Thin ring wing as a means of flow improvement upstream of a propeller
This addresses propeller vibration and noise issues in marine or aerospace applications, but appears incremental as it builds on existing vortex-generator methods.
The paper tackled the problem of reducing propeller-induced vibration and noise by using a thin ring-shaped wing as a passive vortex-generator to control flow irregularity upstream of the propeller. It solved the theoretical model for this device and confirmed its effectiveness through experiments in a towing tank, showing good concordance.
There are numerous devices currently known with the purpose of reducing the irregularity of the flow upstream of the propeller and to decrease by that means the propeller-induced vibration and noise. Many of these devices are wing-shaped vortex-generators that affect the flow with their induced (i.e. passive) longitudinal vortices. The paper's subject is the use of a ring-shaped wing as a highly effective passive vortex-generator which allows to 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 a linear approach and the intensity of the induced longitudinal vortices as a function 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.