centrifugal and gravitational loading from hydrodynamic loading. Sup- 

 plemental experiments were conducted to assess the influence of the 

 downstream dynamometer boat on the flow in the propeller plane. These 

 supplemental experiments consisted of wake surveys in the propeller 

 plane in calm water without the hull pitching (Condition 1 in Table 1) 

 with and without the downstream body. These wake surveys yielded a 

 direct measure of the change in the velocity distribution through the 

 propeller disk attributable to the downstream body. 



D. Data Acquisition and Analysis 



Data were collected, stored, and analyzed on-line using a mini- 

 computer. A computer program was written with options for analyzing 

 each of the two basic types of runs: (1) operation in calm water with- 

 out hull pitching, and (2) operating with periodic hull pitching and/or 

 operation in regular waves. Data were collected and analyzed in the 

 same manner as described by Boswell et al. (1976a, 1976b, 1978). For a 

 given run, the computer collected force, moment, propeller rotation 

 speed, model speed, hull pitch angle, and wave height at 4-degree in- 

 crements of propeller angular position over 200 to 300 propeller revo- 

 lutions. 



For operation in calm water without hull pitching, the computer 

 was used to analyze and print the data. The average force and moment 

 signals for each 4-degree angular position were printed along with the 

 average model velocity and propeller rotation speed for the run. The 

 standard deviation of the accumulated data for the run was also calcu- 

 lated for V, n, and the force and moment signals at each position. A 

 harmonic analysis was performed on the force and moment data providing 

 the mean signal and amplitude and phase of the first 16 harmonics of 

 shaft speed. 



For runs simulating hull pitching or waves, the force and moment 

 data were selectively analyzed over the range of pitch angles or wave 

 heights measured. Initially, the values of pitch and wave height were 

 averaged over each revolution of a given run. An analysis was 

 used to search through a series of similar runs extracting propeller 

 revolutions of force and moment data corresponding to prescribed values 

 of pitch or wave height with a prescribed slope and tolerance band. 

 Typically, 50 to 200 revolutions were averaged at each value of pitch or 

 wave height. Twenty-six positions in the pitch or wave cycle were 

 selected for analysis. 



For runs with pitching in waves, both the pitch angle and the wave 

 height were fed into the computer. The blade loading data could be 

 sorted based on either of these two signals. To check the proper phas- 

 ing between the two signals, the pitch and wave data were also analyzed 

 in the time domain. For each run, a strip chart record of the pitch 

 angle and wave height variation was printed, along with analysis of the 

 average frequency, amplitude and phase of the two signals. Runs with 

 consistent wave and pitching frequency, amplitude, and phases were 

 selected for blade loading analysis. 



