Journal
BOUNDARY-LAYER METEOROLOGY
Volume 167, Issue 3, Pages 349-369Publisher
SPRINGER
DOI: 10.1007/s10546-017-0330-6
Keywords
Concentration statistics; Fluctuating plume; Gamma distribution; Lagrangian stochastic model; Micromixing modelling
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Funding
- European Research Council (ERC) under the European Unions Horizon research and innovation programme [670462]
- European Research Council (ERC) [670462] Funding Source: European Research Council (ERC)
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We analyze the reliability of the Lagrangian stochastic micromixing method in predicting higher-order statistics of the passive scalar concentration induced by an elevated source (of varying diameter) placed in a turbulent boundary layer. To that purpose we analyze two different modelling approaches by testing their results against the wind-tunnel measurements discussed in Part I (Nironi et al., Boundary-Layer Meteorology, 2015, Vol. 156, 415-446). The first is a probability density function (PDF) micromixing model that simulates the effects of the molecular diffusivity on the concentration fluctuations by taking into account the background particles. The second is a new model, named VP Gamma, conceived in order to minimize the computational costs. This is based on the volumetric particle approach providing estimates of the first two concentration moments with no need for the simulation of the background particles. In this second approach, higher-order moments are computed based on the estimates of these two moments and under the assumption that the concentration PDF is a Gamma distribution. The comparisons concern the spatial distribution of the first four moments of the concentration and the evolution of the PDF along the plume centreline. The novelty of this work is twofold: (i) we perform a systematic comparison of the results of micro-mixing Lagrangian models against experiments providing profiles of the first four moments of the concentration within an inhomogeneous and anisotropic turbulent flow, and (ii) we show the reliability of the VP Gamma model as an operational tool for the prediction of the PDF of the concentration.
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