Vortical flow prediction for the design of a wind tunnel experiment with a pitching lambda wing

Abstract

The IWEX wind tunnel model (Instationares Wirbelexperiment, German for: Unsteady Vortex Experiment) was developed to study vortical flow at static and oscillating angles of attack. Numerical computations were performed beforehand to study important aerodynamic aspects. The focus of this paper is on those results that were affecting the design of the model. The experimental concept of a new test rig, wind tunnel walls and the new half wing model is briefly described. The lambda wing has a purely round leading edge with a constant nose radius to chord ratio of 0.5 %. The flow characteristics of the main vortex, generated at the nose of the main wing, and the smaller tip vortex are specified. The inboard motion of the main vortex with increasing angle of attack and the consequences for the load distribution are described. The free stream Mach number range of the test envelope is from 0.3 to 0.7. Therefore, transonic effects, especially shock–vortex interactions triggering vortex development, had to be analyzed for a safe design of the model. A peniche was designed to minimize the differences of the flow character compared to reference results of the model without wind tunnel walls. The effects of corner separation and displacement are specified at different stages of the iterative process. Finally, basic results for a pitching motion are discussed, based on global and distributed coefficients.