What is wind tunnel testing and why is it important?

Wind tunnel testing involves placing scaled or full-size models in a controlled airflow to measure aerodynamic forces, pressures, and flow visualization. It is important for validating CFD predictions, studying complex flow phenomena, measuring stability derivatives, and certifying aircraft designs. Key considerations include Reynolds number matching, model fidelity, wall interference corrections, and instrumentation accuracy. Wind tunnels range from low-speed subsonic to hypersonic facilities depending on the application.