Efficient Evaluation of Dynamic Response Data with a Linearized Frequency Domain Solver at Transonic Separated Flow Conditions

Abstract

Each perturbation of an aircraft state in trim induces aerodynamic loads on wings, con- trol surfaces and other parts of an aircraft. These loads have to be quantified for a wide range of flight states covering the flight envelope. Small disturbance approaches based on the Reynolds-averaged Navier Stokes equations fulfil the requirements of efficiently predict- ing accurate dynamic response data. These time-linearized methods have been successfully applied in flight dynamic and aeroelastic analyses for moderate flight conditions. Small disturbance approaches on the basis of Navier-Stokes solvers have become most often the right choice, for example in flight dynamic and aeroelastic analysis, to combine efficiency and accuracy for predicting dynamic response data. However, in complex flows exhibiting shock-induced separations, deficits in robustness of the iterative solution methods often lead to simplifications of the equations and thus reducing the quality of the computed results. The presented linearized frequency domain solver has shown accurate results compared to nonlinear time-accurate unsteady simulations for attached flow conditions. The area of application is extended to separated transonic flows demonstrating the method’s capability to accurately capture strong shock-boundary interactions. Deriving the exact linearization of the turbulence model as well as implementing a robust method to solve the stiff linear systems are key tasks to achieve this target. Results are presented for the LANN wing undergoing rigid body motions comparing dynamic derivatives of lift and moment coeffi- cients between the linearized frequency domain solver and its time-domain counterpart. In addition, local surface pressure and skin friction coefficients are analysed at two span sta- tions. The presented linearized frequency domain solver (TAU-LFD) has shown accurate results in comparison to fully time-accurate unsteady simulations at separated transonic flow conditions.