Time-resolved particle image velocimetry(PIV)was used to investigate the flow at suction and pressure sides of 60% span of blades

as well as the flow at the radial plane of fan outlet in a low-speed forward-swept axial fan with three blades at Reynolds number of 370000

based on the tip speed and the blade chord.The data was processed to yield the time evolution of Reynolds shear stress and averaged velocity shear strain using the phase-averaged method

and the spatial phase relationship between the both was investigated through the correlation technology.The phase lag between Reynolds shear stress and averaged velocity shear strain was found

which phenomenon widely existed in the three-dimensional non-equilibrium turbulence.So the studied Reynolds stress-strain lag eddy viscosity model could be considered as a promising closure for improving the state-of-the-art industrial computational fluid dynamics by accounting for non-equilibrium effects in comparison with a classical linear k-ε model

which is widely applied in the industry.