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Two-ray cylinder model (TRCM) for elongated scatterers

Source: R/model-trcm.R
TRCM.Rd

Computes the far-field scattering amplitude and related quantities for elongated fluid-like scatterers using the two-ray approximation model, as described by Stanton et al. (1993, 1998). The two-ray model is a high-frequency ray-based approximation that accounts for interference between reflections from the front and back interfaces of the scatterer, along with a directivity pattern that depends on the scatterer's orientation and curvature. The model is computationally efficient and captures the essential physics of acoustic scattering from elongated bodies such as zooplankton, particularly at high frequencies where the acoustic wavelength is much smaller than the organism size. The model supports both straight and bent cylinders, with the bent cylinder formulation incorporating the radius of curvature to account for body shape effects on the directivity pattern. For a fuller derivation and implementation discussion, see vignette("trcm-theory", package = "acousticTS").

Usage

This model is accessed via:


target_strength(
  ...,
  model = "TRCM",
  radius_curvature,
  radius_curvature_ratio,
  radius_cylinder_fun,
  sound_speed_sw,
  density_sw
)

Arguments

radius_curvature

Radius of curvature for bent cylinders (\(m\)). If NULL, the model assumes a straight cylinder unless radius_curvature_ratio is specified.

radius_curvature_ratio

Ratio of radius of curvature to body length (\(\rho_c / L\)). Used to compute radius_curvature if not explicitly provided. Default is NULL.

radius_cylinder_fun

Method for selecting the representative radius when the cylinder has variable radius. One of "center" (default), "mean", "median", or "max".

sound_speed_sw

Seawater sound speed (\(m~s^{-1}\)).

density_sw

Seawater density (\(kg~m^{-3}\)).

References

Stanton, T.K., Chu, D., Wiebe, P.H., and Clay, C.S. (1993a). Average echoes from randomly oriented random-length finite cylinders: Zooplankton models. The Journal of the Acoustical Society of America, 94: 3463-3472.

Stanton, T.K., Chu, D., Wiebe, P.H., Martin, L.V., and Eastwood, R.L. (1998). Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms. The Journal of the Acoustical Society of America, 103: 225-235.

Stanton, T.K., Chu, D., and Wiebe, P.H. (1998). Sound scattering by several zooplankton groups. II. Scattering models. The Journal of the Acoustical Society of America, 103: 236-253.

See also

target_strength, FLS, Cylinder, cylinder