Velaiele Dynamics Assooiated with Submarine Rescue 



CO 



_J 



z 



I— 

 U 



2 



300 



400 



FREQUENCY (CPS7 



Fig. 22. Pitching Moment Power Spectral Density vs. Frequency 

 (Model Sccde Values Shown) 



was obtained from the integrated power density spectrum. Then 

 using Strouhal number and Reynolds number scaling, the full-scale 

 unsteady (a.c.) comiponent standard deviation of forces and moinents 

 were computed. For the corresponding test conditions, the inter- 

 action data were used to compute the fiall- scale magnitude of the 

 steady components. In the simulation the unsteady forces were 

 approximated by a white noise perturbation on the current used to 

 generate the steady forces. Based on the standard deviation of the 

 test data a ratio of unsteady (a. c. ) to steady (d. c. ) forces of 0,15 

 was selected in the frequency range from to 0,082 Vq Hertz. 



The ducted thrusters of the DSRV are presently designed to 

 provide 830 lbs of normal and lateral force and are required to 

 maintain vehicle heading in a 1 knot current. The worst side force 

 condition, obtained during tests with the sail rolled 22.5 degrees 



1163 



