Measurements of spanwise and streamwise velocity components in a turbulent spot artificially initiated in a Blasius boundary layer are described. A special hot-wire rake consisting of 8 ‘V’ shaped arrays was built for this purpose. This multi-probe rake also enabled one to align the individual realizations in both streamwise and spanwise directions and to form more representative ensemble-averages near the tip of the spot. The data reveals the existence of a strong spanwise component of velocity which attains its maximum value at the tip of the spot and is centered around an elevation equivalent to the displacement thickness of the unperturbed boundary layer. This perturbation velocity resembles a wave which follows the leading interface of the spot and may therefore be amenable to analysis.
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