矩形ダクト流における局在乱流構造の成長過程

抄録

Spatial growth of transient turbulence in rectangular-duct flow for the cross-sectional aspect ratio As = 3, 5, 7 is measured experimentally by using a multi-PIV (Particle Image Velocimetry) system. As an indicator of the spatial growth, we estimate the area and its growth rate along the duct axis for transient turbulence on the duct midplane. The comparison of the growth rates for As = 3, 5, 7 shows that the growth for As = 3 exhibits a different feature from the others. For As = 5, 7 an equilibrium state of turbulence is observed only at a specific value of the Reynolds number Re, while for As = 3 an equilibrium state is observed in a finite range of Re.