252 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 52.S 



Fig. 52.R Lines op Flow for Run op Model op 

 S. S. Clairton 



of the surface flow. The details of the chemical 

 methods, some representative results, and in- 

 structions for interpreting the traces are described 

 by J. F. Hutchinson in TMB Report 535, of 

 May 1944, entitled "The Delineation of Surface 

 Lines of Flow and Wave Profiles at the David 

 Taylor Model Basin." Two body plans showing 



TMB Model 3594 5NAME RD Sheet 98 \-0858 F„-0255 



linos of flow are reproduced on pages 6 and 7 of 

 this report. 



Several flowhnes are hkely to come together as 

 they approach the surface, usually between the 

 after quarterpoint and the stern. A case in point 

 is that of the flow along hues E arfd F on TMB 

 model 3898, representing the twin-skeg Manhattan 

 design, depicted in Fig. 52.T [SNAME, 1947, 

 Fig. 24 on p. 116 and Fig. 26 on p. 117]. Here, 

 at Sta. 18.5, the two lines of flow not only join 

 but appear to be about ready to project themselves 

 up through the water surface, just above the 

 junction point. Apparently the two large-size 

 stream tubes along E and F change shape rapidly 

 between Stas. 16, 17, and 18.5, so that opposite 

 the latter point they are both very thin in a 

 girth wise direction and very thick in a direction 

 normal to the hull. The junction point is appar- 

 ently close to the separation point at that girth- 

 wise position, so that abaft Sta. 18.5 the stream 

 tubes in question have gone off and left the hull. 



The following is copied from page 7 of TMB 

 Report 535, referenced earlier in the section: 



"A careful study of the streamlines on the model will 

 afford a fund of information not only as to the direction of 

 flow, but concerning the nature of the flow. A long, narrow 

 line indicates high velocity; a short, wide and smeary line 

 indicates low velocity; a sudden breaking off of the line 

 indicates separation from the surface of the model; and 

 an irregular line or an area with diagonal tails indicates 

 eddying along the model." 



The orthodox lines-of-flow diagrams, such as 

 those in Figs. 52.R, 52.T, and 52.U, show only 

 very mdirectly the dii-ection taken by the water 

 when flowing aft under a ship model, especially 

 if the bottom is flat. Fig. 52. V is a fish-eye view, 



Bow-Wqve Crest at 5ta. 0.9. -o- 0.045 L Abotl FP 



Fig. 52.S Lines op Flow for TMB Model 3594, Representing Minelayer U. S. S. Terror 



