213 



* .T f» V. 7 



FIGURE 7. Body plan of model. 



Also as a reference, the vorticity distribution 

 was measured by the five-hole Pitot tiibe for com- 

 parison with the rotor-type vortexmeter measure- 

 ments 



The positions where the vorticity distribution 

 of the stern vortices was measured, are shown in 

 Table 2 in which sq.st. 1/8 correspond with the 

 section of the propeller disk. The effects of 

 velocities of the model ship are studied at several 

 mesh points. 



In order to discuss the scale effect of the 

 vorticity distribution, the results of measure- 

 ments on both models are shown in Figures 8 and 9 , 

 and the induced velocity vectors on the Y-Z plane 

 which are calculated with the vorticity distribu- 

 tion, are shown in Figures 10 and 11. 



The interval of mesh drawn on both diagrams of 

 vorticity distributions and velocity vectors, 

 corresponds to a non-dimensional length of 0.5% 

 Lpp. The values of equi-vorticity contours in 

 diagrams of vorticity distribution are non- 

 dimensional vortices defined as follows: 



2ttm Lpp 

 X 



U 



(6) 



where co shows the vorticity in r.p.s. which 

 corresponds to twice the number of rotor revolu- 

 tions. Considering a diagram of vorticity dis- 

 tribution as a geographical contour map, the vortex 

 core can be compared to a typical plateau. The 



TABLE 1 Principal Particulars of Models 



Model Ship No. 



M-7 



M-4 



Length (m) : Lpp 7.000 4.000 



Breadth (m) 1.167 0.667 

 Breadth Draft Ratio 2.760 



Block Coefficient 0.802 



Longitudinal Prismatic Coeff. 0.810 



Pitch Ratio (const.) 

 Boss Ratio 

 Expanded Area Ratio 

 Number of Blades 



0.7143 

 0.180 

 0.665 

 5 



TABLE 2 Measurement Positions of Vorticity 

 Distribution 



-^q. St. 

 Model\ 1/2 



1/4 



1/8 



*1 



A *3 



M-7 



M-4 



Port 



Port 



Port *2 

 Starboard 



Port *2 

 Starboard 



Port 



Notes 



*1 Corresponds to propeller position 



*2 Measured by vortexmeter and 5-hole Pitot tube 



*3 Corresponds to Sq.St. -1/8 



fact can clearly be seen in the foreward detections, 

 especially sq.st. 1/2 in Figure 12. In this 

 connection, the vorticity distribution is sq.st. 1/4 

 and A are presented in Figures 13 and 14 

 respectively . 



As a reference, the induced velocity vector 

 diagram on sq.st. 1/4 is shown in Figure 15. 

 Furthermore the vorticity distribution (for 

 M. No. M-7) obtained by the five-hole Pitot tube 

 (diameter 12mm, angle between center and side 



FIGURE 8. Vorticity distribution of M.No.M-7 at 

 Sq.st. 1/8. 



