UNSTEADY MASS-TRANSFER IN TURBULENT-FLOW CLOSE TO A ROTATING CYLINDER

Electrodiffusional methods of studying unsteady turbulent mass transfer involved measurement of a transient current characteristic I(tau) after step polarization of a rotating annular cylindrical 46 mm dia electrode at a fixed rotational velocity at Re = (2-9) x 10(4) and Sc = 2.4 x 10(3). The potassium ferri-ferrocyanide system with NaOH background electrolyte was used. An initial asymptote at tau --> 0 served as a test. The similarity of the normalized transfer coefficient K+ = beta/u* with respect to the Reynolds number demonstrated turbulent flow development. Tests were aimed at determining the power n in the approximate law of attenuation of turbulent diffusion D1 in the y-direction normal to the wall D(t)/nu = by+n. A numerical solution of the unsteady turbulent diffusion equation obtained as a set of 1g DELTA(xi) = f(xi) curves for 3 less-than-or-equal-to n less-than-or-equal-to 4 with an interval 0.2, where DELTA(xi) = I(xi)/I(xi)xi --> infinity - 1 has been achieved.