ISSN:
1573-1472
Keywords:
Conditional concentration statistics
;
Mixing
;
Scalar dissipation
;
Turbulence
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract We analyse cross-wind-integrated statistics of theconcentration field of a conserved scalar for pointand line sources in grid turbulence. In particular,using wind-tunnel measurements we calculate thecross-wind integrated probability density function(pdf) for the scalar concentration. We then use thatquantity in the exact evolution equation for the pdfto calculate the cross-wind integrated mean of therate of dissipation of scalar variance, conditional onthe scalar concentration. Much of the variation ofthese statistics with distance downstream is accountedfor by scaling with concentration, length and timescales based on the development of the mean plume.This scaling thus suggests some simple practicalparameterisations of these statistics in terms ofmean-field quantities. One of the motivations for thiswork is to find a simple parameterisation for thescalar dissipation that can be used for modellingchemical reactions in plumes. We also consider the cross-wind integral of the firstfew moments of the concentration field and show thatthe integration greatly simplifies the budgets forthese moments. Thus the first moment is just thedownstream flux of the scalar, which is constant. Thesecond moment budget provides a check on the meandissipation estimated directly from the pdf evolutionequation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1002794510020
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