Subs Model A2 in High Currents (> 2.5 knots)

Nortek 500 kHz ADP mounted in Subs

                                                

SUBS A2 Tow Test Results

 

Equipment:

SUB, Model A2

Nortek ADP

Nortek Battery Pack

Custom attitude and compass package (BIO) with direct readout and data logger

 

Tow Tank trials were undertaken in November 1999, using a Model A2 SUB, with Nortek ADP and external battery pack mounted.  G. Fowler, P. Eng., of Bedford Institute of Oceanography on our behalf, conducted trials at a Canadian Government tow tank in Ontario, Canada. Instrumentation was assembled and installed by J. Hamilton, Physical Scientist at BIO, who supervised trials.  Hamilton also plotted the data presented herein.  

 

The purpose was to test three-axis stability at various current speeds.  Previous trials had indicated that with the standard battery case suspended horizontally below the SUB, the pitch angle exceeded ADP manufacturer’s design criteria at moderate speeds.  A high performance tail assembly had been designed for these trials, which was expected to improve pitch self-correction.

 

Trials were undertaken with a battery pack slung horizontally below the SUB.  The tow tank carriage did multiple runs of increasing speeds, commencing at .25 m/s, followed by .5m/s, 1.0 m/s and with the final run at 2 m/s (4 knots).  

 

Pitch remained stable at all speeds, not exceeding 80 at any speed.  

Roll remained stable and minimal over the full range. 

Heading misalignment had corrected below .25 m/s.

 

Data was plotted for each speed.  Plots are attached.

 

Conclusion:

 

In this configuration, a Nortek ADP mounted in a SUB is a stable package, with all results well within manufacturers specifications and user requirements for applications with current speeds of not more than 4 knots. Data trends might indicate that higher speeds could be accommodated. The high performance tail is required to compensate for increased drag of the external battery pack and the large lobes of the 500 kHz ADP.  This tail configuration must be the standard on all Nortek units.


Data Plots – Nortek ADP Tow Tank Trials

 

 

 

Note 1:   Plus pitch is nose down.