Chuban A.V., Chuban V.D.
DOI Number: N/A
Conference number: IFASD-2015-204
There has been considered the task of non-linear transonic aerodynamics module to be integrated in the program that allows to analyze frequency-domain flutter performance for different aircraft configurations. New aerodynamics block is based on rapid numerical integration of the Euler unsteady equation linearized on the steady solution. The algorithm used is based on the iterative coupling of non-viscous solution for external flow and solution for spatial compressible viscous boundary layer. Aerodynamic block performs calculation of unsteady aerodynamic flows for aircraft rigid motions and elastic vibration modes at several values of Strouchal numbers Sh = ωb/V, ω — angular frequency, b — mean aerodynamic chord, V — true airspeed. The elastic beam model makes use of simplified panel aerodynamic configuration whereas aerodynamic block utilizes 3-D aircraft model. Interaction between flutter calculation program and aerodynamic block is carried out using interpolation of elastic beam model displacements and velocities on to the 3-D aerodynamic model grid nodes and inverse interpolation of aerodynamic forces on to the elastic beam model grid nodes. Values of the aerodynamic coefficients calculated for several Strouchal numbers are used as reference points for the development of the third order fractional interpolation for each aerodynamic coefficient. Use of aerodynamic coefficient frequency approximations allows to solve flutter equations in frequency domain as well as to determine dynamic system poles. Standard methods of poles trajectory plotting with zero-damping points tracing is applied to determine critical flutter parameters. Using mathematical model of the next generation airliner as an example the comparison is made as to the new CFD block with well-known DLM method for aerodynamic coefficients, pressure distribution and flutter analysis results. The comparison illustrates that both methods gave almost identical results for subsonic flow, but for transonic flow the difference between methods is remarkable.