Evaluating the longitudinal stability of an UAV using a CFD-6DOF model

Dynamic meshes are meshes that change their shape and/or size to suit the domain changes over time. The aim of this work is the validation of a computational model of dynamic meshes in CFD for the prediction of the longitudinal dynamic of an UAV. Herefor it was necessary to use the 6DOF module of the commercial software ANSYS Fluent. The idea is to verify the tool functionality to make use of it in the generation of knowledge and information to feed a flight simulator. The validation was executed through the comparison of the simulation results and experimental data collected during an UAV test flight. To evaluate the airplane longitudinal stability an impulsive perturbation was introduced to its elevator when the airplane was in equilibrium (straight and level flight) and then the dynamic response was quantified. In the computational model the prevailing conditions during the flight were replicated. The obtained results for the altitude changes of the airplane, the pitch angle and longitudinal speed show a good correlation with the experimental data. The relative errors in magnitude, frequency and damping are lower than 21%, 7% and 11%, respectively, for the long period oscillation or phugoid. With these results the model was validated and the tool functionality was proved.