4. Estimate the object buoyant weight, W^ , the object mass, m, 

 the added mass, c, and the specific drag coefficient, D^ ,_ ^^An') 

 The latter two terms may be estimated for such objects as '^ 2 * 

 submarines through consultation with marine architects. If no estimate 

 is possible, c may be assumed equal to zero and D equal to b with 



no great loss in accuracy. 2 



V 



o 



5. The entry velocity, v , if not known, should be estimated. 



■^ o 



6. A value of time increment. At, for use in the finite difference 

 evaluation should be established. An increment of .01 second was 



used in the analysis of the penetration tests presented in this report. 



7. The Force, F, acting on the object at any depth, x, is 

 calculated according to the equation 



X 



F = + W, - D v^ - Zl c (0 A (£) (19) 



D s s e 



where Si = x -E, 



c ( = soil strength as a function of C 



A (£) = effective area coefficient for zone l - -r— to £ + -r— 

 e 2 2 



the summation is carried out at increments of £ and ? equal to A£. 

 The calculation proceeds as follows: 



a. The force corresponding to the initial velocity and zero 

 embedment depth is calculated using Equation 19. 



b. The entry acceleration, a, is calculated as 



m + c 



c. The velocity and embedment depth at the end of one time 

 increment At are calculated using the relations: 



^At = ^o "^ ^^' 





, ^At + ^o 



A t O 9 



. At 



(20) 

 (21) 



d. The force corresponding to the new embedment depth and 

 velocity is calculated (Equation 19) . 



e. The new acceleration is calculated. 



21 



