902 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. X1.2 



Cs — Celerity of an elastic or compression wave 

 in any medium 



Cm — Chord length, mean or average, of a 

 hydrofoil, or of the expanded blade sections of 

 a screw propeller outside the hub 



Cr — Chord length, root, of a cantilevered 

 hydrofoil; also the chord length at midspan of a 

 symmetrical-planform hydrofoil 



Ct — Chord length, tip, of a hydrofoil 



Cx — Distance from the leading edge to the 

 point of maximum thickness of a hydrofoil 

 section, measured parallel to the base chord 



Cz — Distance from the leading edge to the 

 position of maximum camber of the meanline of 

 a hydrofoil section 



C — Cross force, normal to both the direction of 

 motion or resultant liquid flow and the direction 

 of lift 



Ca — Coefficient, Admiralty; the value of the 

 dimensional expression A'''F7P,(or A'^^FVP^), 

 where A is the weight displacement in tons of 

 salt water 



Cb— Coefficient, block, = V/iLB^Hx); alter- 

 native sjmabol 5 (delta) 



Cc — Coefficient, cross-force, = C/{qAL); see 

 NOTE under Cd 



Co— Coefficient, drag, = D/(().5pAUb) = 

 D/{qA) 



NOTE: — In the mathematical expression for this 

 coefficient, as for many others in the list, it is 

 possible to use D and R, U and V interchangeably. 

 It is also possible, for special work, to substitute 

 for A any expression having the same dimensions, 

 such as (BH), L^, B^, and H^, provided this is 

 explicitly stated. The symbol q for ram pressure 

 signifies 0.5pf7j or 0.5pVr . 



Cp — Coefficient, mean or average specific 

 friction drag, = Dp/(qS); see NOTE under Co 



Cj — Coefficient of reduction, of a rudder or 

 control surface; the ratio of the actual torque 

 on a ship rudder stock to the torque calculated 

 for the same rudder angle and relative speed in 

 open water 



Ck — Coefficient, rolling moment, = K/{qAL); 

 see NOTE under Cc 



Ci— Coefficient, Hft, = L/{0.5pAhUb) = 

 L/iqAn); see NOTE under Cd 



Cm — Coefficient, midlength section, = 

 Am/{BmHm); alternative symbol /3(beta) 



Cm — Coefficient, pitching moment, = 

 M/(qAL); see NOTE under Cc 



Cn — Coefficient, yawing moment, = N/{qAL); 

 see NOTE under Co 



Cp — Coefficient, prismatic, longitudinal, = 

 V/(LAx)', alternative symbol 0(phi) 



Cp , Cu — Coefficients, propeller, of D. W. 

 Taylor, dimensional in character. When T is in 

 lb, Q is in Ib-ft, n is in revolutions per sec, and 

 P and D are in ft: 



Cp = 52.889(P/Z))Cg ; 



Crj = 8.4175(P/Z))(1 - S!,)Cr 



[Taylor, D. W., S and P, 1943, p. 101; PNA, 

 1939, Vol. II, p. 141]. 



Co— Coefficient, torque, = Q/(n'Z)'P'). This 

 coefficient is dimensional and is becoming obsolete. 



Ch — Coefficient, residuary drag or resistance, 

 = P«/(?S) = Ct - Cp; see NOTE under C^ 



Cs — Coeffi cient, w etted -surface, dimensionless, 

 = S/VVL = S/VVL 



Ct — Coefficient, total drag or resistance, = 

 Rr/iqS) = Cp + C„ ; see NOTE under Cc . In 

 this particular case, the use of the wetted surface 

 S is arbitrarily taken as the standard; the use of 

 any other value equivalent to (length)^ is covered 

 by a special note. 



Cr— Coefficient, thrust, = T/(n'D^P'). This co- 

 efficient is dimensional and is becoming obsolete. 



Cv — Coefficient, speed, usually of a planing 

 craft, = V/ y/gB; preferably called the &-Froude 

 or beam-Froude number 



Cw — Coefficient, load, of a planing craft, = 

 W/{wB^); the symbol Cld is preferred 



Cw — Coefficient, designed waterplane, = 

 Aw/{LBx); alternative s3Tnbol a (alpha) 



Cx — Coefficient, maximum section, = 

 Ax/{BxHx) 



Cy — Coefficient, relation, = Cp/Cw 



C, — Coefficient, shearing stress, in viscous 

 flow, = r/q 



Cam — -Coefficient, added mass, of entrained 

 water around a body or ship, as related to the 

 ship mass 



Cbd — Coefficient, bilge diagonal; ratio of th e 

 area inside a bilge diagonal to the area [L(BDI)] 



Ccp — Coefficient, center of pressure, for a 

 hydrofoil; ratio of (the distance from the leading 

 edge to CP) to (the chord length c) 



Cdl — Coefficient, dynamic lift, of a planing 

 craft, = W/{qB"-) = 2{C^o)/Cl 



CtL — Coefficient of square moment of area of 

 waterplane for pitch, = /^/[(L'B.0/12] = I^/ 

 (0.083L'B;f) 



CiT — Coefficient of square moment of area of 



