Abstract: A method for increasing the efficiency of additive drag reduction by establishing a drag-reducing viscoelastic coating on a surface. The method includes mixing a polymer into a concentrated solution that has approximately the same density as a fluid flowing over the surface, ejecting the mixture/solution into the flowing fluid in a manner such that a coating of polymer, which initially grows thicker with time, is adsorbed onto the surface, and reducing the ejection rate of the first fluid such that the coating of polymer then grows thinner with time. These steps may be repeated so that a desired minimum coating thickness is maintained over an extended period of time. The method reduces the polymer expenditure rate for a given drag reduction. Moreover, the produced viscoelastic coating impedes the attachment and growth of drag-producing natural organisms and may be applied without “down-time” (e.g., while underway).

Abstract: A method for increasing the efficiency of additive drag reduction by establishing a drag-reducing viscoelastic coating on a surface. The method includes mixing a polymer into a concentrated solution that has approximately the same density as a fluid flowing over the surface, ejecting the mixture/solution into the flowing fluid in a manner such that a coating of polymer, which initially grows thicker with time, is adsorbed onto the surface, and reducing the ejection rate of the first fluid such that the coating of polymer then grows thinner with time. These steps may be repeated so that a desired minimum coating thickness is maintained over an extended period of time. The method reduces the polymer expenditure rate for a given drag reduction. Moreover, the produced viscoelastic coating impedes the attachment and growth of drag-producing natural organisms and may be applied without “down-time” (e.g., while underway).

Abstract: In an apparatus and method for ejecting an additive for significantly reducing the drag of a first fluid moving relative to a wall, a drag-reducing substance is conditioned by causing a second fluid, which includes the drag-reducing substance as a dispersed solid, liquid or gas, to flow through a nozzle. The second fluid is then passed by a vortex chamber prior to ejection of the second fluid into the first fluid via an aperture that includes a Coanda surface on a portion thereof. Additional techniques are also disclosed which increase the effectiveness and efficiency of ejecting a drag-reducing substance into a fluid that is moving relative to a wall, and which thus enable multiple layers to be established without the undesirable disruption of the boundary layer and without the rapid diffusion of the additives across the boundary layer that occur in prior art ejection techniques.