Study of the three-dimensional flow in a T-junction using a dual-scanning method for three-dimensional scanning-particle-image velocimetry (3-D SPIV)

A three-dimensional, whole-volume, and time-resolving velocity measurement technique is presented and was applied to the study the flow in a T-junction of tubes with a diameter ratio of 1/2.35. This technique uses two scanning light sheets perpendicular to each other and applies digital particle-image velocimetry to three-dimensional scanning-particle-image velocimetry. The results show strong resemblance of the vortical structures to that of a jet in a cross flow. The measurements give enforced hints of vortex breakdown within the vortex system due to the interaction of the jet and the cross flow. As is known from the phenomenon of vortex breakdown in tubes, breakdown is followed by a wake region where, even at low Reynolds numbers, increased mixing is observed because of the stretching and tilting of the vortex lines and their nonlinear interaction. This might also be a source of increased mixing in T-junction flow and cross-flowing jets. (C) Elsevier Science Inc., 1997.