Wind tunnel measurements of a cuboid external load model

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Bier, N.
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The prediction of the aerodynamic behavior of cuboid cargos in the vicinity of a releasing transport aircraft or as a slung load under a transporting helicopter is a challenging task, but can help to reduce the number of costly and time-consuming flight tests and wind tunnel campaigns. Against this background the DLR F20 model was built as a generic load configuration. It resembles a 108'' x 88'' cargo pallet in a scale of 1:2 and is equipped with 155 static and 5 unsteady pressure taps. Extensive measurements in the DNW-NWB low speed wind tunnel in Braunschweig were conducted as a first step to build a database for the aerodynamic coefficients of such cargo configurations and as a means to validate numerical simulations. Mean integral forces and moments were measured and a subsequent analysis of the data in the frequency domain showed no aerodynamically introduced frequencies. Surface pressure measurements were investigated and the traces of conical vortex structures were visible. Numerical in-tunnel simulations in the form of a feasibility study showed a good agreement with experimental values for configurations with small front surface and can serve as a means to apply suitable wind tunnel corrections.