Sohveibev J Bentkowsky and Kerr 



Plots of typical power- spectral energy versus frequency in 

 model scale are shown in Figs. 21 and 22 for the unsteady normal 

 force and pitching moments acting on the DSRV. These conditions 

 were for the DSRV mated (Z^, = 0) athwartships on the forward hatch 

 of a downed submarine with no roll. 



The full-scale natural pitch period of the DSRV can range 

 from 41. 5 to 72 seconds , corresponding to a BG value of 1 to 3 

 inches and a weight of 7 5,000 lbs. This information shown in terms 

 of model data for a 1 knot current in Fig. 22 indicates that there is 

 no significant concentration of energy near the DSRV natural fre- 

 quency; therefore, motion excitation at resonant conditions will not 

 be significant. 



The standard deviation of forces and moments in model scale 

 were determined as the square root of the spectral energy, which 



Q. 



u 



Z 



UJ 



u 



LU 



o 



■ r- DSRV 

 ^P jh J — SUBMARINE 



T 



GROUND PLANE 



PSUB - ^* 

 ^SUB = 0« 



/Ha^ 



200 



FREQUENCY (CPS) 



300 



400 



Fig. 21. Normal Force Power Spectral Density vs. Frequency 

 (Model Scale Values Shown) 



1162 



