Sensitivity Analysis of Transonic Flow over J-78 Wings

Abstract

3D transonic flow over swept and unswept wings with an J-78 airfoil at spanwise sections is studied numerically at negative and vanishing angles of attack. Solutions of the unsteady Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver on unstructured meshes. The numerical simulation shows that adverse Mach numbers, at which the lift coefficient is highly sensitive to small perturbations, are larger than those obtained earlier for 2D flow. Due to the larger Mach numbers, there is an onset of self-exciting oscillations of shock waves on the wings. The swept wing exhibits a higher sensitivity to variations of the Mach number than the unswept one.

Aeroelastic Analysis of Wings in the Transonic Regime: Planform’s Influence on the Dynamic Instability

“…Several works try to represent pressure and lift distributions. In these cases often the numerical results agree very well with the experimental data [9][10][11]. On the other hand, if the objectives include a realistic estimation of the drag for wing models or for complete aircraft configurations, the research also requires a large amount of human and computational resources [12][13][14].…”

“…For Case 2, Figures 13 and 14 show the displacement time histories at the control node of the two wings calculated only for the cruise flight condition (ℎ = 10000 m). It is well known (see [11] or [23]) that approaching the transonic regime, for a fixed value of the angle of attack, because of the strong interaction between the shock wave and the boundary layer, the lift of rigid profiles tend to be reduced when the Mach number increases. This, in addition to the threedimensional effects generated by the sweep angle, reduces the lift coefficient of the wing (if the angle of attack at the root section is fixed, as in the present analyses).…”