van Manen, Oosterveld and Witte 



Fig. 10 - Body plans and propeller arrangements 

 for the 90,000-TDW tanker model 



The model with Hogner-type stern has been tested with three different noz- 

 zles. Nozzle No. 1 is derived from nozzle No. 19a by taking into account the ef- 

 fect of the hub shape of the flow. The taper of the hub is accounted for by locat- 

 ing the nozzle profile with reference to the direction of the undisturbed flow. 

 The direction can be determined if one assumes frictional effects and static 

 pressure variations to be negligible over the axial distance of the nozzle. It is 

 then a matter of satisfying the law of continuity. This method is only permitted 

 if the shape and the diameter of the hub are not too extreme. The design calcu- 

 lations for the ducted screw propeller were based on the method given in Refs. 

 9 and 10. The nozzles No. 2 and No. 3 have in comparison with nozzle No. 1, a 

 more pronounced converging part before the screw. This may be attractive 

 from a viewpoint of a more homogeneous flow in the nozzle. The particulars of 

 the nozzle profiles Nos. 1, 2, and 3 are given in Fig. 12. 



Model resistance and self-propulsion tests were conducted in the deep- 

 water basin in accordance with established procedures. All model data were 

 extrapolated to the full-scale ship values using Schoenherr's friction coefficients 

 with an addition of 0.00035 for correlation allowances. A trip wire of 1 mm 

 diameter, was fitted around each model at station 5 percent LBP for turbulence 

 stimulation. The results of the resistance and self-propulsion tests in the 

 loaded and in the light condition are given in Tables 4 and 5. 



250 



