The AO-177, first of a new class of Naval Auxiliary Oilers, experienced high levels of inboard airborne noise and initial-stage erosion damage on its skewed, seven-bladed propeller during builder's trails. This report describes the problems, corrective design modifications considered, and procedures and rationale used to develop a successful corrective design modification consisting of a fin to improve the flow into the propeller. To evaluate the problem, extensive model experiments were conducted, including flow visualization, wake survey, powering experiments, and a crucial series of cavitation experiments including propeller-induced hull pressure measurements in a large water tunnel. Experiments with two fin designs showed the superiority of a flow-accelerating configuration. Other experiments showed some benefits of altering the propeller blade shape. Propeller analyses were undertaken to provide design alternatives for retrofitting the ship with a new propeller. A full-scale trail with the final fin design provided evidence or reduction of the highest levels of airborne noise, reduction in the initial-stage erosion damage, and minimal effect on ship speed. The result is that the AO-177 has been accepted by the fleet for normal service. (Author)
Causes and Corrections for Propeller-Excited Airborne Noise on a Naval Auxiliary Oiler
1983
59 pages
Report
No indication
English
Marine Engineering , Noise Pollution & Control , Marine propellers , Propeller noise , Tanker ships , Noise reduction , Airborne , Skewness , Propeller blades , Erosion , Cavitation , Vibration , Damage , Hydrodynamic control surfaces , Fins , Water flow , Acceleration , Model tests , Water tunnels , Naval vessels , Auxiliary , Flow visualization , AO-177 vessel , Skewed propellers , Flow control fins