EFFECT OF POLYMER ON DRAG REDUCTION IN A SUDDEN ENLARGEMENT CONFIGURATION

The purpose of the present paper is to study experimentally the effect of drag reducing polymers on losses due to friction and sudden enlargement of pipe cross section. Polymers used in this research include copolymer of acrylamaide with a cationic acid ACA and sodium carboxymethyl cellulose CMC. Two different geometeries were considered, a sudden enlargement in pipe idameter a from 27 mm to 40.5 mm diameter ratio DR of 1: 1.75, and b from 27 to 54 mm DR = 1 : 2. The effect of Reynolds number change, polymer type, polymer concentration, and area ratio were studied. The upstream Reynolds number was varied from 5.1 x l0^4 to 10^5 and polymer concentration from 3 to 32 ppm inside the test section. The experimentalresults showed that the percent drag reduction increases with increasing both Reynolds number and polymer concentration. Drag reduction up to 63.47 % was obtained at 5.1 x l0^4 Reynolds with 32 ppm of ACA in upstream side and drag reduction reappears in downstream side when it was large in the upstream side. While CMC was not effective when used as a drag reducing agent in this range of concentration. Moreover, the sudden enlargement factor was decreased by 18 % when using 32 ppm of ACA at 5 x10^4 Reynolds number. Also, using ACA as a drag reducing agent enhances pressure distribution in the upstream and downstream pipe flow.