360 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 60.6 



bossings, made before and after alterations, are 

 given by F. H. Todd, SNAME, 1949, Figs. 26 and 

 27, p. 234. These and other wake diagrams for the 

 Normandie are published by F. Coqueret and P. 

 Romano in SNAME, 1936, Figs. 1-4 on p. 135 and 

 Figs. 9-10 on p. 139. 



(q) Henschke, W., "Schiffbautechnisehes Handbuch (Ship- 

 building and Ship Design Handbook)," 1952, p. 132. 

 Shows wake diagram for twin screws abaft bossings. 



(r) Van Manen, J. D., Int. Shpbldg. Prog., 1955, Vol. 2, 

 No. 8, pp. 162-163 



(s) Kinoshita, M., and Ikada, S., Int. Shpbldg. Prog., 

 1955, Vol. 2, No. 9, Fig. 7, p. 237. 



60.6 Three-Dimensional Wake-Survey Dia- 

 grams. If ail the wake-velocity vectors are not 

 parallel to the direction of motion but are generally 

 parallel to each other and to one plane which 

 contains the plane of the shaft, there exists what 

 might be called simple non-axial flow. Such a 

 flow might occur at a single-screw position under 

 a wide, flat stern, sloping upward and aft at a 

 nearly constant rate. Non-axial flow then occurs 

 in the vertical plane, corresponding to that in 



diagram 2 of Fig. 17. C. Here, in the 12 o'clock 

 blade position, the actual inflow-velocity magni- 

 tude is U A sec ^(theta) while the effective velocity 

 with respect to a blade element is U a . It is the 

 latter which is measured by a device that records 

 or indicates only the fore-and-aft or direction-of- 

 motion velocity components. For the special case 

 considered, and for the 12 and 6 o'clock blade 

 positions, the instrument indications are valid. 



For other blade positions, however, such as 

 those at or near 3 and 9 o'clock in the special 

 situation considered, there is actually a large 

 increase in incident or resultant velocity and 

 effective angle of attack for the downward moving 

 blade and a large decrease in both for the upward 

 moving blade. Taking account of the induced 

 velocities increases these differences. The fact that 

 the lift varies as the square of the relative velocity 

 at which the blade elements move still further 

 increases the difference. 



Typical 3-diml wake-survey diagrams on ship 

 models, made with the TMB 13-orifice spherical- 



TABLE 60.b — Data Accompanying Wake-Survey Diagrams of Figs. 60.D Through 60.H 

 All tests were made at the David Taylor Model Basin. The Taylor quotients are based on the ship lengths listed. 



For details relating to TMB model 4414 (jwt 4144), see SNAME, 1954, Fig. 5, p. 402; Fig. 7, p. 404; and Fig. 11, p. 409. 

 For those relating to TMB model 3594, see SNAME RD sheet 98. 



