Conditional correlation between a passive scaler and its dissipation in a turbulent boundary layer

A study of the conditional correlation between a passive scalar and its dis sipation offers an interesting strategy for understanding turbulence proper ties associated with both large and small scales. This correlation is inves tigated with particular emphasis on the dominant coherent motions in turbul ent boundary layers; namely, sweeps and ejections, using a local cross-corr elation analysis based on the wavelet transform. Contributions to the three temperature derivatives show different features, reflecting dear "local" d epartures from isotropy. This property of coherent motions is investigated through the conditional cross-spectra inferred from the wavelet analysis, w hich provides localized scale decomposition of the quantity under considera tion, and is translated in the spectral domain. These decompositions indica te the particular coherent motions of the flow which most contribute to the conditional correlation between temperature and its dissipation.