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Pinball

⚠️ NOTE: These are advanced workflow examples showing direct solver access 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.

Flow around three cylinders in triangular arrangement - a challenging benchmark for flow control.

Physical Description​

Configuration:

  • Three cylinders in equilateral triangle arrangement
  • Cylinder radius: 0.5
  • Uniform inflow from left (U∞ = 1.0)
  • Reynolds number Re = 30-150

Key Phenomena:

  • Re = 30: Steady symmetric flow
  • Re = 150: Complex unsteady wake with three-body interactions
  • Wake can exhibit mode switching between symmetric/asymmetric states
  • Chaotic dynamics possible at higher Re

Quick Start​

1. Basic Simulation​

Run unsteady pinball flow at Re=30:

python run-transient.py

What it does: Simulates flow around three cylinders showing wake interactions Outputs:

  • coeffs.dat - Time series of CL for all three cylinders
  • Console shows forces on each cylinder Prerequisites: None

2. Find Steady State​

Solve for steady flow at Re=80 using Newton iteration:

python solve-steady.py

What it does: Computes steady state (or unstable equilibrium) for stability analysis Uses ramping: 40 → 60 → 80 for better convergence Outputs:

  • output/pinball_Re80_steady.h5 - Checkpoint for restart
  • Paraview files for visualization
  • Force coefficients for all three cylinders Prerequisites: None

3. Observe Wake Dynamics​

Two-stage simulation: steady solve + perturbed transient:

python unsteady.py

What it does: Demonstrates transition from steady state to complex wake dynamics Stage 1: Solve steady state with Reynolds ramping (40 → 60 → 80 → 100) Stage 2: Add perturbation and run transient (Tf=200) Outputs: Time series, Paraview animations, force data for all cylinders Prerequisites: None (computes steady state internally)

MPI Parallelization: All scripts support parallel execution:

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