Van Oortmerssen 



DISCUSSION 



J. P. Breslin 



Stevens Institute of Technology 

 Hoboken 3 New Jersey 3 U.S.A. 



It is very comforting to find that measurements and calcula- 

 tions for the forces and pressure distribution on the cylinder having 

 a diameter equal to the wavelength are so well correlated, but I sup- 

 pose this is not surprising for short waves. I wonder if the author 

 would comment on the comparison of the measurements and calcula- 

 tions for longer wave lengths where viscous effects may be expected 

 to be important. 



A second question : there was some information provided on 

 the interference between two cylinders. Would the author let us know 

 how this could be compared with theory as the cylinder spacing is in- 

 creased ? 



REPLY TO DISCUSSION 



G. van Oortmerssen 



Netherlands Ship Model Basin 

 Wageningen, Netherlands 



On the first question, we have indeed results for longer waves 

 and in that case the agreement is even better, but for the longer waves 

 especially when the wavelength is longer than about five times the body 

 dimensions, we can use approximative methods which give the same 

 results and are much simpler to handle. So I think our computer pro- 

 gramme is only of interest for the relatively shorter waves. 



On the second question, about the interference of two cylin- 

 ders, we have indeed performed measurements. We measured the 

 wave force on cylinders for different spacing s of the neighbour cylin- 

 ders, for different wavelengths and for different wave directions, and 



1000 



