Wind-turbine model rotors require a well-defined incoming airflow if aerodynamic measurements are to be meaningful. A free-jet wind tunnel produces this test flow by discharging a controlled air jet into a larger room or test hall.
FlowMotion used CFD to support the design of a free-jet wind tunnel for model rotors. The calculations included not only the jet itself but also the return flow through the surrounding hall.
The quality of the test flow depends on the velocity distribution and turbulence level in the jet at the rotor position. At the same time, the discharged air must return to the fan or inlet without creating strong recirculation that disturbs the measurement region.
The simulations showed the complete airflow pattern in the facility and made it possible to evaluate nozzle geometry, test-section dimensions and the available return-flow paths.
By considering the free jet and hall return flow as one coupled aerodynamic system, the wind-tunnel layout could be optimised before construction.
