^^^^=^"=^- 



Evaluation of the behavior during free-fall would seek to minimize 

 all instabilities of the anchor during free-fall, including even slight 

 pitching motions, if possible. This evaluation is best carried out by 

 testing models of sufficient size so as to have a drag coefficient equal 

 to that of the prototj^pe. Prelinsinary information indicates that a 

 model 1 m in diameter, giving a scaling ratio of 1:30, will provide that 

 equality. The drag coefficient for the anchor in free-fall is known to 

 be a constant for Reynolds numbers between 10 and 10 (1-m-diameter 



model), and it is expected to remain constant for Reynolds numbers up to 



8 6 



10 (30-m-diameter prototype). Data for Reynolds numbers for 10 to 



g 

 10 are not available and cannot be obtained in the laboratory; thus, a 



test of the large scale anchor is the only true test of the validity of 

 this engineering judgment. After achieving a stable free-fall shape, 

 this model would require further evaluation to determine the effects of 

 realistic induced perturbations on stability. 



Then, evaluation of the behavior during seafloor approach is neres- 

 sary to determine the water pressure distribution on the underside of 

 the anchor, the velocities of the water escaping from beneath the land- 

 ing anchor, and the anchor deceleration due to the trapped water (or 

 water-cushion effect). An analytic approach followed by verifying moael 

 tests appears appropriate to obtain this deceleration information for 

 the case of a stably falling, horizontal anchor approaching a horizontal 

 seafloor. Following this simple case, the more normal case of a sloped 

 seafloor and a perturbed anchor must be addressed. Preliminary informa- 

 tion indicates that the water-cushion effect will work to orient the 

 anchor parallel to the seafloor while slowing its descent rate. Relia- 

 ble analysis techniques are needed here to predict the orientation of 

 the anchor during its descent and especially at the point of contact 

 with the seafloor. The exiting water velocity, water pressure distri- 

 bution, and the anchor velocity, orientation, and angular momentum data 

 are all required input to the following soil penetration/deceleration 

 analysis and in turn to the anchor structural design to resist possible 

 loadings during landing. 



14 



