Reynolds Number, Compressibility, and Leading-Edge Bluntness Effects on Delta-Wing Aerodynamics
An overview of Reynolds number, compressibility, and leading edge bluntness effects is presented for a 65 degree delta wing. The results of this study address both attached and vortex-flow aerodynamics and are based upon a unique data set obtained in the NASA-Langley National Transonic Facility (NTF) for i) Reynolds numbers ranging from conventional wind-tunnel to flight values, ii) Mach numbers ranging from subsonic to transonic speeds, and iii) leading-edge bluntness values that span practical slender wing applications. The data were obtained so as to isolate the subject effects and they present many challenges for Computational Fluid Dynamics (CFD) studies.
Flow field study on a 65-deg blunted delta wing
The distinguishing feature of the delta wing is characterized by leading edge vortices which cause highly nonlinear forces and moments. At a sufficiently high angle of attack these vortices breakdown over the surface and introduce an additional transient in the aerodynamics. The understanding of aircraft aerodynamics with separated flows over the wing will permit design for increased maneuverability in future aerospace vehicles. Here, experimental and numerical investigations are carried out to obtain the complex flow field features on a 65° delta wing. Experiments are conducted at a nominal speed of 20m/s and Reynolds number of 2×10^5 at low subsonic wind tunnel facility. The qualitative techniques of oil flow visualization and tuft flow visualization and quantitative techniques of static pressure measurements have been used to observe various features of flow field. The angle of attack and side slip angle were varied in the range from 5° to 40° and 0° to 20° respectively. The effect of angle of attack, side slip, and speed variation on surface pressure and the effect of angle of attack on approximate vortex breakdown location were captured. Three dimensional numerical simulation were performed using the commercial software FLUENT over the delta wing. At the high angle of attack the major part of the flow over the wing is affected by vortex breakdown and vortex breakdown is asymmetric in nature. Side slip causes a strong asymmetry on the surface flow and pressures.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).