Active Acoustics using Bellhop-DRDC: Run Time Tests and Suggested Configurations for a Tracking Exercise in Shallow Scotian Waters

摘要

This research is designed to provide support for active sonar projects resulting from the bilateral agreement that has recently been signed with the US Navy to jointly investigate tactical oceanography technologies. In the context of the tracking exercise requirements, the model Bellhop-DRDC has been enhanced to produce active transmission loss and reverberation. Critical to the implementation of this model in the tracking exercise is the runtime. This report documents the parameters that affect runtime in Bellhop and recommends a configuration designed to provide the best result for the tracking exercise in terms of the accuracy/runtime trade-off. A Scotian shelf area was chosen as a representative exercise environment. Based on the timing and accuracy tests described in this report, it is recommended that for operation at 1000 Hz or higher in 260m water depth or less, the angle fan can be set to 30 ( 15 ) and a kill-after-bounce number of 7 can be safely employed to show less than 2dB error over all range and depth points in a 20km box. Using this configuration in Bellhop, a simulated test sequence was constructed to compute arrays of transmission loss and reverberation for 18 assets (one source, one towed array and 16 buoys) as a function of bearing angle, range (1/2km spacing out to 20km) and depth (51 points in 260m depth). This sequence was exercised for various numbers of lines of bearing and SSP points. These tests showed that the runtime needed for an initial calculation for all 18 assets ranged up to 12 minutes for 15 lines of bearing. The ping-by-ping update runtimes ranged up to 80 seconds for 15 lines of bearings and the 2 moving assets (one source and one towed array). These times were recorded using a 1.5GHz Pentium 4 processor.