Comparison of Euler and Full Potential Methods for Unsteady Transonic Flow Calculations.

Kurzfassung

This paper presents the results of unsteady transonic flow calculation methods developed at the DLR Institute of Aeroelasticity for oscillating airfoils and wings. 2D Euler and Full Potential calculations in the nonlinear regime with pronounced shock dynamics at the conventional NACA0012 and the supercritical NLR7301 airfoil show that the unsteady pressure distributions agree well, whereas theunsteady lift and moment curves are not always in good agreement. 3D results are obtained with a 3D Full Potential code and a 3D time linearized TSD method for a swept NACA0012 wing and for the LANN wing, an AGARD standard test wing, both oscillating with small amplitudes. The agreement of the unsteady first harmonics of pressure distribution indicates that the time linearized approach may be sufficient for low amplitudes. For higher amplitudes, however, the appearance of pronounced higher harmonics (even for a wing with a conventional airfoil section) indicates strong nonlinear behavior combined with complicated shock motions.