A square cross-section of the cube is held on a load-cell arm inside an airflow. Drag force is computed live from the real drag equation F = ½·ρ·v²·Cd·A, with the drag coefficient and projected frontal area both depending on the cube's angle of attack, exactly as a wind-tunnel balance would measure it. The wake sheds alternating vortices behind the body (vortex shedding), the real reason bluff bodies like this buffet and hum in real airflow.