As part of the PLASTICBEACH project (EC2CO), an advanced modeling framework combining the SWASH wave model and the TrackMPD Lagrangian transport model was employed. The framework was used to simulate laboratory experiments of microplastic transport dynamics conducted by Forsberg et al. (2020) in the CASH wind-wave flume (SeaTech–MIO), specifically under one of the two windless hydrodynamic scenarios. The aim was to validate the model's ability to reproduce the transport of diverse microplastics (varying in density, shape, and size) in wave-dominated environments over a beach profile.

The model domain replicated the flume’s 6 m length, with a still-water depth of 0.22 m and a 1:20 linear slope starting at x = 1 m. The computational grid comprised 175 horizontal points (3.45 cm resolution) and 15 vertical layers. Simulations were executed with a 0.05 s time step for both hydrodynamic and particle-tracking calculations. The SWASH model was forced at the left boundary (wave maker) with regular waves of 1.2 s period, employing a Sommerfeld condition at the right boundary (beach). To ensure consistency with the experimental setup, the wave height at the boundary was adjusted to match the measured value (H = 9.2 cm) at the first gauge (x = 1.8 m) in the experiment.

In line with the flume experiments, TrackMPD incorporated six types of microplastics: nearly spherical pellets, fibers, and sheets, both denser and less dense than coastal waters. The particle release in the model mirrored the experimental configuration, with 50 particles of each type, totaling 300, introduced at the start of the shoaling zone. Each simulation lasted 10 minutes, allowing the system to reach a stationary state. Multiple runs of each scenario were conducted to ensure consistency and reproducibility of the results.