Huang and von Kerezek 
DISCUSSION 
L. Landweber 
Untverstty of Iowa 
Instttute of Hydraulte Research 
Iowa Ctty, U.S.A. 
Iam very pleased to see such a basic study of viscous cha- 
racteristics of flow about a ship at nonzero Froude number. There 
have been too few such studies. As the authors realise, the method 
that they used to calculate the three-dimensional boundary layer on 
the ship is suitable only for fine formes, free of the cross flows, 
bilge vortices, secondary flows and separation. I hope that, in the 
continuation of their work, they will use methods which are suitable 
for fuller forms, possibly with separation, extending even into the 
thick boundary layer zone near the stern. 
I would like to call attention to a book on three-dimensional 
boundary layers, recently published by one of my colleagues at the 
University of Iowa, V.C. Patel. It is available only directly from 
him ; he is his own publisher. 
Concerning the potential flow, we at the University of lowa 
have tried the technique that is used in this paper, that of Tuck- 
Kerczek, and some of our work on this method was reported at the 
Seventh Symposium in Rome. The method is a very attractive one. It 
appears to enable one to obtain the parametric equations of a ship 
form in a very compact way. Our exprerience has been, however, that 
the method cannot give a sufficiently accurate representation of the 
hull at the bow and stern, so that it could not be useful for obtaining 
source distributions or for calculating wave resistance, especially 
since, for wave resistance, the result is very sensitive to small 
deviations from the original form. It appears, however, that the me- 
thod is suitable for determining the streamlines at low Froude number 
and can serve as the basis for determining a streamline co-ordinate 
system for boundary-layer calculation, as the authors have shown. 
One results in the paper is not clear to me, and may be 
incorrect. On page 10 the authors give a separable form for the po- 
tential function. 
Their assumption is that the free-surface condition can be 
applied below the undisturbed water surface. I think that this result 
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