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Cavity

⚠️ NOTE: These are advanced workflow examples showing direct solver access, stability analysis, and specialized workflows. They do NOT use the standard RL interface.

Looking for standard RL examples? See Getting Started for env.reset() / env.step() interface.

The open cavity is a classic CFD benchmark problem demonstrating recirculating flows and shear-layer instability.

Physical Description​

Configuration:

  • Open square cavity (1×1) with moving top wall
  • Inlet velocity: U = 1.0
  • All other walls: no-slip (U = 0)
  • Reynolds number Re = 7500

Quick Start​

1. Flow Simulation​

Run open cavity at Re=7500:

python run-transient.py

What it does: Simulates turbulent cavity flow from perturbed base state Outputs:

  • output/stats.dat - Time series of CFL, KE, TKE
  • Console shows evolution of kinetic energy and turbulent kinetic energy

Prerequisites: Requires steady state checkpoint from solve-steady.py

2. Find Steady State​

Solve for steady flow using Newton iteration with Reynolds ramping:

python solve-steady.py

What it does: Computes steady base flow for high-Re cavity Uses ramping: 500 → 1000 → 2000 → 4000 → 7500 for convergence Outputs:

  • output/7500_steady.h5 - Steady flow checkpoint for restart
  • output/7500_steady.pvd - Paraview visualization Prerequisites: None

3. Stability Analysis​

Compute eigenvalues of steady flow:

python stability.py --Re 7500 --num-eigs 10

What it does: Linear stability analysis using Arnoldi iteration Purpose: Identify unstable modes leading to shear-layer instability Outputs: Eigenvalues, eigenvectors, growth rates Prerequisites: Optional (can compute steady state internally)

4. Complete Workflow​

Two-stage simulation: steady solve + perturbed transient:

python unsteady.py

What it does: Demonstrates transition from steady to unstable flow Stage 1: Solve steady state with Reynolds ramping (500 → ... → 7500) Stage 2: Add perturbation and run long transient (Tf=500) Outputs: Time series, Paraview animations, TKE evolution Prerequisites: None (computes steady state internally)

MPI Parallelization: All scripts support parallel execution:

mpirun -np 4 python <script-name>.py