c;ilAl' 1 I'.R 1 



Force, Moment, and Flow Data for Hydrofoils 

 and Equivalent Forms 



41.1 General; Scope of Chapter 72 



■14.2 Formulas for CnlculafinR Circulation, Lift, 



Drag, ami (Hhor Factors 72 



44.3 Test Data from Typical Simple Airfoils and 



Hydrofoilii 73 



44.4 rolar Diagrams for Simple Hydrofoils . . . 75 



44 . 5 Test Data from Compound Hydrofoils . . 75 



44.6 Flow Patterns Around Typical Hydrofoils . 78 



44.7 Pitching Moment; Ccntcr-of-Prcssure Loca- 



tion 80 



44.8 Distribution of Velocity and Pressure on a 



Hydrofoil 80 



44.9 Velocity and Pressure Fields Around a 



Hydrofoil 82 



44.10 Spanw-iso Distribution of Circulation and 



Lift 83 



44 11 Effective Aspect Ratio for Equivalent Ship 



Hydrofoils 83 



44.12 Design Notes and Drag Data on Hydrofoil 



Planforms and Sections 83 



44.13 Quantitative Data on Cascade and Inter- 



ference Effects 84 



44.1 General; Scope of Chapter. I'lu' hyilro- 

 foils ami 0(|iiivaleiit foini.s for wliich pi'rfonnaiu'o 

 data are k'vcii in this chapter embrace plates and 

 bodies, irrespective of shape or size, which are 

 intendi'il for the production of dynamic lift wlien 

 submerged in a lit|uid. The manner of producing 

 this lift, in a ilircctioii generally at right angles to 

 the flow or to the direction of body motion, is 

 described in Chap. 14. 



Insofar as their behavior is concerned, including 

 test and performance data on them, airfoils may 



Nomenclature and 

 found in: 



■!\'inl)ols for hvdrofoils are 



(a) Sec. 14.2 and the accompanying Fig. 14. .\ 



(b) Sees. 32.8 and 32.9 and the accompanying 

 Figs. 32.F, 32.G, and 32.11 on the geometry of 

 the screw propeller 



(c) Sees. 3r).2, 37.2, and 37.3 and the accompany- 

 ing Figs. 37.A, 37. B, 37.C, and 37.D on fi.xed 

 and movable appendages. 



44.2 Formulas for Calculating Circulation, Lift, 



1)6 classed as hydrofoils if it is known that the Drag, and Other Factors. There are no simple 



flow around the two, in air and water, is generally formulas wliirli will permit the computation of 



similar. In other words, data from tests in air are lift, ilrag, pitching moment, ami other factors on 



perfectly valid for applii'ation to the design and hydrofoils of given shape and on botlies of random 



performance of hydrofoils in water if it is known shape acting as hyilrofoils. There are given here 



that air-water surface effects and cavitation are only a few of the basic fornuilas and procedures 



to 1)6 nonexistent. As a rule, sejiaration effects for the calculation and prediction t)f tlicse quan- 



around botlies wholly submerged in air and in titles. In practice it is necessary to rely on experi- 



water are similar; this applies also to the correla- mental data for the determination of design and 



lion of the.se effects between niiKlel and full scale, other factors. The volume of these data is now 



Since whole books are insufficient to list the very large; some of the priiici|)al sources are listed 



airfoil and hydrofoil data presently available in Sec. 44.3 following. 



(195.")) for design purpases, it is manifestly impo.s- As is customary for groups of fornuilas relating 



sible, in this chapter, to do more than to present to other fields, the shape, characleristics, and 



certain data which the marine architect may find performance of hydrofoils and e(|uivalent bodies 



uwful in ship and appendage ilesign. The.se and an' given in 0-diml ratios, coellicients, and 



other data in the technical literature almost expressions. 



invariably a|)ply to steady-stnte con<litions. For The lift force L developed on unit span of a 



control .surfaces and other ship parts restMubling hydrofoil or similar bod^' in a lii|uid stn-am, when 



hydrofoils, the relative .speeds and angles of circulation is .set uj) by an effective angle of attack 



uttuek may change violently with time. or other suit.able means, is represenleil by 



72 



