Let a pulse leave, or reflect it back

Current-run teaching example · actual FDTD snapshots · 2D TMz · single mesh

An absorbing boundary represents an open environment. A conducting wall sends waves back into the model. Start the movie and watch the same pulse in both: the open box becomes quiet while reflections keep crossing the closed box.

The lower plot is the electric field at the green probe. The vertical cursor marks the exact simulation time of the frame above. It follows stored field samples; playback does not run a simulation in your browser.

The colors show signed Ez / Eref, with one fixed linear scale for both models and all frames. Eref is the largest absolute recorded interior field outside a 4 mm radius around the current source. Source pixels can saturate; the raw values remain in the download. This is a 2D field cross-section, not a finite 3D antenna or cavity.

Download the complete generator. It uses Simulation, SnapshotSpec, and the physical coordinates and frame times in Result.snapshot_axes. It also generates the dielectric interface and cavity standing wave.

For the solver version used here:

git clone https://github.com/bk-squared/rfx.git
cd rfx
git checkout a9054338616b91bb1364699882c2530fa29a0048
python -m pip install -e .
curl -fLO https://remilab.ai/rfx/gallery/assets/current-visuals/field_movies.py
# Install ffmpeg using your operating system's package manager.
JAX_PLATFORMS=cpu PYTHONPATH=. python field_movies.py \
  --case boundary-reflection --output field-movies

The local output contains the full field arrays, probe CSV, poster, MP4 and manifest. --render-only redraws these saved arrays without solving again. The script prints preflight findings before each run and refuses preflight errors. These two vacuum models returned no preflight findings.

• Probe CSV, in seconds and V/m
• Selected field arrays and all probe samples, NPZ
• Model, normalization, preflight and checksums, JSON

The small NPZ contains every 16th movie frame at full spatial resolution, with its actual coordinate arrays, step numbers and time stamps. Re-running the generator retains every movie frame locally. Load with numpy.load(path, allow_pickle=False); fields end in _ez_V_per_m, coordinates in _x_m/_y_m, and times in _frame_times_s.

Try moving the source or changing the domain size, then rerun. Compare when the first reflected wave reaches the same probe. CPML is a finite numerical absorber and can produce residual reflections; this example does not measure its reflection coefficient or an absorption percentage.

Generated on the CPU with RFX solver source a9054338. The manifest records the full source commit, generator hash and environment. The checks confirm finite fields, recorded frame steps and realized display coordinates. No mesh refinement or accuracy convergence was performed, and no S-parameter, decay rate, or performance claim follows from the movie.

Continue with boundary choices or the API reference.