Method and apparatus for increasing the effectiveness and efficiency of multiple boundary layer control techniques

This invention relates to a much more efficient method and apparatus to reduce the drag of plates or vessels moving relative to a fluid and of internal flows such as liquids moving through marine water-jet propulsors. The invention can be used to eject additives into specific regions of the boundary layer to modify the rheological properties of the fluid without the undesirable disruption of the boundary layer and without the rapid diffusion of the additive across the boundary layer inherent in traditional ejection techniques. 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.