260 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 52.18 



Scot, and Scot. Shipbldrs. Assoc, 1865-1866, 

 Vol. IX, pp. 52-64]. By suspending over the stern 

 of a small sci'ew-propelled vessel a flat swinging 

 vane with an indicator he measured "the aiigle 

 of the water driven off from the screw" with 

 reference to the centerplane. The vane was raised 

 and lowered to cover a range of positions from 

 0.285R to 0.8R below the axis. The data given 

 below are for a propeller radius of approximately 

 0.8R. By turning the vane in a direction normal 

 to the current at its axis and measuring the 

 moment on the vane Rigg was also able to obtain 

 a rough idea of the actual velocity at each of the 



measuring stations. For three conditions of 

 operation he recorded the following data: 



(1) The vessel propelling itself only, at 144 rpm; 

 35 deg, 2.1 psi 



(2) Towdng a large "flat," with cargo, at 160 rpm; 

 45 deg, 1.0 psi 



(3) WhUe moored to a post at 136 rpm; 72.5 deg, 

 0.4 psi. 



Other published data on the distinctive features 

 of the outflow jets of marine propellers have so 

 far not been discovered. Some unpublished data 

 from the tests of two model propellers at the 



Estimated .ocu5 of \ ?^^ ° '^"^f' 

 Centers of Lonqfd'l I ^"'^ ^°^'^'°" 

 Vortex m Propeller | °^ Propelle- 



0.61 D A baft I Fore-$n d-Aft Position of 

 Disc Position I Lonqitudinal Center of 

 of Propeller Propeller 



Equivalent to True Velocity Vector 



0.28 V H Lies at an 



. -I 0.28 

 "" l.00-(-Q29) 



Fig. 52. Za Diagrams Indicating Components op Net Augmented Axial and Rotational Velocities in Outflow 

 Jet op Port Propeller on TMB Model 3613' 



Transverse Vector Component; 

 are Drawn to Twice the Scale 

 of V^ and the Wake 

 Vectors 



Wake Measurements 

 Available on 

 Starboard Side Only 



Fig. 52.Zb Diagrams Indicating Axial and Rotational Components op Velocity in the Outflow Jet op 

 EMB Propeller 857, Running in Open Water 



