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4.9 Numerical model summaries

This section summarizes available underwater acoustic propagation models. These models are applicable to work in sonar technology (e.g. sonar design and operation) and in acoustical oceanography (e.g. oceanographic research and data analysis). As is true of any summary of this nature, the information represents a snapshot in time of the present state-of-the-art. While comprehensive in coverage, this summary does not claim to be exhaustive.

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Range (km)

Figure 4.14 RAYMODE arrival structure diagram. This graph displays receiver angle versus horizontal range for selected rays representing bottom bounce (BB) and CZ paths. The CZ paths are associated with the near-axis features at 45, 90 and 135 km (Yarger, 1982).

0 50 100 150

Range (km)

Figure 4.14 RAYMODE arrival structure diagram. This graph displays receiver angle versus horizontal range for selected rays representing bottom bounce (BB) and CZ paths. The CZ paths are associated with the near-axis features at 45, 90 and 135 km (Yarger, 1982).

In order to optimize the utility of this information, the models are arranged in categories reflecting the basic modeling technique employed (i.e. the five canonical approaches) as well as the ability of the model to handle environmental range dependence. Such factors define what is termed "domains of applicability." Hybrid models occasionally compromise strict categorization, and some arbitrariness has been allowed in the classification process. The environmental range dependence considers variations in sound speed or bathymetry. Other parameters may be considered to be range-dependent by some of the models, although they are not explicitly treated in this summary.

The specific utility of these categories is further explained below. In sonar design and operation problems, for example, the analyst is normally faced with a decision matrix involving water depth (deep versus shallow), frequency (high versus low) and range-dependence (range-independent versus range-dependent ocean environments). Jensen (1982, 1984) developed a very useful classification scheme for optimizing this decision logic against the available modeling approaches and their domains of applicability. Jensen's scheme is slightly modified here to accommodate the five modeling approaches utilized in this book (Figure 4.18). The following assumptions and conditions were imposed in the construction

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