Applicability of non-circulatory loads under extreme separation

Determine whether all non-circulatory force and moment contributions in the attached-flow formulation, particularly the effective torsional-rate contribution, remain applicable at very large angles of attack or should be modified or disabled, with the aim of improving modeling of stall-induced vibrations in wind turbines under standstill conditions.

Background

The paper develops a complete attached-flow formulation for unsteady airfoil aerodynamics, including circulatory shed-wake dynamics and non-circulatory added-mass force and moment contributions, for use in generalized lifting-line wind-turbine solvers. Its derivation and verification concern attached flow and the ideal thin-airfoil limit, whereas fully separated flow remains outside the principal scope of the formulation.

In the current implementation, attached-flow circulatory dynamics are disabled once the airfoil is fully separated, but the non-circulatory force and moment contributions are retained. The authors explicitly identify the unresolved issue of whether those contributions—especially the effective torsional-rate term—remain physically and numerically appropriate at very large angles of attack, or whether they require modification or removal. Resolving this issue could improve predictions of stall-induced vibrations, particularly during wind-turbine standstill conditions.