Visualization of flow behind the inlet of regular pyramidal diffuser

Adjacent region of L/W=1.0 in the diffuser with 2Θ=10°

Abstract

With the divergence angle increasing, flow begins to be turbulent immediately after passing the inlet of a regular pyramidal diffuser.
In the diffuser having an angle of 2Θ=10°, the increase of turbulence on the dif-fuser axis begins to be suddenly great between L/W=0.5 and 1.0.
The cross section of the diffuser has been visualized usimg the taft method at the position of L/W=1.0 where this turbulence begins to be suddenly great.
On the other hand, measurements have been carried out at the visualized point using hot wire anemometer having I-and conical type probes, and mean velocity and velocity fluctuation distributions have been obtained from it.
From these results, the early stage of occurring turbulence has been investigated and concluded.