The Thin Ring Wing as a Means of Flow Improvement Upstream a Propeller

There are numerous devices currently known with the purpose to reduce the irregularity of the flow upstream the propeller and lo decrease by that means the propeller-induced vibration and noise. Many of these devices are wing-shaped vertex-generators that affect the flow with their induced (i.e. passive) longitudinal vertices. The subject of the paper is the use of a ring-shaped wing as a highly effective passive vertex-generator which allows lo control the flow closer to the most charged sections of · propeller blades. The problem of a thin ring-shaped wing with irregular ( asymmetric) geometry in the irregular steady flow has been solved in linear approach and the intensity of the induced longitudinal vertices as a junction of the irregularity of the flow and the geometry of the ring wing has been estimated using that solution. Experiments in the towing tank showing good concordance with the theoretical model confirmed the effectiveness of such a device. Some additional advantages of a ring-shaped wing incorporated into the construction of stabilizers are considered.