Cylinder Wake: Boundary Layer Separation & Drag Crisis

This wind-tunnel simulator visualises one of aerodynamics' cleanest textbook results: how a thin viscous boundary layer decides where flow separates from a bluff body, and how that single decision controls drag. A circular cylinder sits in a virtual test section; the free-stream airspeed and model diameter set the Reynolds number, and a trip toggle forces early transition the way dimples do on a golf ball. Live tracer particles follow the same potential-flow field used to derive the theory, peeling into a separated wake exactly at the angle the physics predicts — narrow and low-drag when the boundary layer is turbulent, wide and high-drag when it's laminar — while readouts track Reynolds number, drag coefficient, separation angle and Kármán vortex-shedding frequency in real time.