The unsteady flow field downstream of axial-flow turbine
rotors at low Reynolds numbers was investigated experimentally
using hot-wire probes. Reynolds number, based on rotor exit
velocity and rotor chord length Reout,RT, was
varied from 3.2×104 to 12.8×104 at intervals of
1.0×104 by changing the flow velocity of the wind
tunnel. The time-averaged and time-dependent distributions of
velocity and turbulence intensity were analyzed to determine the
effect of Reynolds number. The reduction of Reynolds number had a
marked influence on the turbine flow field. The regions of high
turbulence intensity due to the wake and the secondary vortices
were increased dramatically with the decreasing Reynolds number. The
periodic fluctuation of the flow due to rotor-stator interaction
also increased with the decreasing Reynolds number. The
energy-dissipation thickness of the rotor midspan wake at the low
Reynolds number Reout,RT=3.2×104 was 1.5
times larger than that at the high Reynolds number Reout,RT=12.8×104. The curve of the −0.2 power of the
Reynolds number agreed with the measured energy-dissipation
thickness at higher Reynolds numbers. However, the curve of the
−0.4 power law fitted more closely than the curve of the −0.2
power law at lower Reynolds numbers below 6.4×104.
