Nowaekt and Sharma 
It is seen that our relative rotative efficiencies always come out less 
than unity, irrespective of whether nominal or effective wakes are 
used for analysis. The above numbers cannot be used as evidence 
either for or against Telfer's hypothesis. However, our paper con- 
tains more specific information not explicitly pointed up in the text. 
Since our computer simulation of the propeller behind the hull includ- 
ed the radially varying circumferentially averaged axial wake com- 
ponent but none of the other nonuniformities, its results may be used 
to isolate what may be termed for brevity the "rvcaaw'' factor from 
all the other influences responsible for relative rotative efficiency. 
This is done in the following table ( see below ), It is seen that the 
"rvcaaw'' factor, represented by the ratio of open-water torque K 
to the simulated torque Koy in a hypothetical flow in which only a 
radial variation of the axial wake is allowed, is here indeed slightly 
Computer simulated Rakes eat 
behind-hull condition 7 
5 625 01 
676 
larger than unity, while the remaining factors nevertheless lead to 
an exceptionally low overall relative rotative efficiency of our model. 
However, we recall that Beveridge (1963a) by a different numerical 
procedure obtained values of 0.94 (in a submarine hull wake) and 
1.01 (in a ship hull wake) for the "rvcaaw'' factors of two wake- 
adapted propellers. Hence the question, whether or not a radially vary- 
ing (but circumferentially uniform) axial wake can be blamed for 
spuriously large values of relative rotative efficiency as argued by 
Telfer (1951), must be regarded as still open. 
In reply to Professor Telfer's next comment, we do not want 
to argue whether the wave component of wake should be attributed tc 
the presence of the free surface or to the waves on the free surface. 
The fact is that any finite disturbance moving at or near the free sur- 
face will cause waves and hence wave wake, In particular, a propeller 
moving near the otherwise undisturbed free surface will also cause 
waves even in the absence of a hull and thus experience a wave wake ; 
1956 
