Nowaeckt and Sharma 
P2) The thrust and torque predictions of the previous step 
are compared with the actual performance as measured in step E2 
and the agreement is improved iteratively by adjusting the assumed 
foil characteristics. Again the crucial link in the algorithm is the 
circulation distribution, 
P 3) Using the Hough and Ordway (1965) approximation, the 
circulation distribution is now translated into an equivalent source 
distribution over the propeller disk. 
P4) This source distribution is the basis for calculating the 
wavemaking due to the propeller by Havelock's (1932) theory. In parti- 
cular, the axial velocities induced by the operation of the propeller 
near the free surface, in other words the self-induced free-surface 
wake of the propeller, can be calculated. 
P5) This self-induced wake is fed back into the propeller 
performance program based on lifting line theory to obtain predictions 
of thrust and torque with the propeller operating at shallow submer- 
gence. 
P 6) A comparison of propeller performance predicted in 
step P5 with actual measurements at the same submergence then pro- 
vides a check on the correct accounting of free surface effects in the 
theoretical model. 
After the mathematical representations of hull and propeller 
have been verified the actual interaction analysis can be executed as 
follows. 
I1) The Froude propulsion factors (mean effective wake, 
thrust deduction, relative rotative efficiency and propeller efficiency 
in the equivalent open water condition) are first determined from the 
results of tests El, E2 and E3 in the usual manner. 
12) The radial distribution of nominal wake from step E4 is 
adjusted to match the mean effective wake from step 11 and fed into 
the propeller performance program, The output is the circulation dis- 
tribution of the propeller in the behind ship condition at each Froude 
number. 
13) Again the Hough and Ordway relation is used to translate 
the circulation distribution into a source representation of the propel- 
ler in the behind-ship self-propulsion condition. 
1850 
