Pressure Mapping on Buildings
When wind strikes a building, it creates a complex pressure distribution across every surface. The windward face experiences positive pressure as moving air decelerates against the wall — this is the push you feel when facing into a strong wind. Every other surface experiences suction: the flow separates at sharp edges, accelerates around corners, and creates low-pressure zones that pull outward on walls and roofs. The pressure coefficient Cp nondimensionalizes this distribution, making it independent of wind speed and applicable at any scale.
The Importance of Wind Angle
Building codes typically require checking multiple wind directions because the worst loading case varies by surface. Normal wind (0°) creates the highest windward pressure but moderate side suction. At 30-45° oblique incidence, corner vortices generate the most extreme local suctions — Cp values of −2 to −3 that govern cladding and roofing design. This simulation lets you rotate the wind angle and watch the pressure distribution transform, revealing why wind tunnel studies test every 10-15° of wind direction.
Understanding the Visualization
The building cross-section is shown with color-coded pressure coefficients on each face. Red indicates positive pressure (pushing inward), blue indicates suction (pulling outward), with intensity proportional to |Cp|. Wind streamlines show how flow separates at edges and forms recirculation zones behind the building. The dynamic pressure q = 0.5ρV² converts Cp into actual pressures in Pascals — at hurricane wind speeds (60 m/s), even moderate Cp values produce enormous forces.
Engineering Design Applications
Structural engineers use Cp distributions to calculate frame loads and foundation reactions. Facade engineers use them to design cladding connections that resist peak suctions without over-designing typical areas. HVAC engineers use them to position air intakes in positive-pressure zones and exhaust vents in suction zones. The net pressure across the building envelope also drives air infiltration, affecting energy efficiency and indoor air quality. Every tall building and most complex low-rise structures undergo wind tunnel testing to determine accurate Cp distributions.