![]() Upstream of the slot, crossflow disturbances are not significantly amplified (N ≪ 1) for Λ ≤ 20 ◦. At Λ = 35 ◦, the most amplified, steady and unsteady disturbances achieve N-factors in excess of 6 and 8, respectively. ![]() Crossflow-velocity profiles emerge for non-zero sweep, which, upon computing the N-factors with neutral points closest to the slot entrance, have a stabilizing effect on the disturbance amplification in the slot that is monotonic with sweep. ![]() As a consequence, for Λ = 0 ◦, large disturbance amplification in the slot can be uniquely attributed to the Görtler mechanism N-factors in excess of 12 are achieved at the trailing edge of the fore-element of the airfoil. Sweep angles from Λ = 0 ◦ to 35 ◦ are considered and the angle of attack is fixed at a relatively large 2.25 ◦, which maximizes the potential for crossflow instability on the bottom side of the airfoil and stabilizes the Tollmien-Schlichting instability. Disturbance amplification factors (N-factors) are computed with Linear Parabolized Stability Equations (LPSE) and both the most amplified, steady and unsteady solutions are identified. The laminar boundary-layer flow is resolved using an infinite-wing, invis-cid pressure distribution provided by MSES in combination with the boundary-layer solver DEKAF. The present work characterizes the linear instability mechanisms on the bottom surface of the X207.LS airfoil for conditions corresponding to the Klebanoff-Saric wind tunnel to use as reference for experimentation and future non-linear stability studies. By artificially tripping the boundary layer ahead of the slot, previous studies predict a large increase in drag due to the Görtler instability. Slotted, natural-laminar-flow airfoils feature a surface with concave curvature, in the slot in particular, which causes Görtler disturbances to be amplified in the boundary layer. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |