波状壁面上の乱流構造と抗力に及ぼすうねりの影響(流体工学,流体機械)

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Turbulence structure and friction and pressure forces acting on two-dimensional wavy walls with and without swell were numerically investigated. A three-dimensional direct numerical simulation (DNS) based on a finite difference method was applied to turbulent boundary layer over the wavy walls. Two conventional methods for estimating the friction velocity from the loglaw of the mean velocity and the Reynolds stress in the vicinity of the wall were also examined by applying the results of the DNS. The results show that the turbulence intensities, turbulence kinetic energy and the Reynolds stress over the wavy walls are promoted by the swell on the wavy walls. The larger swell makes the friction drag smaller and the pressure drag larger. The total drag increases with the increase of the swell amplitude because of the rapid increase of pressure drag. The results suggest that the reduction on the friction drag by the swell causes the decrease of the mass transfer across the air-water interface with swell as reported in the previous measurements. The friction velocities estimate by the conventional methods increase with the increase of the swell amplitude, whereas the net friction velocity calculated directly from the friction drag is decreased by the swell. This suggests that the friction velocities estimated by the conventional methods do not reflect the friction drag and they are not appropriate parameters for correlating the mass transfer coefficient across the air-water interface with swell.
社団法人日本機械学会の論文
2005-06-25

波状壁面上の乱流構造と抗力に及ぼすうねりの影響(流体工学,流体機械)

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