Reik Thormann

Linear-Frequency-Domain Predictions of Dynamic-Response Data for Viscous Transonic Flows

Determining the flutter boundaries for full aircraft configurations by time-accurately solving the Reynolds-averaged Navier–Stokes equations is prohibitive with respect to computational expense, as the unsteady aerodynamic loading must be predicted for a wide range of flight conditions, frequencies, and structural mode shapes. Nonetheless, there is an increasing demand to accurately predict flutter boundaries in the viscous transonic regime—a demand, which, until recently, could only be satisfied by high-fidelity Reynolds-averaged Navier–Stokes methods. Brought to application readiness over the last years, time-linearized/small-disturbance methods, however, have been shown to satisfy this demand as well. They retain the Reynolds-averaged Navier–Stokes method’s fidelity to a high degree, at a substantially reduced computational expense. Such a method is presented here on the basis of the TAU–Reynolds-averaged Navier–Stokes method. Denoted as the TAU linear-frequency-domain method, it is validated for both ...

Efficient Evaluation of Dynamic Response Data with aLinearized Frequency Domain Solver at TransonicSeparated Flow Conditions

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