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FCMS

Source: vignettes/fcms/index.Rmd
index.Rmd

Overview

Benchmarked Validated
Theory Implementation

These pages follow the finite-cylinder modal-series literature for straight circular cylinders near broadside (Stanton 1988, 1989).

The finite cylinder modal series solution (FCMS) is the package’s geometry-matched cylinder family for straight circular cylinders. It keeps the exact cylindrical-harmonic treatment of the cross-section and closes the finite-length problem with the standard near-broadside coherence factor.

Core idea

Solve the circular cross-section exactly in cylindrical partial waves, then multiply by the finite-length directivity factor that accounts for the coherent addition along the cylinder axis.

Best for

  • Straight finite cylinders near broadside
  • Rigid, pressure-release, liquid-filled, and gas-filled cylinder comparisons
  • Reference checks for cylinder-like targets before using higher-level approximations

Supports

  • Cylinder shapes on FLS or GAS objects
  • Near-broadside monostatic target strength
  • Fluid and gas interiors parameterized relative to seawater as medium 1

Main assumptions

  • Circular cross-section and straight centerline
  • Broadside or near-broadside incidence
  • Homogeneous interior material properties for penetrable cases
  • No elastic shear support in the interior

Validation status

  • Benchmarked against the canonical finite-cylinder spectra stored in benchmark_ts.
  • Validated against the echoSMs finite-cylinder implementation.

Family pages

  • Implementation: spectra, result extraction, and comparison tables
  • Theory: cylindrical modal reduction, boundary conditions, and finite-length factorization

References

Stanton, T. K. 1988. “Sound Scattering by Cylinders of Finite Length. I. Fluid Cylinders.” The Journal of the Acoustical Society of America 83 (1): 55–63. https://doi.org/10.1121/1.396184.
———. 1989. “Sound Scattering by Cylinders of Finite Length. III. Deformed Cylinders.” The Journal of the Acoustical Society of America 86 (2): 691–705. https://doi.org/10.1121/1.398193.