초록 |
Turbulent drag reduction (DR) induced by polydispersed high molecular weight calf thymus-DNA (CT-DNA) in a buffer solution under a turbulent flow was performed using a rotating disk apparatus (RDA) and its various characteristics were studied. We also examined the effect of DNA (coil form) concentration on DR efficiency and compared its DR efficiency with the one induced by a water-soluble, linear flexible polymer, poly (acrylamide). It was found that an abrupt change of drag reducing efficiency occurs with an addition of spermidine into turbulent flow due to the transition of DNA conformation. The resultant asymptote DR efficiency explains the origin of those changes, which can be conclusively verified via the electrophoresis experiment. Despite the different flow condition with and without a condensing agent, all CT-DNA molecules possessed the same half-cut dimension, implying the discrete change of DNA conformation can dramatically alter the flow characteristics. |