Numerical simulation of unsteady flows around helicopters was conducted to investigate the aerodynamic interference between main rotor and other components. The effect of rotor downwash on the behavior of air-launched free-flight rockets and their plume was also investigated. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between main rotor, tail rotor, fuselage, and launched rockets. The flow solver was also coupled with six degree-of-freedom equations of motion to predict the trajectory of free-flight rockets air-launched from a helicopter. For the validation of the flow solver, calculations were made for the rotor-fuselage aerodynamic interaction of the ROBIN (ROtor Body INteraction) configuration and for a complete UH-60 helicopter configuration consisted of main rotor, fuselage, and tail rotor. Comparison of the computational results was made with available experimental data. It was found that significant mutual interference exists between main rotor and other components as confirmed by the unsteady flow characteristics and the aerodynamic loads. Simulation of air-launched rockets from an UH-60 helicopter showed that rotor downwash has non-negligible effect on the trajectory of the rocket and its plume development, which may potentially affect the safety and the reliability of other equipments.
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