Turbulent jets of dilute polymer solutions

Abstract

In the present paper, the effect of high-molecular drag reducing polymer additive on free and impinging turbulent jets has been examined. The measurements of radial and axial distributions of the mean velocity of a turbulent jet issuing from a convergent conical nozzle indicate a decrease of the half-width spreading coefficient and the velocity decay rate with an increasing polymer concentration. In the wall jet region the pressure gradients disappear faster than for water though a transition from a laminar to a turbulent boundary layer takes place at a greater distance from the stagnation point. A skin friction drag reduction of about 80 percent, in the range of polymer concentrations of 25–100 ppm by weight, has been observed. The responsible mechanism that has been proposed is the expansion and orientation of polymers in rotation-free straining flows.