V.G.Pogrebnyak, A.A.Pisarenko Solution of polymers in conditions of near-the-wall turbulence and the mechanism of hydrodynamic drag reduction |
Applied hydromechanics, Vol. 2 (74) ¹ 2, (2000) |
| The considered experimental data of polarizatin- optical study of wall turbulence of polymer solutions reducing turbulent friction give a convincing confirmation of a strong deformation effect of a hydrodynamic field on macromolecules under wall turbulence. The obtained results support the idea that the mechanism of drag reduction is uniquely related to the process of complete unrolling of macromolecules which cause nonlinear elasticity effects. Velocity and velocity gradient fields arising at the entrance of a small capillary during the free-converging flow (in conditions of near-the-wall turbulence) of aqueous solution of polyethyleneoxide, as well as the degree of the coil-stretch transition of the macromolecule were experimentally studied. The hydrodynamic field arising under the converging flow conditions resulted in a considerable (60%) degree of polymer stretching which, in turn, led to a readjustment of the hydrodynamic field itself. Is established, that regularities of macromolecular in case behaviour of a current with a longitudinal gradient of speed and the effects of elastic deformations have the greatest value for understanding the nature "anomalous" (from the point of view of classical hydromechanics) phenomena - Toms' effect. |
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| TEXT LANGUAGE: Russian |