Journal of Aerospace Engineering

The increasing demand to employ sharp-edged geometries in airframe design of advanced fighters to meet stealth requirements has nudged research to explore the new aerodynamic and dynamic characteristics of such configurations. In this paper, the wing rock oscillation is numerically simulated for a generic wing-body model consisting of cropped delta wing of 65°-sweep and chine-shaped forebody. The purpose is to develop a complete understanding of the complex flow interactions that drive the wing rock oscillation. The numerical simulation is based upon coupling the unsteady Euler fluid dynamic equations with the rigid-body dynamic equations in roll. A subiteration algorithm is employed to simultaneously solve the coupled equations. The numerical model exhibits a limit cycle oscillation in roll at an angle of attack of 35° with 16° peak-to-peak amplitude in roll angle. The complex interactions of the forebody-induced flow and the wing leading-edge vortices during wing rock are fully investigated and visualized. Analysis of the observed vortex breakdown dynamics during one entire cycle of the oscillation is also presented.

Numerical models of single-fastener bolted lap joints are developed in which the effect of the head angle and height on joint elongation are studied for three fastener sizes, three panel materials, and several panel thicknesses. Baseline 100° bolt-head angle numerical models are calibrated and validated with experimental data. These baseline models are then modified to predict the load-elongation behavior of lap joints with five different head angles and four different head heights. The numerical predictions are summarized in graphical form. The results show that the fastener head height has a much greater influence on joint-slip resistance than does the angle, with the shallower heads providing the greatest resistance to joint elongation under load.

A study is made of the variability of the response of stiffened composite panels, associated with variations in the major geometric and material parameters of the structures. The major parameters, which have the most effect on the response quantities of interest, are identified by using a hierarchical sensitivity analysis. The range of variation of the response is determined by using a fuzzy set analysis, with the major parameters treated as fuzzy parameters. Numerical results are presented showing the variability of the response of panels with both continuous and terminated stiffeners associated with variations in the micromechanical, effective layer, and geometric parameters. Both flat and curved panels are considered.