Sec. 42.2 



POTENTIAL-FLOW PATTERNS 



TABLE 42.b— (Continued) 



35 



through XXIII, Figs. 1 through 23]. These 

 observations, still valid and useful after nearly 

 six decades, were made at relatively low Reynolds 

 numbers, at least at relatively low stream veloc- 

 ities. 



In Figs. 8 and 9 on Plate XXI of the Hele- 

 Shaw 1897 reference there is shown the flow 

 past a small 2-diml boat-shaped body with a 

 rectangular projection on one side, like the 

 paddlebox of a sidewheel ship totally immersed 

 in a liquid. In one figure the flow is from forward 

 to aft; in the other figure from aft to forward. 

 The diagrams illustrate remarkably well the 

 t3^e of flow to be expected around small rec- 

 tangular projections on a rough surface. Fig. 13 

 on Plate XXII shows the flow around a 2-diml 

 body of lenticular form with a trailing-edge flap 

 set at an angle of about 75 deg. The flow lines in 

 the photograph illustrate clearly the manner in 

 which circulation about the body (a concept 

 unknown at that time) affects the general direc- 

 tions of flow ahead of and abaft the body. 



The report of these experiments was followed 

 shortly by a second report [Hele-Shaw, H. S., 

 "Investigation of the Nature of Surface Resist- 

 ance of Water and of Stream-line Motion under 

 Certain Experimental Conditions: Second Paper," 

 INA, 1898, Vol. 40, pp. 21-46, also Plates VII 

 through XVII, Figs. 1 through 58]. Among the 

 multitude of illustrations in this second report: 



(a) Fig. 7 of the reference shows the upstream 

 portion of a vortex street behind a 2-diml bar of 

 rectangular section placed with its long dimension 

 across the flow 



(b) The photographs of Fig. 21 of the report, and 

 those following, are beautiful pictures of 2-diml 

 flow patterns around cylinders, semi-cylinders, 

 inclined plates, rectangular bars, and strut sections 



(c) Figs. 43 and 44 show the flow around a Taylor 

 ship-shaped stream form 



(d) Figs. 45 and 46 show the flow pattern around 

 a 2-diml model with three pairs of saw teeth along 

 its sides 



(e) Figs. 24, 29, 30, and 32 are remarkable pictures 

 of flow patterns around and between sources and 

 sinks. 



Within the next decade, F. Ahlborn photo- 

 graphed many flow patterns around 2-diml bodies 

 of varied shapes, using sawdust suspended in the 

 water as a motion indicator instead of the alumi- 

 num powder later sprinkled on the water surface. 

 From these photographs and from his observa- 

 tions Ahlborn drew sketches and line diagrams 

 illustrating the principal features of the various 

 flow patterns, with their streamlines, path Unes, 

 and so on. These photographs and flow diagrams 

 are published in the papers: 



(1) "Hydrodynamische Experimentaluntersuch- 

 ungen (Experimental Researches in Hydrody- 



