Influence of Excitation Frequency on Airship Dynamic Stability Coefficient Calculations

Interest in airships has been growing in recent years because of their ability to serve both as stratospheric platforms (High Altitude Pseudo Satellite) and as an alternative for heavy air transportation. Due to this interest, efforts have been made to properly define the dynamic and kinematic models of such vehicles, which requires an adequate knowledge of the dynamic stability derivatives. However, we have noticed that the effect of the selected excitation frequency has been widely underestimated in the literature. Within this work, we prove that the contribution of this effect is highly relevant for the calculation of the dynamic stability derivatives and should not be neglected. By numerically simulating an ellipsoid body under different lateral or pitch forced motions, we found that the resulting stability derivatives can vary by up to 20%. We also found that the selected turbulence model significantly influences the results, especially the lateral stability derivative. These observations emphasize the importance of turbulent and viscous effects in the calculation of dynamic stability derivatives. They also highlight the need to carefully consider both the selected frequency and turbulence model when defining the airship’s dynamic models.