MODELLING OF DYNAMIC STABILITY DERIVATIVES USING CFD

摘要

An exploratory investigation into the use of a commercial Navier-Stokes time accurate code, Fluent, for simulating and predicting the combined pitch damping derivatives, C_(m_q) + C_(m_α), was conducted. The stable store, a low l/d finned missile like configuration, was used for the investigation. The derivatives were extracted from the response of the store, which was simulated by providing a initial disturbance and allowing the store to oscillate freely at the system natural frequency. The same setup, as used for the numerical simulations, was used for the experimental simulations. Static steady state runs were initially performed, and compared favourably to experimental results providing confidence in the mesh and solver parameters. The results of the numerical simulations did not compare favourably with the experimental results. The numerical investigations (both inviscid and viscous) overpredicted the derivatives compared to the experimental results by a factor of three. The time taken for the simulations was considered reasonable. The two main factors that need to be investigated, which may be causing the poor correlation, are the time step size and the experimental apparatus sting effects.