γ-DNA induced turbulent drag reduction and its characteristics

Turbulent drag reduction (DR) induced by monodispersed high molecular weight lambda-DNA in a buffer solution under a turbulent flow was investigated using a rotating disk apparatus. The DR efficiency was maintained over time due to the durability of the lambda-DNA in a moderate turbulent shear flow, and this behavior was compared to a water-soluble linear flexible long chain polyacrylamide (PAAM). To investigate the mechanical degradation mechanism of lambda-DNA, the maximum drag reducing rotation speed (rpm) of the disk was examined by increasing the rotation speed using two different modes to increase the rpm: a continuous and stepwise mode. The mechanical degradation of lambda-DNA with a high turbulent flow was analyzed using an electrophoresis method, which indicated a midpoint scission of the long chain molecules. The DR efficiency at different rotation speeds and results of a long-term experiment also supported the half-length degradation of lambda-DNA and strong resistance of the helically stranded lambda-DNA structure in a turbulent flow compared to its water-soluble flexible counterpart.