A New Appraisal of Strip Theory 



2. Properties of Fluid 



Density 

 Viscosity 

 Surface tension 

 Elasticity 

 Vapor pressure 

 Pressure 



Also thermal, electric, magnetic properties, etc. 



3. Relative Motion Parameters 



Orientation parameters: x^,y^,z^,0,q),\lj,h . 



Dynamic parameters: u,v,w,p,q, r,u,v, w,p,q, f,h,h . 



For a surface ship of fixed geometry, mass and mass distribution moving 

 at constant speed in a sufficiently idealized fluid, the total force and moment 

 depend only on the parameters describing the relative motion between the body 

 and the fluid. For pitch and heave motions of a surface ship, these are: 



a. Body and fluid orientation parameters : z^^.ei.h. 



b. Body and fluid dynamic parameters : w, q,h,w, q,h. 



The most convenient way of defining an unknown function is in terms of its 

 multivariable Taylor expansion about some convenient equilibrium point. Since 

 we will be content with developing a linear theory, only the linear terms in the 

 expansion need be retained. A convenient equilibrium point about which to ex- 

 pand the total force and moment and hence their components z and M is that 

 characterized by: (a) constant ahead speed, u = u^ , and (b) zero orientation 

 and dynamic parameters. The Taylor expansions for the heaving and pitchii^ 

 forces then result in: 



« = ».,(h,h.h,t) . (f) (.-.,J . (f) («-«„) . (f) (w-w„, 



o 



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