Computational and Experimental Static Stability Analysis of Rectangular Prisms

Rectangular prism-shaped cargo containers are being investigated for future aerial delivery and helicopter sling load operations. The aerodynamic stability characteristics of two representative container shapes, the 6-m (20-ft)-equivalent unit (TEU) and the internal slingable unit (ISU)-90, are analyzed using a combination of computational simulations and wind tunnel experiments. The study examines integrated forces and moments, as well as static stability, for the two shapes at Mach numbers of 0.15 and 0.2. Six models are used in total, three for each of the two container shapes, with axial, normal, and side orientations. The findings provide insights into the aerodynamic stability of rectangular prisms as cargo containers under various flight conditions, which have implications for aerial delivery and helicopter sling load operations. The scope of the data associated with these studies does not allow for a complete examination within this article, but the paper provides a general overview and selected examples of the available static and dynamic data, including observed trends. Specifically, the computational simulations and experimental surface flow measurements identify flow separation and reattachment processes that directly influence longitudinal, lateral, and directional stability.