364 



1.0 OWL = 28.00 ft 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 60.7 



DWL= 28.00 ft 



Lenqlh on Woterline, 



Desianed 444.0 fl 



Droft.for'd. 20.67 ft ^ 



Droft.Qft 24.50 ft "^'"^ 



Displacement 11,606 1 240 

 Speed for test 17.55 kt 

 Taylor Quotient To , bosed 



on Lpy^L 0.833 



Plane of Surve\j 



IS 6.323 ft ford, of AP 06,ll,08~ 



Third numeral Represents Moqnitude 



of Tanqentiol Component of the 210 



Wahe Velocitv 195 1 [/ ifflo \l ; i65 



Fig. 60.1 Wake-Survey Diagram for Victory Ship, TMB Model 3801, at 11,606 Tons Displacement 



pinwheel provided an adequate number of 

 measurements were made. It would also show a 

 characteristic feature of the presence of a longi- 

 tudinal-axis vortex passing through the disc 

 position of a screw-propeller. This vortex reveals 

 itself by producing what may be called "opposite" 

 transverse-velocity components, along any one 

 radial line within the disc or at any one blade 

 position. One or more of these components may 

 indicate flow meeting the blade in its normal rota- 

 tion while others on the same blade may indicate 

 flow which follows the blade. 



The magnitude of the tangential or rotational 

 incident-velocity components around a circle of 

 radius 72 in a screw-propeller disc, reckoned 

 normal to the blade axis at any blade position, is a 

 rough indication of the amount by which the 



blade is meeting or following the flow at that 

 position. For example, in the diagram of Fig. 

 60.D, for TMB model 3594, the maximum meeting 

 and following effects for an outward-turning 

 propeller occur at 10:30 and at 4:30 o'clock, 

 respectively. For the former, at the intermediate 

 circle on the diagram, the wake fraction is 7.2 

 per cent and the transverse component 15.5 per 

 cent, so that 6 = tan"^ 15.5/(100 — 7.2) = about 

 9.5 deg. The flow is meeting the blade. For the 

 4:30 o'clock position, 6 = tan"' 13.3/(100 - 2.1) 

 = about 7.7 deg. The flow is following the blade. 

 At the 1:30 and 7:30 o'clock positions on that 

 circle, the meeting and following effects are 

 negligible. However, because of the radial com- 

 ponents, the effective velocity over a blade 

 element at 1 :30 o'clock on that circle, with wake 



