\m 



HVHROnYNAMICS IN SHIP DESIGN 



Srr. 41.12 



acuUil ill tliat rcfiTi'iiio l>y llu> syii»l>ol p iiisteml 

 of by the R'STS or I'lTC symbol w. 



A nitlior comprohonsivo <liscussion of steady 

 flow ill pij)«'.s aiiil eoiuliiit.-^, from tlie slnndpoiiit of 

 hyil ran lies ami hydrixlynamies, is given by V. L. 

 Strcetor in Cluip. VI of "EngineeriiiR Hydraulics" 

 (Rouse, H., Kditor. ia")(), pp. 3S7-1 t.'^j. 



45.12 Computation of the Wetted Surface of a 

 Ship, .\ithough the et)mputation of tiie wetted 

 surface ^' of the unilerwater body of a shij) is a 

 problem in solid geometry rather than in hydro- 

 dynamics, the flow conditions over dilTcrent 

 portions of that surface are closed- related to the 

 specific friction resistance coofiicients. The wetted- 

 surface calculations are therefore made with 

 these conditions clearly in mind. Furthermore, a 

 value of S is required in the earlj' stages of the 

 preliminary design, as described in Sec. 66.9, 

 when the lines may not yet be sketched and 

 there arc no girths to measure. 



D. W. Taylor solved this problem by the use 

 of a wettod-vsurface coefficient, now known as 

 CVs , ba.sed upon data from a great number of 

 models and man.v types of lines, not limited to 

 the series bearing his name. When only the di.s- 

 placement A(delta; large capital), the maximmn- 



s«'ctioii ((K'nirient ('x , the beam-draft ratio B, II, 

 and the "mean immersed length" L were known, 

 the wettinl siirfaee .S was determine*! by 

 i^ = ChsvAL, where A wa.s in long tons 

 (2,240 lb) of salt water of sp. gr. 1.024, with a 

 volume density of .■}.").07.j ft' per long ton. Since 

 the mean immersed length was usually not known 

 until the form was laid out, the waterline length 

 was often substituted for it. 



Contours of C,rx on a basis of C'.v and B/II 

 were first published by Taylor in the 1910 edition 

 of S and P (Vol. I, p. 47; Vol. II, Fig. 41]. They 

 were repeated in the 1933 edition of S and P, 

 Fig. 20, page 20, and in PNA, 1939, Vol. I, Fig. 33, 

 page 90. 



These contours were reworked by M. E. Fowler 

 of the TMB staff in the early 1940's to include 

 data from many additional models of all types. 

 Fig. 20 on page 22 of the 1943 edition of S and P, 

 embodj'ing the revised contours, thus differs 

 slightly from its predecessors. 



As C„s is a dimensional (luaiitity, which varies 

 with the system of measurement, 1). W. Taylor's 

 formula is for this book converted to the 0-diml 

 form 



S = Cs ■ 



CsVVL (-Jo.vii) 



Ratio of Bx/Hx 

 1.0 1.5 



Framed Area is Reproduced to Lorqe Scole 

 2.0 2.5 3 3.5 '-^ij.O 4.5 



1 Ficj 45.H 

 5.0 5.5 



0.701 



1.0 1.5 2 2.5 Z>.0 3 5 4.0 4 5 50 5 5 



Beom-Droft Ratio Bx/Hx 



Km. •l.'i.li Co.NTOUiUH l)K ()-l)lMI. WK-rTKI>-.S|lKKArB CoKI'riCIICNT (\ Kill .Sllll'S 



6.0 



