12: Submerged Bar Benchmark (Beji & Battjes)

[philipnickel]

Description

Simulate the classic Beji & Battjes (1994) submerged bar experiment and compare with laboratory data. This is the primary experimental validation case.

Background

Waves propagate over a trapezoidal bar, undergo nonlinear shoaling, and release bound harmonics as free waves. This tests:

• Variable bathymetry handling
• Nonlinear wave-wave interactions
• Accurate dispersion (free harmonics travel at different speeds)

Tasks

• Define bar geometry (Case A from original experiment)
  • Offshore depth: h₀ = 0.4 m
  • Bar top depth: h_bar ≈ 0.1 m
  • Up-slope: 1:20
  • Down-slope: 1:10
• Set up numerical wave tank
  • Generation zone at inlet
  • Absorption zone at outlet
  • Sufficient length for full bar + propagation
• Configure input wave
  • H = 0.02 m
  • T = 2.02 s
  • Stream function solution at depth h₀
• Implement gauge output at experimental locations
  • x = 4, 10.5, 13.5, 14.5, 15.7, 17.3, 19.0, 21.0 m
• Run simulation for 40+ seconds
• Compare with experimental data

Acceptance Criteria

• Simulation runs stably for full duration
• Harmonic generation visible in time series over bar
• Free harmonic dispersion visible after bar
• Time series qualitatively match experimental data
• Peak amplitudes within 20% of experimental values
• Phase agreement within 10%

Deliverables

• Time series plots at each gauge location
• Overlay with experimental data
• Spatial snapshot of wave field over bar
• Animation of full simulation

References

• Beji, S. and Battjes, J.A. (1994) "Numerical simulation of nonlinear wave propagation over a bar"
• Luth et al. (1994) experimental data