Critical states and flow structure on a 65-deg delta wing

Swept and delta wings maneuvering at moderate and high angles of attack produce highly nonlinear and often discontinuous aerodynamic forces and moments that are difficult to model. The nonlinear indicial response (NIR) methodology and the concept of critical states accompanied by changes in the flow structure and topology could provide a rational framework for the analyses and modeling of these flows. The analysis of surface oil-flow photographs and laser light sheet high-speed video images of smoke flow has been performed. The correlation of the structural and topological changes in the flow with force and moment data follows. Critical states are often accompanied by changes in the flow topology and not all topological changes produce measurable changes in the forces and moments, however, a useful relationship may exist.