Abstract:
Frictional losses and near wall turbulence can be reduced in pipelines by addition of small
amount of' high molecular weighi. polymer to water. In the present study experiments were
conducted in a rectangular mixing conduit of an effervescent atomizer to quanti' the effect of
addition of drag reducing agent (DRA) on bubble lhrmation from an orifice in horizontal
cross-flow. Bubble size and its distribution in the midstream of atomizer influence the quality
of spray. f-fence modification of bubble formation after DRA addition can in ttirn have an
effect on the quality of spray. Bubble formation was studied using high speed shadowgraph
imaging techniques. Modification in bubble formation pattern as well as increase in the bubble
size was examined with increase in DRA concentration. Further, Particle Image Velocimetry
(MV) was used to study velocity profiles in the channel at different DRA concentrations in a
single phase flow study in order to examine and verify the role of DRA in modified bubble
formation. Drag reduction was calculated from pressure drop measured using pressure
transducers and a reduction of tip to 60% in the drag was observed. NV measurements
established that there were signilicant changes observed in mean stream wise velocity profile
alier DRA addition and instantaneous velocity fluctuations. Moreover DRA assisted in
reducing span wise velocity fluctuations and Reynolds stress was observed to be zero for the
maximum concentration used during this study. The results were compared with other studies
reported in the literature and were found to be consistent.
