Abstract:High-speed aircraft often develop separation-induced leading-edge vortices and vortex flow aerodynamics. In this paper, the discovery of separation-induced vortex flows and the development of methods to predict these flows for wing aerodynamics are reviewed. Much of the content for this article was presented at the 2017 Lanchester Lecture and the content was selected with a view towards Lanchester’s approach to research and development.
“…Both of them are in good agreement with Polhamus’ theory for AOA below approximately , which indicates the relative unimportance of viscous effects on the lift at these Reynolds numbers. Above differences increase, which is likely due to the complex vortical structures affected by the Reynolds number and the vortex breakdown (Luckring 2019). Figure 8.The steady asymptotic lift coefficient calculated by CFD for starting flow of a delta wing at different AOAs for , with comparison to Polhamus’ potential theory and Earnshaw & Lawford's experimental results.…”
Section: Application Of the Vortex Force Approach To The Starting Flomentioning
“…Both of them are in good agreement with Polhamus’ theory for AOA below approximately , which indicates the relative unimportance of viscous effects on the lift at these Reynolds numbers. Above differences increase, which is likely due to the complex vortical structures affected by the Reynolds number and the vortex breakdown (Luckring 2019). Figure 8.The steady asymptotic lift coefficient calculated by CFD for starting flow of a delta wing at different AOAs for , with comparison to Polhamus’ potential theory and Earnshaw & Lawford's experimental results.…”
Section: Application Of the Vortex Force Approach To The Starting Flomentioning
“…The fitting of the medians to a straight line gives the slops and 2.38 for | β | <3, 3 < | β | <6, and 6 < | β | <9, respectively. These values are below the typical value for low‐speed attached‐flow lift‐curve slope that, for , is around 4 (see Figure 5 in Luckring 31 ). The analysis of the drag coefficient (see panels D–F), besides showing the expected growth of C D with C L , highlights the important drag produced by the kite.…”
Section: Experimental Results For the Rfd Kitementioning
The aerodynamic characteristics of a leading edge inflatable (LEI) kite and a rigid‐framed delta (RFD) kite were investigated. Flight data were recorded by using an experimental setup that includes an inertial measurement unit, a GPS, a magnetometer, and a multi‐hole Pitot tube onboard the kites, load cells at every tether, and a wind station that measures the velocity and heading angle of the wind. These data were used to feed a flight path reconstruction algorithm that estimated the full state vector of the kite. Since the latter includes the aerodynamic force and moment about the center of mass of the kite, quantitative information about the aerodynamic characteristics of the kites was obtained. Due to limitation of the experimental setup, the LEI kite flew most of the time in post‐stall conditions, which resulted in a poor maneuverability and data acquisition. This assumption was corroborated by a particular maneuver where the lift coefficient decreased from 1 to 0.4, while its angle of attack increased from 35° to 50°. On the contrary, abundant flight data were obtained for the RFD kite during more than 10 figure‐eight maneuvers. Although the angle of attack was high, between 20° and 40°, the kite did not reach its maximum lift coefficient. High tether tensions and a good maneuverability were achieved. Statistical analysis of the behavior of the lift, drag, and pitch moment coefficients as a function of the angle of attack and the sideslip angle allowed to identify some basic aerodynamic parameters of the kite.
“…With increased computational power, research focused on the unsteady effects of a DW associated with vortex breakdown [3][4][5][6][7]. The breakdown is created by the shearlayer instabilities, which are responsible for the vortex bursting [21]. As the AoA of a DW increases, the leading edge vortex experiences a sudden axial deceleration inside the primary core.…”
Section: Research Framework and Backgroundmentioning
Supersonic flight for commercial aviation is gaining a renewed interest, especially for business aviation, which demands the reduction of flight times for transcontinental routes. So far, the promise of civil supersonic flight has only been afforded by the Concorde and Tupolev T-144 aircraft. However, little or nothing can be found about the aerodynamics of these aeroshapes, the knowledge of which is extremely interesting to obtain before the development of the next-generation high-speed aircraft. Therefore, the present research effort aimed at filling in the lack of data on a Concorde-like aeroshape by focusing on evaluating the aerodynamics of a complete aircraft configuration under low-speed conditions, close to those of the approach and landing phase. In this framework, the present paper focuses on the CFD study of the longitudinal aerodynamics of a Concorde-like, tailless, delta-ogee wing seamlessly integrated onto a Sears–Haack body fuselage, suitable for civil transportation. The drag polar at a Mach number equal to 0.24 at a 30 m altitude was computed for a wide range of angles of attack (0∘,60∘), with a steady RANS simulation to provide the feedback of the aerodynamic behaviour post breakdown, useful for a preliminary design. The vortex-lift contribution to the aerodynamic coefficients was accounted for in the longitudinal flight condition. The results were in agreement with the analytical theory of the delta-wing. Flowfield sensitivity to the angle of attack at near-stall and post-stall flight attitudes confirmed the literature results. Furthermore, the longitudinal static stability was addressed. The CFD simulation also evidenced a static instability condition arising for 15∘≤α≤20∘ due to vortex breakdown, which was accounted for.
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