横断方向速度変動に対する波数域を限定した操作による壁乱流の抵抗低減に関する数値実験(流体工学,流体機械)

概要

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We applied the direct numerical simulation (DNS) to study a principle of drag reduction by attenuating the spanwise fluctuation in near wall region. A simple forcing model was introduced into the Navier-Stokes equation to represent the spanwise drag. Such a drag was applied in particular wave-number space to search the most efficient scale for the operation. The friction drag was effectively reduced when the forcing was given in the wave-number region including streak spacing. However, we could not narrow the range to realize the most effective drag-reduction, because the wall-normal component of turbulence energy grew in the uncontrolled scale. Our result suggested that the manipulation on a particular scale was not effective, but it is necessary to restrain the spanwise fluctuation over a certain spatial scale to achieve the drag-reduction.
2004-12-25