Correlating data: examples from turbulent wall layers

Flow fields in fluid mechanics often contain regions where different physical events occur. The relative size of the regions changes as a parameter is varied. Correlating field data, either physical or DNS calculation experiments, in these situations can be aided by using ideas from matched asymptotic expansions from applied mathematics. A second situation is when two slightly different processes occur in the same spatial region. For this case, a two-term asymptotic expansion is needed. This article discusses how composite expansions and the common part matching behavior are useful in correlating data.