Flow Field Characteristics in T-Junction Pipes Under the Deflected Jet Conditions During Rolling Motion

Abstract During maritime rolling conditions, the rolling motion generates periodic additional inertia forces, which can result in stronger pulsations of the flow field inside T-junctions. This study, based on PIV (particle image velocimetry) visualization experiments, examines the instantaneous, time-averaged, and pulsation characteristics of the flow field in T-junction channels under both static and rolling conditions. The flowrate ratio between the main and branch pipes is R = 4, indicating a deflected jet, and the rolling Reynolds number ranges from Rer = 0–2640. Under rolling motions, the tangential additional inertia force affects the streamwise velocity (Vx), while the radial additional inertial force affects the normal velocity (Vy). The normal velocity is more significantly impacted, with the fluctuation amplitude of Vy,rms* being about three times higher than that of Vx,rms* at Rer = 2640 at the no-mixing upstream region. Compared with static conditions, the fluctuation amplitude of instantaneous velocity in the branch pipe increases by 2–3.2 times with higher Rer. The instantaneous vorticity transforms between the leading edge vortex (LEV) and the trailing edge vortex (TEV), completing the cycle of vortex generation and shedding. Notably, the vorticity of the LEV is lower than that of the TEV. As Rer increases, the average velocity and vorticity decrease, while the root-mean-square (RMS) of velocity rises at x/D = 0.25, with the RMS of velocity peaking near the inlet of the branch jet along the shear layer.