Delta wing in transonic flow
Delta wing aerodynamics is vortex dominated. The delta wing planform geometry with leading edge sweep and un-swept trailing edge gives rise to interesting flow physics. The flow over the suction surface of the wing is dominated by spiral vortices that are stable at low to moderate angles of incidence but break down at high angles of attack. Leading edge flow separation over a delta wing creates a leading edge vortex that reattaches and then separates forming helical vortices. In the transonic flow regime, the presence of a part chord shock introduces shock-vortex and shock-boundary layer interactions. Vortex breakdown, transonic buffet, and transonic buffeting---in the case when the wing is flexible---are some of the phenomena that needs to be predicted and understood.
The vortical flow experiment -2 (VFE-2) delta wing
Medium radius leading edge
Leading edge sweep 65°
M = 0.85
Re = 6 x 106; AOA = 24.6°
RANS and URANS simulations
URANS simulations with Spalart-Allmaras turbulence model including compressibility and Edwards-Chandra corrections.
Coefficient of pressure contours show vortex breakdown downstream of x_r/c_r = 0.4. Two suction peaks due primary and secondary vortices. Crossflow and normal shocks present downstream of x_r/c_r = 0.4 along the root chord and spread across the suction surface of the wing.
Unsteadiness and boundary layer separation observed close to the trailing edge due to recompression caused by a series of shocks.
Mach contours shown on a streamwise planar section cut through the primary vortex. The vortex breakdown is clearly visible downstream of x_r/c_r = 0.4.
Adithya Mayya, Magan Singh, and Kartik Venkatraman (2023). Transonic shock vortex shock boundary layer interactions over a delta wing. In: 57th 3AF International Conference (AERO2023), Bordeaux, France, March 29-31, 2023.
Steady flow RANS simulations performed using SA and SST turbulence models. The vortex breakdown position moves downstream of x_r/c_r = 0.7. URANS simulations are therefore critical in order to predict vortex breakdown correctly.
Coefficient of pressure distribution along different sections on root chord. Vortex breakdown initiates between x_r/c_r = 0.7 and 0.8. Angle of attack 24.6 deg.
Above, vorticity contours on cross-sections along root chord. Vorticity breakdown is clearly seen. Below, streamlines over the suction surface.
Adithya Mayya, Tumkur Pradeepa Karnick and Kartik Venkatraman (2022). Shock vortex interactions and transonic buffet over a flexible delta wing in 2022 AIAA Aviation Forum, Chicago, IL, June 27-July 1, 2022. https://doi.org/10.2514/6.2022-4173.