Scale resolving simulation of buffet effects induced by UHBR nacelle installation

Abstract

The integration of large engine nacelles below the wing of an aircraft is accompanied by aerodynamic effects such as unsteady shock buffet occurring on the lower surface of the wing. In this study these effects are investigated by applying a hybrid RANS-LES method on a commercial transport aircraft configuration. A local region on the inboard wing lower surface is thereby simulated using an IDDES approach allowing a detailed assessment of the interaction of the transonic shock with the turbulent boundary layer while the remaining computational domain is simulated using a RANS method. To allow a smooth transition between the RANS and the LES region a synthetic turbulence generator is located upstream of the shock. Here we show that the IDDES approach accurately computes the wing lower surface buffet effects. Comparisons with wind tunnel experiments show excellent agreement in terms of local pressure distributions and pressure fluctuations on the wing lower surface around the shock and a significant improvement of the simulation accuracy compared to conventional approaches based on pure RANS modeling. Spectral analysis of the unsteady shock motion supports previous findings that the lower wing buffet phenomenon is associated with Strouhal numbers in the range of 0.2 to 0.4.