CAVITATION OF PROPELLERS IN NOZZLE-RUDDERS--INFLUENCE OF RUDDER ANGLE

The Authors, of the El Pardo experiment tank, discuss the advantages of the nozzle-rudder for trawlers and other vessels whose propellers are submitted to heavy loads, point out the need for careful design of the duct/propeller system so as to avoid the excitation of hull vibration, and briefly review theoretical treatments of cavitation and associated phenomena inside the duct. The paper is then mainly concerned with a model investigation, at El Pardo, on severe vibration experienced in the stern of the trawler Urabian (3,000 tons displacement) when her nozzle-rudder angle exceeded 20 deg. during sea trials. The investigation is described, and the results, including diagrams of observations made during tests in the cavitation tunnel, are presented and discussed. It was found that propeller cavitation increased with helm angle, and before this reached 35 deg. there was severe vibration, noise, and serious erosion of the propeller and duct. The fundamental characteristics of the cavitation was its instability. Some further conclusions are drawn, and it is mentioned that El Pardo has for some time recommended, and the present investigation has confirmed, the nozzle-rudder angle should never exceed 20 deg.; this angle would produce at least the same turning effect as the 35 deg. of a conventional rudder. Order form BSRA as No. 48,994.

  • Supplemental Notes:
    • This paper was presented at the 15th Sesiones Tecnicas de Ingenieria Naval, held in Palma de Mallorca in June 1977.
  • Corporate Authors:

    Asociacion de Ingenieros Navales

    Apdo Correos 457
    Madrid,   Spain 
  • Authors:
    • Baena, JLC
    • Basnez, JFN
    • Hidalgo, J M
  • Publication Date: 1978-1

Language

  • Spanish

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00182531
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Oct 12 1978 12:00AM