Langmuir probes and a Mach probe were used for measuring edge fluctuations
and parallel plasma flow, respectively, on the CT-GB tokamak, A maximum rad
ial gradient in parallel flow was observed to be located roughly at the max
imum E-tau shear layer (or, namely, the poloidal velocity shear layer). E-t
au. shear is found to be very possibly consistent with a regulating effect
on edge turbulence features. Non-linear analysis indicates that non-linear
phase coupling in turbulence may be influenced by E-tau shear, or that ther
e exist coherent structures induced by strong E-tau shear, and the phase co
upling processes show an intermittent character. The results provide some n
ew observations for a better understanding of the basic mechanisms of edge
turbulence.