Propeller Excitation and Response of 230000 TDW Tankers 



as shown in Figure 1, and new full scale measurements of vibrations 

 and pressure fluctuations were carried out |_2J . The results of these 

 measurements were promising. The pressure fluctuations, as well 

 as the noise and vibration levels, were lower. Further the service re- 

 ports confirmed the results of the model tests, indicating no increase 

 of the power consumption. The problem of erosion of the propeller 

 blades was, however, not solved, although some improvement could 

 be noticed. 



The main modification applied to the second ship was that fins 

 (somewhat different from those of the first ship, see Figure l) were 

 fitted during construction. In addition, a six-bladed propeller was 

 fitted, having a radial load distribution different from the original 

 five-bladed design. 



Successful trials were carried out with this ship |_3 J . Further, 

 the new propeller has so far worked without any trouble. 



II. SCOPE OF THE PRESENT INVESTIGATION 



When the project work was completed it was felt that, if com- 

 plementary model tests and full scale measurements could be carried 

 out with the second ship, an opportunity had arisen to obtain unique 

 material showing the influence of different modifications on the model 

 as well as on the full scale, whereby investigations concerning the 

 correlation factors for propulsion, vibratory response and cavitation 

 could be made. 



Accordingly a research program was established, which was 

 carried out in close cooperation between Uddevallavarvet, SSPA and 

 DnV. 



Together with the investigations carried out on the first ship 

 the full scale program included : 



1. Speed trials with measurements of propeller thrust and thrust 

 variations (second ship only) 



2. Photographing of cavitation patterns at different propeller loadings 

 and angular blade positions (second ship only) 



3. Inspection of the propellers with regard to cavitation erosion 



4. Measurement of propeller induced hull pressure variations 



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