Thin ring wing as a means of flow improvement upstream of a propeller

TL;DR

This paper investigates a thin ring-shaped wing as a passive vortex-generator to improve upstream flow for propellers, combining theoretical modeling and towing tank experiments to demonstrate its effectiveness in reducing flow irregularities, vibrations, and noise.

Contribution

It introduces a novel ring-shaped wing device for flow control upstream of propellers, with a linear model and experimental validation showing its potential benefits.

Findings

Theoretical model estimates vortex strength based on flow irregularity and geometry.

Experimental results in towing tank confirm the model's predictions.

Ring-shaped wing effectively reduces flow irregularities and associated vibrations.

Abstract

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.