Experiments On Buoyant Plume Dispersion In A Laboratory Convection Tank

Weil, Jeffrey; Snyder, William H.; Lawson, Robert E.; Shipman, Michael S.

doi:10.1023/a:1013874816509

Cited by 44 publications

(60 citation statements)

References 48 publications

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“…3c. Our results agree generally with all the previous studies and are in good agreement with the water-tank experiment by Weil et al (2002). The results show that i c decreases rapidly with distance from the source and reaches an asymptotic limit of about 0.35.…”

Section: ) Concentration Fluctuationssupporting

confidence: 93%

“…Figure 3b shows the contour of i c in the horizontal plume centerline ( y/z i ϭ 0). The LES results agree with previous experimental and numerical studies (Deardorff and Willis 1984;Luhar et al 2000;Weil et al 2002). As expected, the concentration fluctuation is larger at the edges of the plume, and it has the smallest values near the plume centroid.…”

Section: Skewnesssupporting

confidence: 90%

“…The vertical meandering component zm reaches a maximum value around t * ϭ 0.5, and then it decays quickly to a very small value when the plume vertical motion is constrained by the CBL boundaries and z m ϳ z. In the horizontal direction the plume motion is not limited, and the meandering component ym is in agreement with the theoretical analysis by Csanady, as reported by Weil et al (2002),…”

Section: B Meandering Componentsupporting

confidence: 90%

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Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Dosio

Arellano

2006

Journal of the Atmospheric Sciences

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The influence of the different scales of turbulent motion on plume dispersion in the atmospheric convective boundary layer (CBL) is studied by means of a large-eddy simulation (LES). In particular, the large-scale (meandering) and small-scale (relative diffusion) contributions are separated by analyzing dispersion in two reference systems: the absolute (fixed) coordinate system and the coordinate system relative to the plume's instantaneous center of mass. In the relative coordinate system, the (vertically) inhomogeneous meandering motion is removed, and only the small-scale, homogeneous turbulent motion contributes to the dispersion process.First, mean plume position, dispersion parameters (variance), and skewness of the plume position are discussed. The analysis of the third-order moments shows how the structure and the symmetry of scalar distribution are affected with respect to the turbulent characteristics of the CBL (inhomogeneity of the large-scale vertical motion) and the presence of the boundary conditions (surface and top of the CBL). In fact, the reflection of the plume by the CBL boundaries generates the presence of nonlinear crosscorrelation terms in the balance equation for the third-order moments of the plume position. As a result, the third-order moment of the absolute position is not balanced by the sum of the third-order moments of the meandering and relative plume position.Second, mean concentration and concentration fluctuations are calculated and discussed in both coordinate systems. The intensity of relative concentration fluctuation i cr , which quantifies the internal (in plume) mixing, is explicitly calculated. Based on these results, a parameterization for the probability distribution function (PDF) of the relative concentration is proposed, showing very good agreement with the LES results. Finally, the validity of Gifford's formula, which relates the absolute concentration's high-order moments to the relative concentration and the PDF of the plume centerline, is studied. It is found that due to the presence of the CBL boundaries, Gifford's formula is not able to reproduce correctly the value of the absolute mean concentration near the ground. This result is analyzed by showing that, when the plume is reflected by the CBL boundaries, the instantaneous relative plume width zЈ 2 r (t) departs from its mean value 2 r . By introducing the skewness of the relative plume position into a parameterization for the relative mean concentration, the results for the calculated mean concentration are improved.

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Section: ) Concentration Fluctuationssupporting

confidence: 93%

Section: Skewnesssupporting

confidence: 90%

Section: B Meandering Componentsupporting

confidence: 90%

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Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Dosio

Arellano

2006

Journal of the Atmospheric Sciences

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“…This approach is most commonly used in field experiments, with surface or aircraft platforms (Briggs 1993;Lenschow and Stankov 1986), as well as in laboratory experiments Deardorff 1976, 1981;Weil et al 2002) or Eulerian numerical models (Lamb 1978;Henn and Sykes 1992;Mason 1992). In the Lagrangian framework, the statistical properties are calculated in a reference frame that moves with the flow.…”

Section: Introductionmentioning

confidence: 99%

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Dosio

Arellano

Holtslag

et al. 2005

Journal of the Atmospheric Sciences

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Eulerian and Lagrangian statistics in the atmospheric convective boundary layer (CBL) are studied by means of large eddy simulation (LES). Spectra analysis is performed in both the Eulerian and Lagrangian frameworks, autocorrelations are calculated, and the integral length and time scales are derived. Eulerian statistics are calculated by means of spatial and temporal analysis in order to derive characteristic length and time scales. Taylor's hypothesis of frozen turbulence is investigated, and it is found to be satisfied in the simulated flow.Lagrangian statistics are derived by tracking the trajectories of numerous particles released at different heights in the turbulent flow. The relationship between Lagrangian properties (autocorrelation functions) and dispersion characteristics (particles' displacement) is studied through Taylor's diffusion relationship, with special emphasis on the difference between horizontal and vertical motion. Results show that for the horizontal motion, Taylor's relationship is satisfied. The vertical motion, however, is influenced by the inhomogeneity of the flow and limited by the ground and the capping inversion at the top of the CBL. The Lagrangian autocorrelation function, therefore, does not have an exponential shape, and consequently, the integral time scale is zero. If distinction is made between free and bounded motion, a better agreement between Taylor's relationship and the particles' vertical displacement is found.Relationships between Eulerian and Lagrangian frameworks are analyzed by calculating the ratio ␤ between Lagrangian and Eulerian time scales. Results show that the integral time scales are mainly constant with height for z/z i Ͻ 0.7. In the upper part of the CBL, the capping inversion transforms vertical motion into horizontal motion. As a result, the horizontal time scale increases with height, whereas the vertical one is reduced. Current parameterizations for the ratio between the Eulerian and Lagrangian time scales have been tested against the LES results showing satisfactory agreement at heights z/z i Ͻ 0.7.

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“…Taken together, the PDF results show more exponential-like distributions at the plume edge, particularly the lower edge, than in the plume centre. The intermittency, I, is small at the plume centre at x/H = 0.1, which favours clipped-Gaussian-like forms, but is much larger at the edges, favouring exponential forms [6,7,40,41].…”

Section: Intermittency Of the Concentration Time Seriesmentioning

confidence: 97%

Statistical properties of concentration fluctuations in two merging plumes

2013

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The statistics of the fluctuating concentration field within a plume is important in the analysis of atmospheric dispersion of toxic, inflammable and odorous gases. Previous work has tended to focus on concentration fluctuations in single plumes released in the surface layer or at ground level and there is a general lack of information about the mixing of two adjacent plumes and how the statistical properties of the concentration fluctuations are modified in these circumstances. In this work, data from wind tunnel experiments are used to analyse the variance, skewness, kurtosis, intermittency, probability density function and power spectrum of the concentration field during the mixing of two identical plumes and results are compared with those obtained for an equivalent single plume. The normalised variance, skewness and kurtosis on the centre-lines of the combined plume increase with distance downwind of the stack and, in the two-source configuration, takes lower values than those found in the single plumes. The results reflect the merging process at short range, which is least protracted for cases in which the sources are in-line or up to 30 • off-line. At angles of 45 • and more, the plumes are effectively side-by-side during the merging process and the interaction between the vortex pairs in each plume is strong. Vertical asymmetry is observed between the upper and the lower parts of the plumes, with the upper part having greater intermittency (i.e. the probability that no plume material is present) and a more pronounced tail to the concentration probability distribution. This asymmetry tends to diminish at greater distances from the source but occurs in both buoyant and neutral plumes and is believed to be associated with the 'bending-over' of the emission in the cross-flow and the vortex pair that this generates. The results allowed us to identify three phases in plume development. The first, very near the stack, is dominated by turbulence generated within the plume and characterised by concentration spectra with distinct peaks corresponding to scales comparable with those of the counter-rotating vortex pair. A second phase follows at somewhat greater distances 123Environ Fluid Mech downwind, in which there are significant contributions to the concentration fluctuations from both the turbulence internal to the plume and the external turbulence. The third phase is one in which the concentration fluctuations appear to be controlled by the external turbulence present in the ambient flow.

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Experiments On Buoyant Plume Dispersion In A Laboratory Convection Tank

Cited by 44 publications

References 48 publications

Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Statistical properties of concentration fluctuations in two merging plumes

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