Measurement of streamwise vorticity fluctuations in a turbulent channel flow

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Abstract
In a fully developed turbulent channel flow, measurements of the streamwise vorticity fluctuations ωx have been made. A newly designed probe provides simultaneously in addition to the vorticity signal all three velocity signals. The new probe bears a likeness to the Kovasznay-type vorticity probe, but consists of four electrically independent hot wires, each mounted separately on a total of eight supporting prongs. A new calibration technique had to be developed for this probe.In addition to various statistical properties of the three velocity components, the distributions of vorticity fluctuations and of skewness and flatness factors are given up to wall distances as close as y+ = 19. A pronounced maximum of the streamwise vorticity fluctuations was found at y+ ≈ 20. Large values of the flatness factor characterize the outer flow region.