Vertical Farm CO2 Depletion 2D: Diffusion-Advection Column

This is a 2D companion to the 3D vertical-farm CO2 simulator, built around a genuinely different, finer-grained piece of physics. Instead of chaining four well-mixed tier compartments together, it numerically integrates the continuous 1D advection-diffusion-reaction PDE for CO₂ concentration along the height of the rack's air column: fresh, CO₂-enriched supply air enters at the bottom as a fixed boundary condition, is carried upward by advection and turbulent diffusion, and is drawn down everywhere a leaf canopy sits by a Michaelis-Menten uptake term. A finite-difference solver re-computes this field frame by frame, so the color gradient and the profile curve beside it are the literal output of the integration — and the panel shows a live mass-balance residual proving the discrete scheme conserves CO2 exactly the way the continuous equation says it should: inflow at the bottom minus outflow at the top minus everything the canopy removed.