PROPELLER 4402 
y = 10 DEG 
NO SCREEN 
Kerwin (PUF2IS) 
Kerwin & Lee (PUF2) 
O Experiment 
=< 
=. 
_ 
-. 
1000 K(¢.)4 
McCarthy (QUASI) 
— 
0.4 0.5 0.6 07 0.8 0.9 1.0 11 
J=V (1-Wyy)/nD 
Fig. 9 — (Continued) 
which is opposite to the trend of the 
experimental data. Since this is a 
lightly-loaded linear theory, it was 
anticipated that the predicted unsteady 
loading coefficients «(p my1, would be 
essentially independent Off JAN 
earlier version of the unsteady lifting 
surface method developed by Tsakonas and 
his associates (21) at Davidson 
Laboratory, in which the propeller 
helical wake was approximated in a 
staircase manner did predict that the 
periodic loading coefficients ‘(F,m) 
in axial wakes were essentially 
independent of J (17). It is not clear 
why the method of Tsakonas et al (6,7) 
predicts that kp m)1 increases 
substantially with increasing J. 
In general, the predictions by the 
method of Tsakonas et al are closer to 
the experimental results at high advance 
coefficients than they are at low 
advance coefficients. The predicted 
amplitudes are approximately 65 percent 
of the experimental value at design J 
and 30 to 35 percent of the experimental 
values at the lowest values of J 
evaluated. The finding that this method 
predicts periodic loads in inclined flow 
that are significantly less than the 
experimental values is consistent with 
the results presented in References 1 
through 4. 
14 
PROPELLER 4402 
Y =10DEG 
NO SCREEN 
Kerwin (PUF2IS) 
Pex) 
Se 
—eeeconas et al (PPEXACT) 
0.4 0.5 0.6 0.7 0.8 0.9 1.0 11 
J=V (1-Wyypq)/nD 
Fig. 10 — Phases of First Harmonic Blade Loads in Tangential Wakes 
Correlation Between Experiment and Theory 
The unsteady theory of Tsakonas et 
al predicts that the maximum values of 
the loading components will occur at 
approximately 15 to 20 degrees of blade 
angular position before the 
experimentally determined angles; see 
Figure 10. 
The unsteady theory of Kerwin and 
Lee (8) showed, in general, somewhat 
better agreement with experimental data 
over a range of advance coefficient than 
either the quasi-steady method of 
McCarthy or the unsteady method of 
Tsakonas et al. This applies to both 
amplitudes and phases. The trends of 
the predictions of the amplitudes over a 
range of advance coefficients were very 
similiar to the trends of the predic- 
tions by the method of McCarthy. The 
method of Kerwin and Lee underpredicted 
the periodic loads, by approximately 5 
to 20 percent of the experimental 
values, with closer agreement being 
obtained for the Fx and My 
components at the higher values of J. 
The unsteady theory of Kerwin and 
Lee predicts the phases to within 5 to 
15 degrees of the experimental values 
