Title: Propeller and Rudder in Off-Design Conditions
Abstract:As soon as a vessel does not operate in calm waters but under the influence of wind, waves and current, the vessel can drift and the operating conditions deviate from the so called (single) design poi...As soon as a vessel does not operate in calm waters but under the influence of wind, waves and current, the vessel can drift and the operating conditions deviate from the so called (single) design point, normally obtained during the design stage. Under these circumstances the ship as well as propeller and manoeuvring devices will operate in off- design conditions for long term. This paper summarizes the essential results of investigations done in this respect at HSVA for the national joint research project Off-Design (2012). By means of propulsion tests and wake measurements at straight course and under drift conditions some representative operating points were identified, defining the off-design conditions of a RoRo ferry. Propeller and rudder were then investigated in the cavitation tunnel in these conditions. Off-design propeller pitch settings were investigated as well. By means of pressure pulse and cavitation inception test results the propeller characteristics are compared between straight course and drift conditions. Rudder force measurements show the consequences from the rudder point of view. All the evaluations are based on model tests performed at HSVA. The ship model represents a RoRo ferry designed to operate in the North Sea between Netherland and Ireland. Its particulars are found in the appendix. The influence of the environmental condition onto the ship has been investigated at design draught with load varied propulsion tests under the Computerized Planar Motion Carriage (CPMC). Systematic variations of drift angles (-10°,-4°,0°,4°,10°), propeller pitch angles (design pitch E, E-10.5°, E-5°), propeller speeds n, rudder angles and ship speeds Vs (13kts, 16kts, 19kts) have been investigated. The obtained results represent only possible ship reactions onto variable environmental conditions from the ship side of view. Only the combination with external forces due to imposed environmental conditions leads to the unique equilibrium condition of the ship represented by drift angle β, rudder angle δ and propeller revolutions n. The environmental conditions are defined by wind and wave loads depending on wind states BFT 0/3/6 at encounter angles e between 0° and 360° (=0° headwind, 180° following wind).Read More
Publication Year: 2013
Publication Date: 2013-01-01
Language: en
Type: article
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Cited By Count: 1
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