Turbulent flows of solutions of surface-active substances

Abstract

Not only polymers, but also some surface-active substances have the capacity to reduce the hydrodynamic resistance in the turbulent regime of a fluid. From the point of view of stability against mechanical destruction, the addition of surface-active substances has certain advantages over polymers; in particular, they are capable of recovering their hydrodynamic effectiveness having passed through pumps and local points of resistance [1]. The basic possibility of reducing drag by the addition of surface-active substances was demonstrated in [2–6]. It was later shown that a reduction in the drag of liquids could be achieved only by micelle-forming surface-active substances [5, 7], in solutions of which spherical and platelike micelles, respectively, are formed at the critical concentrationsCm1 andCm2 for micelle formation. The values ofCm1 andCm2 depend both on the molecular structure of the surface-active substances as well as on external factors such as the temperature, the presence in the solution of electrolytes, polar organic substances, and so forth. The connection established in [5, 7] between the reduction in the drag and the value ofCm2 suggests that the reduction in the turbulent friction will also depend on the above factors. It is therefore possible to control processes of turbulent transfer in a fluid as well as the drag. However, this possibility has not been sufficiently studied. In [1–7], the influence of surface-active substances on the drag was investigated. First data on the velocity profiles in solutions of surface-active substances were given in [9, 10]; they are not sufficiently complete. In the present work, we made measurements of the velocity profiles and the turbulence intensity in solutions of surfaceactive substances, and we have calculated the generation of turbulence energy and the dissipation of the energy of the averaged motion. We have studied the influence of electrolytes and the temperature on the reduction in the drag and give the results of full-scale experiments.