加熱リブレット面上に発達した流れ場の乱流特性(流体工学,流体機械)

概要

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Experimental studies of a turbulent flowfield developing over the heated riblet surface were carried out in a low-speed wind tunnel. The instantaneous velocity fields were measured by using a particle image velocimetry (PIV) in a plane that was parallel to the riblet surface, and compared with those over a heated smooth surface. The reduction ratio of the skin friction coefficient over the heated riblet surface reached up to 8% for the riblet spacing of about 13 viscous wall units. This is almost the same spacing as that obtained for the non-heated condition. The streamwise and wall-normal turbulent intensities against the local time-mean velocity were decreased in their peak values for the heated riblet. The instantaneous fluctuating velocity fields obtained by subtracting the ensemble-averaged velocity from instantaneous velocity vectors revealed that the appearance of a low-speed streaky structure became more intermittent over the riblet surface. This fact suggested a reduction in turbulence production in the near-wall region. Furthermore, it was also found that a perturbation of the spanwise velocity fluctuation was restricted near the riblet surface.
2008-04-25