Ocean Bottom Smoothing in Bellhop – Linear and Curvilinear Interpolation

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Authors
  1. McCammon, D.F.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN);McCammon Acoustical Consulting, Waterville NS (CAN)
Abstract
The primary purpose of this task is to study the Curvilinear option for bathymetry interpolation and document its behaviour in Bellhop. The underlying goal is to determine if bottom smoothing will alleviate the discrepancy discovered between Bellhop and a Parabolic Equation model whereby a sharp discontinuity in bathymetry caused the predictions of the models to diverge. The results of the study show that the Curvilinear option is superior to the standard linear option over continuously curved surfaces such as elliptic and parabolic bottom profiles. Simple discontinuous profiles such as a peak, valley, shelf, or sawtooth also show improvement if the Curvilinear interpolation is restricted to a region close to the discontinuity. In this usage, the Curvilinear interpolation is mimicking the major features of the diffracted wave field about a point. Thus, the tentative conclusion is that the discrepancy previously discovered was caused by the neglect of the diffraction contribution in Bellhop. In tests using a complex measured profile from the Q290 field test, it was found that the Curvilinear option could produce transmission losses that were quite close in level and phase to those from PECan in the first 4 km of the track where the bottom was flat but rough. However, in the second part of the track where there were distinct seamounts, the comparisons degraded. In the course of this investigation, a bug was identified in Bellhop that appeared occasionally when using the Curvili

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Report Number
DRDC-ATLANTIC-CR-2009-099 — Contractor Report
Date of publication
01 Jul 2009
Number of Pages
68
DSTKIM No
CA033416
CANDIS No
532721
Format(s):
Electronic Document(PDF)

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