Multiple line Molecular Tagging Velocimetry (MTV) measurements are used to explore the flow fields associated with wall region negative ∂u˜/∂y in a low Rθ turbulent boundary layer. Velocity and velocity gradient statistical profiles establish the present flow as a canonical flat plate boundary layer. Spatial correlations of ∂u/∂y in the (x, y) plane, and the probability of observing negative ∂u˜+/∂y+ exceeding a negative threshold of −0.25 reveal the highly significant presence of negative ∂u˜/∂y in the region 25 ≤ y+ ≤ 35. Examination of the instantaneous flow fields underlying the conditional pdf indicates that there are two primary contributing motions: (i) streamwise shear layers and (ii) compact regions containing ±∂u˜/∂y. The importance of these motions to wall region turbulence production is discussed.

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