The pulseless injection of polymeric additives into near-wall flow and perspectives of drag reduction

Abstract

The analysis of experimental data reveals that the polymer consumption is connected with the ship velocity by linear dependence, and that the fuel economy is connected by the cube one. That is why, the velocity range of the profitable use of polymer additives can exist theoretically always. Now, at the existing consumption of polymer injected as a jet through slots into near-wall region, and since polymer is significantly more expensive, than fuel for the present, application of polymer additives can be profitable only of short duration in the high velocity sea transport. For example, “polymeric forcing” allows to increase load-carrying capacity for hydrofoil craft of type “Kometa” of 50% to help to engine at the going out from a water and to use their total power in the cruiser regime of motion. The problem of studies is increase of specific effectiveness Ψ/q, which is the main parameter determining a profit. Ψ/q is a ratio of drag reduction to dimensionless coefficient of polymer consumption. For the present, Ψ/q < 4·10⁷. Calculations lead to the conclusion that from the point of view of profit it is worth while not to tend to the drag minimization, but to restrict the friction reduction twice. The tests with the wash-out of coatings give the value Ψ/q = 3·10⁸ (for Ψ ≃ 0.2). The drag reduction method by polymer additives will be profitable at an application for the most part of types of the sea ships at the realization of the given specific effectiveness. Calculations and tests testify the ways of the specific effectiveness increase are the polymer molecular mass increase, preparation of injected solutions and the pulseless injection.