Some aspects of the flows behind lobed forced mixers

Flow visualization studies have been conducted using the smoke-wire and laser-sheet techniques to examine the flows behind lobed forced mixers of different trailing edge configurations (a square wave, a semi-circular wave and a triangular wave) at a matched velocity ratio across the lobe. The size of the wake region and the strength of the secondary flow shed by a lobe were found to be larger with lobe geometry consisting of straight parallel sidewalls. Formation of streamwise vortices were observed within the first four wavelengths downstream of the trailing edge in the square and semi-circular lobed mixers and these vortices were largely responsible for intense mixing at the corresponding locations. Similar observation was not found in the case of triangular lobed mixer. More importantly, no indication of vortex breakdown was found within seven wavelengths downstream of the trailing edge in the three cases. © 1994.