Variation of wall shear stress and periodic oscillations induced in the right-angle branch during laminar steady flow

We report on flow phenomena such as wall shear stress and periodic oscillations that occur in the right-angle branch during laminar steady flow in the upstream trunk. The side-branch bifurcates from the trunk at a 90-deg angle, and both the upstream and the downstream corners of the entrance of the side-branch are square-edged. As the flow approaches the entrance of the side-branch through the trunk, the wall shear stress steeply increases along the near wall, and this stress at the upstream corner is comparable to that generated around the flow divider. Periodic velocity oscillations occur downstream in the separation region in the side-branch. The Strouhal number based on the flow conditions in the side-branch is independent of the flow division ratio for the side-branch radii ranging from 4 to 9 mm. Furthermore, it appears that the Strouhal number is weakly dependent on the Reynolds number. The periodic oscillation in the side-branch exhibits a characteristic flow behavior, which is a universally recognized phenomenon in the right-angle branch.