共查询到19条相似文献,搜索用时 217 毫秒
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本文运用随机游动模拟方法改进建立一种粒子--烟团模式,成功地模拟了对流边界层条件下污染物扩散,粒子--烟团模式的模拟结果与水槽试验的结果吻合较好。数值模拟试验结果表明粒子--烟团模式能在旋放粒子数较少,从而运行时间很短的情况下,得到优于一般随机游动模式的模拟性能。用KNRC的资料对模拟性能作一验证,表明模式也能很好地模拟实际大气中不同稳定度情况下的扩散。 相似文献
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绿洲与荒漠相互影响下大气边界层特征的模拟 总被引:10,自引:2,他引:10
张强 《南京气象学院学报》1998,21(1):104-113
用发展的二维中尺度土壤-植被-大气连续体数值模式模拟了绿洲与荒漠相互影响下的大气边界层特征。得到了绿洲和临近荒漠之间的边界层高度、风螺线、风速廓线、位温廓线和比湿廓线的差别,并给出了绿洲对其上游和下游荒漠大气的不同影响。基本再现了白天绿洲大气逆温和临近绿洲的荒漠大气逆湿。模拟实验研究不仅验证了外场观测结果,而且也使我们对复杂下垫面边界层结构有了一些新的认识。 相似文献
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本文运用随机游动模拟方法改进建立一种粒子—烟团模式,成功地模拟了对流边界层条件下污染物扩散,粒子—烟团模式的模拟结果与水槽试验的结果吻合较好。数值模拟试验结果表明粒子—烟团模式能在施放粒子数较少,从而运行时间很短的情况下,得到优于一般随机游动模式的模拟性能。用KNRC的资料对模式的模拟性能作一验证,表明模式也能很好地模拟实际大气中不同稳定度情况下的扩散。 相似文献
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Arnaldo Longhetto Enrico Ferrero 张瑛 全利红 Massimiliano Manfrin Luca Mortarini Renato Forza 《气象与减灾研究》2009,32(3):15-18
重点介绍和讨论了中性条件下旋转扰动流体中边界层强迫不稳定及其相关的一些问题,阐述了旋转体系中切变驱动边界层不稳定的动力学特征。这些不稳定状态的研究在大气物理学、流体动力学、海洋学等多个领域中引起科学家极大的兴趣,近年来在实验和理论研究中都得到了不断的发展。意大利都灵大学基础物理系地球科学实验组通过水槽旋转实验方法,不断改变水槽启动或结束时的旋转运动速度,以及底部壁面粗糙度等要素,所得到的实验结果与SDBL理论非常一致。 相似文献
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重点介绍和讨论了中性条件下旋转扰动流体中边界层强迫不稳定及其相关的一些问题,阐述了旋转体系中切变驱动边界层不稳定的动力学特征.这些不稳定状态的研究在大气物理学、流体动力学、海洋学等多个领域中引起科学家极大的兴趣,近年来在实验和理论研究中都得到了不断的发展.意大利都灵大学基础物理系地球科学实验组通过水槽旋转实验方法,不断改变水槽启动或结束时的旋转运动速度,以及底部壁面粗糙度等要素,所得到的实验结果与SDBL理论非常一致. 相似文献
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主要从理论、试验角度对大气边界层的研究进行了简要的回顾,尤其对近年来倍受关注的非均匀地表条件下的边界层研究进行了较详细的介绍,并对大气边界层的研究进行了展望。20世纪50年代,Monin和Obukhov提出的Monin-Obukhov相似理论,为现代大气边界层物理学奠定了基础。之后进行的多次大型综合性外场试验,不仅揭示和发现了大气边界层中的许多现象和规律,也验证和发展了Monin-Obukhov相似理论。80年代以后,非均匀地表条件下的大气边界层研究越来越受到关注,一些新的现象被揭示,新的问题被提出,同时也提出了一些新的概念和研究方法。未来10 a,除大气湍流机理等需长期坚持研究外,还应进一步开展非均匀复杂下垫面边界层研究、城市边界层研究和局地边界层气象预报研究。 相似文献
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大气边界层高度确定及应用研究进展 总被引:2,自引:0,他引:2
大气边界层高度是表征边界层特征的重要参量,影响边界层内水热、物质、能量的垂直分布,也是数值模拟、环境评估中的重要参数。从湍流运动、热力作用、动力作用以及物质分布等多视角总结了大气边界层高度的定义及确定方法,回顾了采用直接观测手段和遥感手段确定大气边界层高度的不同方法,对比了大气边界层高度不同获取手段的优缺点,梳理了大气边界层高度参数化方案,探讨了大气边界层高度确定中存在的问题,并提出未来相关研究和应用可能突破方向。 相似文献
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本文建立了二阶矩闭合的大气边界层数值模式,并模拟了Wangara资料第33天09:00—18:00时对流边界层的发展过程。计算结果与实测资料比较吻合,同时利用该模式研究了高阶矩模式模拟对流边界层的可行性,结果指出:二阶矩方程中的湍流扩散项对模拟对流边界层内的挟卷和反梯度现象起主要作用。而局地时间变化项仅影响对流边界层内的边界湍流扩散项。因此,假如处理好二阶矩方程中的湍流扩散项,高阶矩模式和大涡模式一样可以很好地模拟对流边界层的发生、发展。 相似文献
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A Large-Eddy Simulation and Lagrangian Stochastic Study of Heavy Particle Dispersion in the Convective Boundary Layer 总被引:4,自引:1,他引:4
Large-eddy simulation and Lagrangian stochastic dispersion models were used to study heavy particle dispersion in the convective boundary layer (CBL). The effects of various geostrophic winds, particle diameters, and subgrid-scale (SGS) turbulence were investigated. Results showed an obvious depression in the vertical dispersion of heavy particles in the CBL and major vertical stratification in the distribution of particle concentrations, relative to the passive dispersion. Stronger geostrophic winds tended to increase the dispersion of heavy particles in the lower CBL. The SGS turbulence, particularly near the surface, markedly influenced the dispersion of heavy particles in the CBL. For reference, simulations using passive particles were also conducted; these simulation results agreed well with results from previous convective tank experiments and numerical simulations. 相似文献
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一个对流边界层中的随机扩散模式 总被引:1,自引:0,他引:1
通过对对流边界层(CBL)湍流结构的分析,首次提出用两种不同尺度的湍流模拟CBL中的铅直扩散.在此基础上发展了一个随机扩散模式,并用它模拟了典型对流条件下两种高架连续点源的扩散.与Willis水槽模拟和Lamb等人数值模拟以及CONDORS计划外场试验的结果的比较表明,本模式能成功地模拟CBL中的横向积分浓度.与其它数值模式相比,还具有输入参数少、计算量极小和更加简单实用的优点. 相似文献
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The convective boundary layer (CBL) with a wide range of stability is simulated experimentally using a thermally stratified wind tunnel, and numerically by direct numerical simulation (DNS). The turbulence structures and flow characteristics of various CBL flows, capped by a strong temperature inversion and affected by surface shear, are investigated. The various vertical profiles of turbulence statistics similar to those from the observed CBL in the field are successfully simulated in both the wind-tunnel experiment and in DNS. The comparison of the wind-tunnel data and DNS results with those of atmospheric observations and water-tank studies shows the crucial dependence of the turbulence statistics in the upper part of the layer on the strength of the inversion layer, as well as the modification of the CBL turbulence regime by the surface shear. 相似文献
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利用宜昌2007年12月10-25日的加密观测资料,分析了两次低值系统经过宜昌时大气边界层的温湿风廓线结构及其日变化特征。结果表明:位温廓线具有明显的日变化特征,对流边界层在白天出现和发展,其高度可达600m,而稳定边界层在夜间出现和发展,其高度可达300m,降水会抑制对流边界层和稳定边界层的发展;湿度廓线结构及其日变化与对流边界层的发展有关,总体上湿度随高度减小,贴近地面的薄层湿度随高度减小较快,而混合层内湿度随高度变化较小,出现降水时,近地层的湿度有明显增加,大气边界层内湿度随高度快速平稳减小;风速廓线结构比较复杂,总体上风速随高度增大,在大气边界层低层有时会出现一个风速极大值,风速廓线没有明显的日变化特征,大气边界层内风向变化较大,但以偏东风为主。 相似文献
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Development of the Convective Boundary Layer Capping with a Thick Neutral Layer in Badanjilin: Observations and Simulations 总被引:1,自引:0,他引:1
In this study,the development of a convective boundary layer (CBL) in the Badanjilin region was investigated by comparing the observation data of two cases.A deep neutral layer capped a CBL that occurred on 30 August 2009.This case was divided into five sublayers from the surface to higher atmospheric elevations:surface layer,mixed layer,inversion layer,neutral layer,and sub-inversion layer.The development process of the CBL was divided into three stages:S1,S2,and S3.This case was quite different from the development of the three-layer CBL observed on 31 August 2009 because the mixed layer of the five-layer CBL (CBL5) eroded the neutral layer during S2.The specific initial structure of the CBL5 was correlated to the synoptic background of atmosphere during nighttime.The three-stage development process of the CBL5 was confirmed by six simulations using National Center for Atmospheric Research (USA) large-eddy simulation (NCAR-LES),and some of its characteristics are presented in detail. 相似文献
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A laboratory study of the turbulent velocity characteristics in the convective boundary layer 总被引:4,自引:0,他引:4
Based on the measurement of the velocity field in the convective boundary layer (CBL) in a convection water tank with the particle image velocimetry (PIV) technique, this paper studies the characteristics of the CBL turbulent velocity in a modified convection tank. The experiment results show that the velocity distribution in the mixed layer clearly possesses the characteristics of the CBL thermals, and the turbulent eddies can be seen obviously. The comparison of the vertical distribution of the turbulent velocity variables indicates that the modeling in the new tank is better than in the old one. The experiment data show that the thermal's motion in the entrainment zone sometimes fluctuates obviously due to the intermittence of turbulence. Analyses show that this fluctuation can influence the agreement of the measurement data with the parameterization scheme, in which the convective Richardson number is used to characterize the entrainment zone depth. The normalized square velocity wi^2/w*^2. at the top of the mixed layer seems to be time-dependent, and has a decreasing trend during the experiments. This implies that the vertical turbulent velocity at the top of the mixed layer may not be proportional to the convective velocity (w*). 相似文献
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Peter Hurley 《Boundary-Layer Meteorology》2007,125(3):525-536
The treatment of turbulence closure in atmospheric models is examined in the context of the dry convective boundary layer
(CBL) and the eddy-diffusivity/mass-flux (EDMF) approach. The EDMF approach is implemented into a model called TAPM to use
a coupled two-equation prognostic turbulence closure and the mass-flux approach to represent turbulence in the CBL. This work
also extends the range of turbulence variables that can be derived from the mass-flux component of the model and uses these
along with their values from the prognostic scheme to provide total turbulence fields that can be used to compare to data
and/or to feed into other components of TAPM, including those needed to drive Eulerian and Lagrangian air pollution dispersion
modules. Model results are presented for the afternoon of a simulated summer day and are compared to both laboratory and field
observations in a mixed-layer scaled framework. The results show that the EDMF approach works well within TAPM and can provide
good predictions of mean and turbulence fields, including in the upper levels of the CBL. The EDMF approach has several attractive
features, including the potential to be one approach to unify the treatment of turbulence and dry and moist convection in
atmospheric models. 相似文献
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实验速度场测量技术及对流边界层特征研究 总被引:3,自引:0,他引:3
在对流槽中对对流边界层(CBL)温度场实验研究的基础上,进一步尝试通过实验技术测量速度场并分析研究CBL中的速度场特征。在应用PIV测量技术时选用铝粉作示踪粒子。实验证明了在混合层中速度分布明显具有对流边界层热泡特性;混合层顶部的速度分布很好地反应出夹卷层的结构特征;湍流速度特征量的垂直分布合理,与野外实测结果和类似的对流槽实验结果接近;误差分析表明示踪粒子的跟随性良好,粒子速度的测量结果能真实地反应流体的运动特征,从而得证了分析结果的可靠性。 相似文献