301 



optical laser methods is a promising tool in the 

 research fields of boundary layers and propeller 

 flows . 



The additional investigations on the "Sydney 

 Express" help in full-scale model correlation only 

 slightly; the main purpose of these measurements 

 was the securing and better interpretation of the 

 scattered light results. The following additional 

 measurements were performed: 



1. Propeller-excited pressure fluctuation 

 measurements with six pressure pick-ups above 

 the propeller. 



2. Cavitation observations for determination 



of the thickness and extent of the cavity by 

 means of stereo photography. 



3. Investigations of water-quality by means of 

 a simple scattered light method (Aminco- 

 colorimeter) for detecting suspended particles 

 and total air content by means of a Van-Slyke- 

 apparatus . For both measurements water 

 samples were taken. 



4. Velocity measurements in the control volume 

 of the scattered light measurement in order 

 to estimate the bubble concentration. 



The "Sydney Express" , as one of the fastest 

 German single screw merchant ships, was chosen for 

 the investigations because its propeller has an 

 interesting cavitation extent. 



2. 



SHIP DATA AND PREPARATION OF THE MEASUREMENTS 



installations. For reasons of the ship's safety 

 and also to enable proper cleaning these windows 

 were pushed through 350 mm sluice valves together 

 with their tubular guide pipes. The windows, of 

 which only that opening was marked in Figure 1 

 which had been used for measurements, were arranged 

 between frames 12 and 13. Also, the fitting of the 

 three 350 mm sluice valves required skillful impro- 

 visation on the spot. The installations of the 

 sluice valves for the pressure pick-ups, dimensioned 

 in Figure 1, and of the cavitation observation 

 windows were carried out without any difficulties. 



In addition, all electric lines were laid out 

 from the measuring pick-ups to the measuring con- 

 tainer during this period. The necessary amplifiers, 

 digital magnetic tape recorders, and computer (HP 

 2100 A) with its peripheral equipment were located 

 in this measuring container. The measuring container 

 was located in hole 6 directly on the tank deck of 

 the after peak, in the last bay. For the determi- 

 nation of the performance data of the ship, strain 

 gauges were attached to the shaft. In addition, 

 the shipborne electro-magnetic log (system Plath) 

 for determination of the ship's speed was connected 

 to the computer via an isolation amplifier. Thus, 

 the ship's speed and power could also be recorded 

 at each pressure fluctuation- and LSL-measurement. 

 A recalibration of the log was made on the outward 

 voyage in the North Sea by means of a speed measure- 

 ment carried out by the Hamburg Ship Model Basin 

 using their method with a resistance log. 



The single screw, turbine-driven ship "Sydney Express" 

 has been built by Messrs. Blohm and Voss AG, Hamburg 

 (No. 872) and belongs to the so-called second 

 generation of container ships. 



The main data of the ship are given in Table 1: 



TABLE 1 - "Sydney Express" - Data 



3. 



Propeller Data 



The necessary conversions of the ship construction 

 for the installation of the measuring devices in 

 the after peak of the ship were carried out at the 

 Hapag-Lloyd ship yard at Bremerhaven during the 

 latter part of September 1977. Figure 1 shows 

 allusively to what an extent the narrow steel 

 construction had to be cut free. The installation 

 of three windows for the reception of the scattered 

 laser light proved to be the most complicated of all 



PROPELLER EXCITED PRESSURE FLUCTUATIONS AND 

 CAVITATION OBSERVATIONS 



The measurements of the propeller excited pressure 

 fluctuations were started on the outward voyage 

 when leaving the English Channel and continued until 

 the arrival at Marseille (Tests No. 1-11) . Further 

 details on these measurements as well as for the 

 pressure fluctuation measurements carried out in 

 the Mediterranean (Tests No. 13-16) are given in 

 Tables 2a and 2 b. 



FIGURE 1. Locations of test setups. 



