A gas bubble released in a liquid accelerates until drag balances buoyancy. In the creeping (Stokes) regime, v = (2/9)Δρ g R²/μ, Re < 1 and the bubble stays spherical. At intermediate size inertia and surface tension compete (Eötvös number Eo = Δρ g d²/σ), giving oblate wobbling bubbles; for large Eo the bubble becomes a spherical cap rising at v ≈ 0.711√(gR) (Davies-Taylor).

The streamlines are the Stokes flow past a rigid sphere, matching the drag law of the 3D lab; a clean gas bubble would slip and rise faster (Hadamard-Rybczynski). The approach to terminal speed uses added mass plus Stokes drag: τ = 2R²(ρg+ρ/2)/(9μ). Regime thresholds are engineering simplifications, not a full Grace-diagram model. "Time scale" speeds up the clock only.

The check button integrates the force balance with an independent explicit time-stepper and compares it with the closed form.