•J8 



IIM)R()|)N \ WIK.S IN Mill' DKSIGN 



Srr. 12.11 



the Surfaoc of the Ship ami its 1;iT«mI mi lu^isi- 

 anco" ill Paper 789, presented before the World 

 Engineering Congress in Tokyo in 1929. The 

 complete paper is published in the Proceedings 

 of this Congress, Vol. XXIX, Part 1, issued in 

 Tokyo in 1931. The text in question is found on 

 pages 293-318; Figs. 1 througli 30, accompanying 

 the paper, are published on pages 319-341. 



These experimenters rneasureil the distribution 

 of pressure on tlie Inill and the magnitude of the 

 thrust at the tiirust bearing on a self-propelled 

 steel steam launch having a length between 

 perpendiculars of 39.37 ft, an extreme beam of 

 9.79 ft, and a depth of 5.7-i ft. The draft was 

 about 3.99 ft, the trim was zero, and the depth of 

 water for the test with the underwater propeller 

 varied from 12.8 ft to 13.8 ft. 



The total number of pressure orifices was 289, 

 well distributed over the entire length of the 

 launch. Each orifice had a diameter of 1 mm 

 (0.04 in), and was connected by flexible tubing 

 to one glass tube of a multiple-tube manometer 

 which was photographed during the tests. How- 

 ever, it was found that those orifices lying above 

 and in the vicinity of the actual wave profile 

 when underway could not be used. 



The speed of the launch was measured bj' a 

 pressure speed log in the form of a standard pitot 

 tube mounted forward of the bow, with its orifice 

 2.23 ft below the at-rest waterline and about 2.83 

 ft forward of the stem. 



The launch could be driven by its own single, 

 3-l)laded screw propeller or the underwater 

 propeller could be removed and the launch be 

 pushed by an engine-driven airscrew mounted 

 above the deck. A d^'iiamometer served to record 

 the thrust in each case. 



Attempts were made to photograph the wave 

 profile from another boat running alongside but 

 the actual wave-surface inter.section at the IniU 

 was partly oiwcured by the wave crests beyond 

 the hull. The wave profiles given in the report are 

 thase recorded in a model basin on a one-third 

 scale model of the launch. 



Tables accompanying the report give the 

 individual pressure readings for a scries of several 

 Hpeed.s. 



42.11 Pressure Distribution Along a Vee 

 Entrance. The pre.s.sure coeflicients for 2-diml 

 flow along two flat plates, disposed .s3'mmetrically 

 in V-fuithion in a stream, like those on each side 

 of the stem of a shij), have been calculated an<l 

 plot led by II. I'lOU.sc and .1. S. MrXowii. Tlir 



HMilts, dirive<I by conformal transformation on 

 the bai>is that the flow leaves the trailing edges 

 of the plates tangentiallj-, are shown in their paper 

 "Cavitation and Pressure Distribution: Head 

 Forms at Zero Angle of Yaw" [State Univ. of 

 Iowa, Studies in Eng'g., Bull. 32, 1948, pp. 2C-28). 

 These data, supplemented by J. S. McXown for 

 iticluded angles of the order of those encountered 

 on actual ships, are diagrammed in Fig. 42. G. 



10 0.9 Q8 a? 0.6 05 a^ as Qz ai 



Kio. 12.0 Orapiis of Pressure Coefficient for 



luiOAi, I,ujun> Fi.ow Ai-ONO A Two-Dimensional 



\'i;e Entii.\nce 



The varialiuii ol' A/j </ iVdiii the vertex aft serves 

 as an indication of the pressure distribution along 

 the forward portion of the entrance of a simple 

 ship, about as far aft as the forward neutral point. 

 It is expected that these data may eventually 

 be combined with others, possibly those derived 

 from the Guilioton method, for a prediction or 

 determination of the pressure distribution along 

 the 2-(linil waterline area of a ship hull of normal 

 design. 



This i)roblem is (rcaU'd iiy L. M. .Milne- 

 Thomson (TH, 1950, pp. 309-310), who obtains 

 an exi)rcssion for the drag on the pair of plates, 

 with a cavity behind them. H. I.anib [HD, 194'), 

 l)p. 104-10")) describes the analytic solutions of 

 Rethy and HobylelT, of 1879-1881, and gives a 

 convenient table of pressure ratios for this system 

 for entrance slopes from In 170 dcj:;. 



42.12 Use of Doubly Refracting Solutions for 

 Flow Studies. I<\' ii lOMiiiiiiatinn of ]>oiari/,(Ml 



