1304 三次元リブレットによる抵抗低減流れのPIV計測(OS13-1 流れの抵抗低減,オーガナイズドセッション)

概要

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Experimental study of a new three-dimensional (3-D) blade riblet is carried out. The lateral spacing of our 3-D riblet surface is periodically changed in the streamwise direction. Obtained drag reduction rate is about 6% at Re_τ= 150. The flow structure over the 3-D riblet was also analyzed in instantaneous velocity fields by using 2-D particle image velocimetry on a horizontal near-wall plane and compared with the corresponding flow over the flat surface in an attempt to identify the physical mechanisms that cause drag reduction. Moreover, the spanwise two-point correlation R_<u'u>(Δz^+) length increases on the riblet surface, indicating that the local friction velocity u_τ is decreased. It is also found that the streamwise persistence of the streaky structures becomes shorter on the drag reducing surface.
2010-10-29