchelor’s formulation for diffusion in an inertial subrange, are often met in practice. The resulting formulation applies to an interval of time in which the entrainment of the atmosphere by the plume is balanced by the entrainment of the plume by the atmosphere. It is argued that during this interval, both maximum plume rise and ground contact are achieved. Further examination of the physical interrelationship with the Csanady-Briggs formulation serves to consolidate the model hypotheses, as well as to simplify the derivation of maximum ground-level concentrations. Experimental evidence is presented for the validity of the model, based on Moore’s published data. 相似文献
18.
By D. MÜLLER B. HEINOLD M. TESCHE I. TEGEN D. ALTHAUSEN L. ALADOS ARBOLEDAS V. AMIRIDIS A. AMODEO A. ANSMANN D. BALIS A. COMERON G. D'AMICO E. GERASOPOULOS J. L. GUERRERO-RASCADO V. FREUDENTHALER E. GIANNAKAKI B. HEESE M. IARLORI P. KNIPPERTZ R. E. MAMOURI L. MONA A. PAPAYANNIS G. PAPPALARDO R.-M. PERRONE G. PISANI V. RIZI M. SICARD N. SPINELLI A. TAFURO M. WIEGNER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):325-339
We observed a long-range transport event of mineral dust from North Africa to South Europe during the Saharan Mineral Dust Experiment (SAMUM) 2006. Geometrical and optical properties of that dust plume were determined with Sun photometer of the Aerosol Robotic Network (AERONET) and Raman lidar near the North African source region, and with Sun photometers of AERONET and lidars of the European Aerosol Research Lidar Network (EARLINET) in the far field in Europe. Extinction-to-backscatter ratios of the dust plume over Morocco and Southern Europe do not differ. Ångström exponents increase with distance from Morocco. We simulated the transport, and geometrical and optical properties of the dust plume with a dust transport model. The model results and the experimental data show similar times regarding the appearance of the dust plume over each EARLINET site. Dust optical depth from the model agrees in most cases to particle optical depth measured with the Sun photometers. The vertical distribution of the mineral dust could be satisfactorily reproduced, if we use as benchmark the extinction profiles measured with lidar. In some cases we find differences. We assume that insufficient vertical resolution of the dust plume in the model calculations is one reason for these deviations. 相似文献
19.
The effects of a pressure jump and a following internal gravity wave on turbulence and plume diffusion in the stable planetary
boundary layer are examined. The pressure jump was accompanied by a sudden increase in turbulence and plume dispersion. The
effects of wave perturbations on turbulence statistics are analysed by calculating fluxes and variances with and without the
wave signal for averaging times ranging from 1 to 30 min. The wave signals are obtained using a band-pass filter. It is shown
that second-order turbulence quantities calculated without first subtracting the wave perturbations from the time are greater
than those calculated when the wave signal is separated from the turbulence. Estimates of the vertical dispersion of an elevated
tracer plume in the stable boundary layer are made using an elastic backscatter lidar. Plume dispersion observed 25 m downwind
of the source increases rapidly with the arrival of the flow disturbances. Measured plume dispersion and plume centreline
height correlate with the standard deviation of the vertical velocity but not with the wave signal. 相似文献
20.
B. Henderson-Sellers 《Boundary-Layer Meteorology》1980,19(4):495-499
The three-phase plume model (for predicting plume rise) is linked to the Gaussian plume model (for predicting dispersion from a non-buoyant source) by demonstration that the entrainment velocity associated with the third phase of the plume rise is of identical functional form to that derived for Fickian diffusion. 相似文献