The flow behaviors in T-jets reactors are experimentally studied for a Reynolds number (Re) range of 21-4642. The flow behaviors in T-jets reactors are investigated by a flow visualization technique, and the images of the smoke-seeded flow are captured by a planar particle imaging velocimetry (PIV) and a high-speed camera. The effects of the jet Reynolds number and the geometry parameters on the flow behaviors in T-jets reactors are investigated and discussed. A half deflecting oscillation behavior in T-jets reactor is observed for the first time, whose dimensionless period is about half of that of the unconstrained opposed jets. The critical parameters of the onset of the half deflecting oscillation, e.g., the jet Reynolds number, the normalized jet separation and the width-to-height ratio of jets are obtained. Results show that the jet Reynolds number, the jet separation, the width-to-height ratio of jets, the depth between the front and back walls and the headspace above the injectors of the chamber have effects on the half deflecting oscillation. (C) 2014 Elsevier Ltd. All rights reserved.