Three-dimensional pseudo-unsteady viscous-inviscid interaction for wings in transonic flow

Aircraft aerodynamic and aeroelastic optimization is applied increasingly often at the
preliminary design stage. Performing such optimizations involves many design variables
and higher-fidelity solutions of the Reynolds-Averaged Navier-Stokes equations have significant
computational cost that is incompatible with repeated application. The tools
used to assess the aerodynamic quality of a design within an optimization framework
must be computationally efficient. The present work introduces a viscous-inviscid interaction
methodology in three dimensions whereby inviscid solutions of the full-potential
equation are coupled with a viscous solver based on the integral boundary layer equations.
A novel pseudo-unsteady approach is used to ensure numerical stability when
considering mildly separated flows and shock waves in the transonic regime. The solvers
are coupled through a strip-based methodology in which chordwise boundary layer sections
are defined independently of the inviscid unstructured mesh on the surface of the
wing. The present methodology is demonstrated for transonic flow over the ONERA
M6 and LANN wings. Results show good agreement with reference data on the inboard
sections while some discrepancies between the present methodology and higher
fidelity data exist in the outboard region of the wings. The methodology is shown to
be computationally efficient and suitable for use in an optimization framework.