Flow-field interference produced by an asymmetrical support strut

The interference flow field associated with an asymmetrical strut-mounted aircraft model was studied visually and through floor pressure measurements in a low-speed wind tunnel. The work was undertaken to shed light on the unsteady interference phenomena which are expected to prevail in oscillatory tests. The conditions under which direct support interference and coupled supportl/wall interference could occur were explored qualitatively. Static support interference was found to be significant at incidence angles below about 20°, and wall interference, above this angle. Coupled support/wall inteference is expected to be larger in pitch oscillation than in roll oscillation tests. This unsteady interference is expected to peak at intermediate incidence angles near 28°. These findings are generally applicable to test installations involving similarly-sized models in closed, low-speed wind tunnels.