On Some Local Aspects of Turbulent Drag Reducing Flows of Dilute Polymers and Surfactants
Local aspects of turbulent drag reducing flows were studied via evaluating the surrogate dissipation, the third order velocity structure function, the third order moment of the derivative of the velocity fluctuations of a flow in water and in drag reducing solutions (polymer and surfactants) at the same flow conditions. While both the dissipation and the enstrophy production are reduced strongly for both drag reducing flows, they exibit some qualitative differences. Namley, in a polymer solution flow the disispation is increasing with the distance from the wall, whereas it is decrasing for the flow of surfactant solution. The inhibition of enstrophy production is stronger in the near wall region in the polymer solution, while for the surfactant the tendency is opposite. Thus there are clear indications on the qualitative differences in mechanisms in the two drag reducing flows.
KeywordsStructure Function Drag Reduce Inertial Subrange Dilute Polymer Solution Local Aspect
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