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Damping, Recorders, and Outputs

Running a simulation is only useful if you can model physical energy dissipation (Damping), instrument the model to record responses (Recorders), and write files for visualization (Outputs).

Mental Model

  • Damping: Dissipation mechanisms (such as mass- and stiffness-proportional Rayleigh damping) applied to structural or soil elements to represent energy loss during dynamic simulations.
  • Recorders: Virtual sensors placed at nodes or elements. Instead of saving data for the entire model, you specify what to record (e.g. displacement, velocity, acceleration) and where to record it.
  • Outputs: The final artifacts produced by Femora, including solver input files (TCL), post-processing databases, and 3D visualization grids (VTK, JSON).

Think of recorders as cameras placed around a crash-test site. You do not need a camera on every single part of the vehicle; you place them at key interest points to capture data efficiently.

Where It Fits

Damping, recorders, and outputs are configured after assembly. Damping properties are assigned to regions, recorders are added as process steps, and outputs are written at the end:

Run Assembly
   ├─ Apply Damping to physical regions (e.g. model.damping.rayleigh)
   ├─ Define Recorders on node/element groups
   ├─ Add Recorders to Process steps (model.process.add_step)
   └─ Export Outputs (export_to_tcl, export_to_vtk)

Minimal Example

Applying Rayleigh damping, creating a node recorder for a group, and exporting the model:

from femora.core.model import Model

model = Model()

# (Configure and compile assembly here...)

# 1. Apply Rayleigh damping to a physical region
model.damping.rayleigh(
    name="soil_viscous_damping",
    alpha=0.20,
    beta=0.003,
    region=model.region.get("soil_domain")
)

# 2. Record displacements for ground surface nodes
surf_disp_rec = model.recorder.node(
    name="surf_disp_rec",
    response="disp",
    dof=[1, 2, 3],
    group=model.group.get("ground_surface")
)

# 3. Add the recorder to the process steps
model.process.add_step(surf_disp_rec, description="Record surface motion")

# 4. Export the assembled model to VTK for PyVista/ParaView
model.export_to_vtk("mesh_geometry.vtk")

For recorder and damping configurations, refer to the Recorder Manager API Reference and Damping Manager API Reference.

What Femora Stores

For damping, recorders, and outputs, Femora tracks: - Damping: Viscous coefficients, target element lists, and associated frequency-damping bounds. - Recorders: Target node/element groups, output file names, time step frequencies (dt), and requested response fields. - Outputs: Path references and output file writers.

Common Mistakes

Recording Too Many Nodes in 3D Models

In large-scale 3D models with hundreds of thousands of nodes, creating a recorder for all nodes will create massive files on disk, causing severe I/O bottlenecks and drastically slowing down solver execution. Always restrict recorders to targeted, named node or element Groups.