Sec. 52.14 



FLOW PATTERNS AROUND SHIPS 



257 



Numbers ot Sides Indicate Positions of 

 Wove Profiles and Flow Traces at 

 Those Stations 



U.S. Maritime Commission Desii 

 T2-5E-AI 

 TMB Model 3867 

 BALLAST CONDITION 

 Trim, IZft b\j theStern 



Fig. 52. Xb Lines of Flow in Ballast Condition for U. S. Maritime Commission Design T2-SE-A1 



With a broad, blunt bulb as a waterline begin- 

 ning, at light draft, the bow-wave crest may be 

 surprisingly high, although the upper portion of 

 the crest is more apparent than real, in the form 

 of a bow feather. 



Whether the sections at the forward end of the 

 entrance are sharply flared outward or are of the 

 bulb type, the Bowlines will undoubtedly curve 

 and pass under the ship very close abaft the stem. 

 This means, for one thing, that air entrained in 

 the bow-wave crest may be expected to flow 

 along under the bottom at transverse distances 

 rather close to the centerhne. 



Figs. 52.Xa and 52.Xb indicate the differences 

 in wave profile and flow pattern found on two 

 model tests of a tanker. In the light condition the 

 displacement is less than half the full-load dis- 

 placement, and the trim by the stern is very large. 



52.14 Predicting Velocity and Pressure Dis- 

 tribution Aroiuid Ship Forms. If the magnitudes, 

 direction, and distribution of velocity and pressure 

 are to be calculated by the methods discussed in 

 Chap. 50, this prediction will be for a hull form 

 which has the shape of the physical ship plus the 

 displacement thickness of the boundary layer, as 

 nearly as the latter can be determined. If the 

 velocity and pressure factors are to be predicted 



on the basis of empirical data, the fund of inform- 

 ation presently available must be greatly ex- 

 panded. It now comprises the references listed 

 in Sec. 52.12 plus the following: 



(1) Eggert, E. F., "Form Resistance Experiments," 



SNAME, 1935, pp. 139-150 



(2) Eggert, E. F., "Further Form Resistance Experi- 



ments," SNAME, 1939, pp. 303-330 



(3) Yokota, S., Yamamoto, T., Shigemitsu, A., and 



Togino, S. ; see Sec. 52.3 for the complete listing 



(4) Izubuchi, T., full-scale experiments on the Japanese 



destroyer Yudachi, Zosen Kiokai, December 1934, 

 Vol. 55; English translation available in Research 

 and Development Division, Bureau of Ships, U. S. 

 Navy Department 



(5) Hiraga, Y., "Experimental Investigations on the 



Resistance of Long Planks and Ships," See. Nav. 

 Arch., Japan, 1934. 



Fig. 52.Y is a reproduction of one of the after- 

 body plans of EMB model 3383 from (2) preceding 

 [SNAME, 1939, Fig. 30 on p. 314]. It carries the 

 isobars for a multitude of Ap values, as indicated 

 in the diagram. 



A comprehensive measurement of pressure 

 around the surface of a ship or model is a pro- 

 digious undertaking, yet anything less than 

 comprehensive is not worth the effort, from the 



