910 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. XI .2 



5l — Thickness of the laminar sublayer of a 



viscous boundary layer 



Sat — Angle, neutral, of a control surface 



Sp — Angle, diving plane or horizontal control 



surface, with reference to body or ship axis 

 8r — Angle, rudder, Avith reference to ship axis 

 8 s — Angle, stern plane, with reference to ship 



axis 



6* (delta star) — 'Displacement thickness of a 



boundary layer, 



=/:(-f) 



A(delta, small capital) — ^An increment or decre- 

 ment; see also the combination symbols Usted 

 under the letter D 



ACp (using small capital delta) — Increment of 

 specific friction resistance due to surface roughness 

 and other factors 



A (delta, large capital) — Displacement weight 

 or scale weight, in tons of salt water (see item 

 following) ; gravity load on the water for a planing 

 craft 



A/(0.010L)' or A/(L/100)'— Displacement- 

 length quotient of D. W. Taylor for salt water 

 having a sp.gr. of 1.024 at 59 deg F or 15 deg C, 

 equivalent to 63.863 lb per ft' or 35.075 ft' per 

 ton of 2,240 lb, and for a length L in ft; this is 

 dimensional and is equal to the displacement, in 

 English long tons, of a geometrically similar ship 

 100 ft long 



V (pronounced vol) — Volume; displacement vol- 

 ume of a body or ship; alternative symbol V (also 

 pronounced vol) 



Vb — Volume, bulk; alternative symbol Vb 



€(epsilon) — Angle of downwash or sidewash 

 6 — Drag-lift ratio of a blade section or hydrofoil 



f (zeta) — Slope of the surface of a gravity wave, 

 reckoned with respect to the horizontal 



r)(eta) — Angle, vertical path, between the hori- 

 zontal plane and the velocity vector of the motion 

 of the CG of a ship 



7) — Efficiency, general 



■q — Elevation, surface, of a wave, with reference 

 to a plane, usually the still-water level 



Vb , Ve — Efficiency, propeller, behind ship = 

 VoVr 



rio — Efficiency, gearing 



77„— Efficiency, hull, = (1 - 0/(1 - w) = 

 Pe/Pt 



T], — Efficiency, ideal 



riK — Efficiency, ideal, with jet rotation 



7/m — Efficiency, mechanical 



7)0 — Efficiency, propeller, in open Avater, = 

 {Kr/Ka)[J/{2T)] = (r„7„)/(2,m„Qo) 



r]p — Efficiency, propulsive = Ps/Pp = VoVhtir 



■qji — Efficiency, relative rotative, = vb/vo = 

 Vb/vo 



97 s — Efficiency, shafting 



0(theta) — An angle in general 



6 — Angle of pitch or trim in a ship, with refer- 

 ence to the designed or normal attitude in the 

 fore-and-aft plane. Its natural tangent is the 

 algebraic difference of the changes in elevation of 

 the designed waterline at the end perpendiculars, 

 divided by the length L. 



6 — Momentum thickness of boundary layer 



Jo c/-\ uj 



Br — Slope, with reference to the ship center- 

 plane, of the incident flow on a contra-rudder 



ds — Slope, with reference to the ship center- 

 plane, of the median line of a contra-guide skeg 

 ending 



K(kappa) — Coefficient of kinematic capillarity 

 = k/p, where k is the constant of capillarity 



K — Goldstein factor in propeller design, to 

 take account of the number of blades 



X (lambda) — Angle, leeway, or of leeway 



X, J p.hB — Coefficient, absolute advance, = V a./ 



{imD) = VE/irnD) 

 X — Ratio, linear or scale, full-size body or ship 



to model, generally expressed as a number greater 



than unity; for example, 20th scale or 1 :20 model; 



alternative symbol a (alpha) 



;u(mu) — Magnification factor in resonant motion 

 n — Strength of a doublet, or close-coupled 



source and sink 



IX — Viscosity, coefficient of dynamic, = 



r{i2M)/{dU/dy) 



j'(nu) — Kinematic viscosity, coefficient of, = 

 m/p 



l(ksi) — Angle, tab, with reference to the control 

 surface on which it is mounted 



p(rho) — Mass density, or mass per unit volume, 



= m/¥ = w/g 



o-(sigma) — Cavitation index, = (pAba ~ ^)/l 

 cn — Cavitation index based on angular velocity, 

 for propeller tests, = (pAb, — e)/{0.5pn'D'') 

 <ru , <Tv — Cavitation index based on liquid 



