Trans RINA, Vol 153, Part A1, Intl J Maritime Eng, Jan-Mar 2011 100
20 40 60 80
-40 -30 -20 -10 0 10 20 30 40
-100 -80 -60 -40 -20 0
Heading angle
Figure 10: Propeller disc centre relative to the propeller centre at zero heading angles in different
3.3 EXPERIMENTAL PROCEDURE IN WAVES
The tests in regular waves were carried out using the same
propeller shaft rotational
velocities as in calm-water, corresponding to the 0.0434≤ F n ≤ 0.217 Froude number range and its associated 0.2 ≤
J ≤ 1 propeller advance coefficient range. The propeller heading angle was held at zero degrees for all tests in waves. The model was free to heave and pitch in waves. The range of the propeller blade Reynolds numbers was 0.32 x 106 – 0.35 x 106. The model held course at 0 and 180o into the waves in all wave conditions. The influence of ship motion on the propeller loads was investigated by carrying
out the experiments at different for this wave
amplitudes and frequencies. The applied regular waves are shown in Table 3. Waves were chosen in order to avoid the propeller blade tips coming out of the water during the experiments. Also,
experiments were carried out at the largest model draft. Table 3: The list of regular waves selected for T (s) 2
experiments in wave conditions Name
HS-2s-225mm HS-2s-170mm HS-2s-160mm FS-2s-160mm FS-2s-200mm
2 2 2 2
Height (mm) 225 170 160 160 200
Wave Heading Head Head Head
Following Following
In addition, during the model tests, the ship model speed, propeller speed, incoming wave elevation, ship motion and acceleration in heave, and the model resistance were also measured.
3.4 DISCUSSION OF RESULTS IN WAVES
A typical record of propeller load fluctuation is shown in Figure 11.
Figure 12: Variation of propeller loads for different components.
Generally, the peaks in loads are found when the hull pitch passes through the maximum values (stern-down
reason, the the speeds and advance
Figure 11: Typical record of loads on the propeller fluctuation in waves
A sample of variation of propeller force and moment amplitudes components is
periodic loads are presented versus time. given in Figure 12. The propeller
azimuth positions (Values are presented as a percentage of the propeller radius)
Xp Yp
All the presented results in waves, except Figure 11, are filtered with a low-pass filter with cut-off frequency of 5Hz. Note that
oscillations, seen in Figure 11, is that of the blade. The low frequency
to the wave
frequency. The low-pass filter removes the propeller blade
frequency variations, but encounter frequency response.
the frequency of the higher frequency corresponds
encounter retains the wave
©2011: The Royal Institution of Naval Architects
A- 15
Centre of the propeller disc (Xp/Rp,Yp/Rp)
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