SPATIAL-RESOLUTION IN THE MEASUREMENT OF CONCENTRATION FLUCTUATIONS

In a turbulent Bow, a miscible contaminant is confined to sheets and s trands of the very thin Batchelor conduction cut-off length. This fact has been surmised for some time and has recently been observed direct ly through high precision measurements. This fine-scaled texture of th e contaminant concentration held makes it an extraordinary challenge t o achieve (experimentally) adequate continuum scale resolution, partic ular ly in important environmental flows such as the atmospheric bound ary layer. In this paper, an extrapolation scheme is proposed whereby the systematic measurement (with known sample volumes) of the lower-or der moments of the concentration fluctuations are used to approximate the true, perfectly resolved values, and hence to approximate the true probability density function. Such a scheme relies on empirical data, and so the need fur more experiments designed to investigate the effe cts of spatial resolution cannot be over-emphasized.