F. = ^AC^^' - pyC^^ (2.3) 



where p = fluid density, A = cross sectional area of armor unit in direction of flow, C^ : 

 drag coefficient, v = peak vertical velocity just above the armor layer as plotted in 

 Figure 2.7, V = armor unit volume, C„ = inertia coefficient, and dv/dt = total fluid 

 acceleration. The drag force, the first term on the right side of Equation 2.3, can be 

 expressed as a function of the armor nominal diameter, D„, by introducing an armor 

 shape factor, K^, as follows 



A = K^D^ (2.4) 



The drag force in Equation 2.3 is then given by 



F^ = pD^C^^v'; C'^ = ^ (2.5) 



where the nominal diameter was previously defined as 



D. = V"' = 



I ^fA 1/3 



where Vr= armor weight and Yr= armor specific weight. 



At the point of maximum vertical fluid velocity, the local vertical fluid 

 acceleration, dvldt, and horizontal velocity, u, are negligible. As such, the total 

 acceleration reduces to a convective term. 



(2.6) 



23 



