正方形断面90°ベンド内における界面活性剤水溶液の遷移状態での二次流れの発達(流体工学,流体機械)

抄録

The separation and secondary flow of surfactant solution with shear-thinning viscosity, in a square-sectioned 90° bend, has been investigated by measurements of velocity field using PIV and wall pressure distribution at the same bulk velocity, when Reynolds number is 45000 in the solvent (water). The surfactant solutions run with the transition state from the laminar to the turbulent. The shear-thinning viscosity is represented by power-law parameters, n and K. It is shown that the secondary flow and separation of manistream flow occurs at the upstream location in the bend as the pseudo-plastic viscosity K increases. For the downstream location, the intensity of secondary flow is so decreased that the mainstream runs through the larger radius of curvature. The existence of optimum shear-thinning viscosity, which induces the minimum intensity of secondary flow, is found. That means the detection of the critical profile in the transition state. The increase of pressure gradient in the radial direction at the upstream enhances the intensity of the secondary flow.