Countercurrent Heat Exchange in Animal Limbs: 2D Cross-Section

Many cold-adapted and aquatic animals keep their core warm without wasting energy heating an entire limb: arteries and veins run in tight parallel bundles so outgoing warm blood pre-heats the cooled blood returning from the extremity, and vice versa. This simulator solves the same discretized 1D countercurrent heat-exchanger model as the full 3D version — advection along the artery and vein plus a direct thermal coupling between them and heat loss to the environment at the extremity — but renders it as a draggable 2D limb schematic paired with a live temperature-profile graph along the limb's length. Adjust ambient temperature, core body temperature, blood flow rate and coupling strength, or flip the vein to co-current flow, and watch the extremity temperature and the fraction of core heat retained respond live.