Experiments with an adaptable-wall wind tunnel for large lift

Experiments have been carried out in a demonstration wind tunnel of the adaptable-wall type designed for the testing of high-lift configurations, such as powered-lift V/STOL aircraft. The simulated flight vector makes a large angle (30-40 deg) relative to the tunnel axis, so that the model's wake lies in a benign position. Simulation of flight at the desired speed and angle is accomplished by iteratively matching conditions at an interface within the tunnel to the calculated, updated outer flowfield. Measurements were made with a traversing laser-Doppler-anemometer system. The test model in these experiments was a V/STOL transport aircraft model with lower-surface blown wing flaps. Under test conditions, the powered wing-wake made a large angle with the flight direction, and wake positions were measured and are shown. Results show that the iterative procedure successfully reduced matching discrepancies at the interface. Typically, the best match was reached after about six or eight iterations, and this match represents precise simulation at the model to within 1% of stream speed.