Lognormality of the scalar dissipation pdf in turbulent flows

It is shown that measurements of lower‐dimensional projections of the scalar gradient in an isotropic conserved scalar field ζ(x,t) are sufficient to construct the probability density function (pdf) for the true scalar dissipation χ. With this general method, the true scalar dissipation pdf is obtained from the result reported recently for the approximate pdf based on ‖∇ζ‖2≈3⋅(∂ζ/∂x)2. Results show that (i) the pdf of the true scalar dissipation is virtually lognormal and (ii) the most probable value of χ increases and the rms fluctuations of χ decrease in comparison with their one‐dimensional estimates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70557/2/PFADEB-1-7-1290-1.pd