250 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 52.8 



Tq=l.ie 



Shallow-Draft River Steamer 



Fig. 52.0 Lines of Flow fob Shallow-Draft Steamer 



Tq =0.855 



Speciol Ship Type 



Fig. 52. P Lines of Flow for Ship with Under- 

 water Bulges 



drawn. A considerable number of ship types are 

 represented [SNAME, 1907, pp. 1-12, Plates 1-7]. 

 Figs. 52.K through 52. Q are adapted from the 

 diagrams in the reference cited, with the proper 

 r, values shown on each. Table 52.a gives the 

 information presently available on the ships 

 represented by seven models of this group. 



In 1910 Taylor published the hnes-of-flow 

 diagrams for two model series, one apparently for 

 a battleship and the other for a light cruiser of 

 that day, in which the maximum-section coeffi- 

 cient Cx was varied from 0.70 through 1.10 for 

 each group of five [S and P, 1943, Figs. 26-35, 

 p. 25]. Fig. 52. Q is adapted from the Taylor 

 reference by adding the principal hull parameters 

 and coefficients, as well as the speed-length ratios. 



Despite the major differences in form between 

 the two parent models the flow patterns are 

 remarkably similar. 



Since 1910 a great many flow tests have been 

 run on ship models at the Experimental Model 

 Basin and the David Taylor Model Basin but 

 unfortunately only a few of the lines-of-flow 

 diagrams have been published in unclassified 

 EMB and TMB reports and the technical 

 hterature. Figs. 52.R and 52. S are copied from 

 two unpublished diagrams. Fig. 52.T is a repro- 



duction, for ready reference, of one such diagram 

 previously pubhshed. 



The Swedish State Shipbuilding Experimental 

 Tank makes use of the wet-paint technique for 

 depicting flowlines around selected portions of 

 ship models [SSPA Rep. 32, 1954, Figs. 18 and 

 19, pp. 26-27]. For the local areas covered they 

 are excellent. A. F. Lindblad includes photo- 

 graphs of flowlines around the bulb bow of a 

 model made mth this technique [SSPA, Rep. 8, 

 1948, Figs. 15 and 17, pp. 18-19]. Published with 

 them is a model body plan upon which a number 

 of flowlines are indicated. 



In 1947 R. Brard and J. Bleuzen published 

 photographs of models in which flowlines were 

 determined during steering tests [ATM A, 1947, 

 Figs. 10, 11, 12, and 13, between pp. 332-335; 

 TMB Transl. 248]. H. F. Nordstrom published 

 similar photographs of the flow near the bow- 

 propeller position on an icebreaker model [SSPA, 

 Rep. 20, 1952]. 



In his book "Marine Propulsion Devices," 

 pubhshed at Leningrad and Moscow in 1949, 

 V. M. Lavrent'ev shows body plans on pages 65 

 and 66 with fines of flow drawn over them. 



A multitude of photographs have hkewise 

 been made of EMB and TMB models with the 

 flow traces marked on them, but only a few 

 are available for study by marine architects 

 [SNAME, 1947, Fig. 9 on p. 104; Figs. 25, 26, 

 and 27 on pp. 116-117]. Lines-of-flow traces for 

 a few selected locations appear on SNAME RD 

 sheets 114 and 115. It is hoped that, in the future, 

 these can be shown on all such sheets when the 

 data are available. 



Fig. 52.U gives a rather comprehensive flow 

 pattern for the transom-stern ABC ship huU 

 worked out in Chap. 66. Figs. 78. C and 78. D are 

 photographs of the model showing the nature 

 and positions of some of the flow traces. 



52.8 Analysis of Model Surface-Flow Dia- 

 grams. The method of analyzing photographs 

 and diagrams of flow fines and flow patterns 

 taken directly on the surface of a model depends 

 upon the technique employed in tracing the flow. 

 Wet-paint streaks are usually short but if the 

 paint fines are closely spaced in a fore-and-aft 

 direction they may be combined fike the short 

 vectors that form path fines, described in Sec. 

 1.4 of Volume I. The traces left by chemicals 

 ejected from orifices in the hull are much longer, 

 sometimes half the length of the model. They 

 may be assumed to give a better representation 



