Computational Determination of Dynamic Stability Derivatives

ABSTRACT Dynamic stability derivatives are essential for flight dynamics analysis, simulation, and control design, but their experimental determination is often costly and technically demanding. This paper investigates three CFD-based approaches for determining dynamic stability derivatives in compressible, viscous flow: (i) steady-flow simulations in a non-inertial (moving) reference frame for rotational derivatives, (ii) the Forced Oscillation Method (FOM) with prescribed harmonic motion, and (iii) the Indicial Response Method (IRM) based on step-response histories in angle of attack or pitch rate. All methods are implemented in ANSYS Fluent using the Moving Reference Frame and Dynamic Mesh capabilities and are applied to the Basic Finner missile (high-speed, low- α regime) and the SZD-9 Bocian glider (low-speed, 0° ≤ α ≤ 20°). For the Finner model, the computed pitch-damping sum ( c m α + c m q ) agrees with experimental data within the observed scatter, with both FOM and IRM showing consistent behavior except at M = 1.2, where a discontinuity is present in both simulations and measurements. For the glider, roll-damping derivatives C l p from the Moving Reference Frame and FOM approaches agree in attached flow, diverge in partially separated conditions, and reconverge in fully separated flow. The results identify flow regimes where each method can be used with higher confidence and highlight conditions requiring increased caution and additional validation.