Sec. X1.2 



SYMBOLS AND THEIR TITLES 



907 



r, R — A radius in general 



R — Resistance, as a force, opposing motion in 

 a liquid; alternative D for drag 



Z2„ — Reynolds number in general, = UL/v = 

 Vhlv 



Rb — Reynolds number for propeller-blade sec- 

 tions where the velocity term is the nominal 

 liquid velocity past the blade section and the 

 space term is the expanded chord length at 0.7R. 

 Here FBUd, = {Vl + [2Tn{0.7R)f\''' and 



R, = [(Co.7ie)(FB,.ae)]/''. 



Rj — d-Reynolds number, with the diameter or 

 width D as the space term, = UD/v = VD/v 



i?i — x-Reynolds number, with distance x abaft 

 the leading edge as the space term, = Ux/v = Vx/v 



Rs — 5-Reynolds number, with boundary-layer 

 thickness 5 (delta) as the space term, = U8/v = 

 VS/v 



Re — Radius of curvature of path or turning 

 circle 



Rf — Resistance to motion, friction 



Rh — Radius, hydraulic, of a channel; the area 

 of liquid in a transverse plane divided by the 

 wetted perimeter 



Rj — Resistance, ideal, of a model run at the 

 ship self -propulsion point, = Rt — D, 



Rp — Resistance, pressure, due to forces acting 

 normal to a surface 



Rr — Resistance, residuary, = Rt — Rf 



Rs — Orbit radius of the circular motion of a 

 surface particle in a gravity wave 



Rs — Resistance, separation 



Rt — Resistance, total, of a body or ship to 

 motion; the sum of the friction, pressure, separa- 

 tion, and all other types of resistance due to 

 relative liquid motion 



Rw — Resistance due to gravity wavemaking 



^wind — Resistance, wind; the axial component 

 of the force exerted by the relative wind on a 

 body or ship, along its a;-axis; to be distinguished 

 from the downwind drag Dw 



Rso — Radius of the rolling circle of a trochoidal 

 wave 



RsA — Resistance, still-air; the wind resistance 

 due to ship speed alone through still air 



s— Space or distance in general, along a 

 straight line or curved arc 



s — Specific gravity of a liquid, non-dimensional, 

 represented by the ratio { [Weight (or mass) of a 

 given volume of the Kquid]/ [Weight (or mass) of 

 the same volume of pure water] } 



Sa — Slip ratio, apparent, = 1 — [V/{nP)] 



Sr — Slip ratio, real or true, = 1 — [F^/(n/-')] = 

 1 - [V,/{nP)] 



As — Equipotential-line spacing, equal to An, 

 measured in the direction of liquid motion 



S — Surface area in general; surface, wetted 



S — Velocity, discharge, of stack or exhaust gases 



S„ — Strouhal number, in general 



Si — Z-Strouhal number, based upon length L 

 as the significant dimension, = fL/U, where / 

 is the frequency of eddies shed behind a body 

 and forming a vortex street or trail 



Sj — d-Strouhal number, based upon diameter 

 D as the significant dimension, = fD/U 



Sb — Surface, wetted, surrounding the bulk 

 volume of a body or ship 



S/ VAL — Wetted-surface coeflBcient of D. W. 

 Taylor, where A is the weight displacement in 

 tons of salt water, as defined under A/(0.010L)^; 

 the sam e as Cws 



S/y/VL — Wetted-surface coeflScient, non-di- 

 mensional; the same as Cs 



S/F'^'— Wetted-surface to (volume'^') ratio 



t — Temperature in general 



t — Terminal ratio of D. W. Taylor, as applied 

 to the shape of a section-area curve; see ts and tg 



t — Thickness in general; thickness of an airfoil 

 or hydrofoil section 



<— Thrust-deduction fraction, = (T - Rt)/T 



t — Time in general 



Ie — Terminal ratio of D. W. Taylor, as applied 

 to the section-area curve at the FP [S and P, 

 1943, p. 65] 



ta — Thickness of a screw-propeller blade, pro- 

 jected to the shaft axis; see SNAME Tech. and 

 Res. Bull. 1-13, 1953, p. 22 



ifl— Terminal ratio of D. W. Taylor, as applied 

 to the section-area curve at the AP, in the same 

 manner as for ts 



tx — Maximum thickness of any selected hydro- 

 foil section 



r— Draft of a floating body or ship; alternative 

 symbols H and d 



T — Thrust; usually ahead thrust; specifically, 

 thrust developed by a propulsion device 



T — Time or period of a complete cycle; natural 

 period of oscillatory ship motion of any kind 



T,— Taylor quotient, = V/ VL, where F is in 

 kt and L in ft; this is dimensional 



J' (pronounced toll)— Towline tension in general 



¥^ , Ty , ¥, — Components of towline tension 

 relative to the x-, y-, and z-axes, respectively, of 

 a body or ship 



