The velocity fields in the circular tube with trapezoid-winglets inserted were investigated by particle image velocimetry (PIV) technique and the turbulent characteristics induced by different arrangement winglets were also compared. The results showed that swirling flow induced by the up-flow winglets extent along the radial direction and had greater intensity as well as better persistence. Inside vortex pair the flow was to the wall direction while outer vortex pair the flow was away from the tube wall

which flow pattern was inversed for the down-flow winglets. In addition

the swirling flow induced by down-flow winglets extent more along the circumference direction and the disturbance effect was obvious in a short distance downstream the winglets. Both swirling flow patterns could disturb the near wall region flow

destroying the velocity boundary layer and notably improving the velocity component normal to the mainstream

which lead to the intensification of the transverse mixing action and mass transfer in the tube. As the Reynolds number increasing

the dissipative interaction between the two flow layers was enhanced

decreasing the stability of longitudinal vortex. In a certain range of Reynolds numbers involved in the experiment

it could be drawn that both arrangement winglets showed better disturbance effect when Re=3000.