Tip vortex/airfoil interaction for a low Reynolds number canard/wingconfiguration

Abstract

The effects of the vortical wake shed by a finite span canard on a low Reynolds number airfoil were examined. Aerodynamic performance was evaluated through direct measurements of lift, drag, and 1/4-chord pitching moment. Spanwise static pressure and surface film visualization data were also acquired. A reduction in the downstream airfoil drag coefficient and an increase in its lift/drag were noted in the presence of the canard for a wide range of configurations. Static pressure and surface visualization data provided indication of some of the boundary-layer characteristics responsible for the drag behavior. Nomenclaturewing chord length c c = canard chord length D =wing drag force L = wing lift force M =wing 1/4-chord pitching moment O c = canard offset, Z c /c P = static pressure q = dynamic pressure, -\/2(pU 1 ) R c = chord Reynolds number, -cU^/V S = nondimensional separation distance, =X c /c U^ -freestream velocity X c = stream wise distance between canard/wind 1/4-chord axes x = chordwise coordinate y -spanwise coordinate Z c = vertical displacement of canard 1/4-chord axis with respect to wing 1/4-chord axis a = wing incidence a c -canard incidence d c =declage, =(a c -a) e = down wash angle v = kinematic viscosity p = density

Stall Delay of Two-Wing Configurations with Decalage at Low Reynolds Numbers

“…Historically, biplane wings offered increased planform area and increased structural rigidity through inter-wing bracing. With the development of monoplane aircraft, biplane aircraft were largely relegated to sport aviation [7,8]. However, previous studies have demonstrated that two wing configurations can delay stall at low Reynolds numbers [1,9].…”

“…Several studies have considered the effects of decalage (differing wing angle: δ = α1 -α2) [7,10,11]. However, many of these studies only consider the effects at large gaps or stagger (typically fixed at or above one chord) missing the region of greatest potential improvement [1].…”

“…However, many of these studies only consider the effects at large gaps or stagger (typically fixed at or above one chord) missing the region of greatest potential improvement [1]. In addition, there is little information on the flow fields and with the limited number of variations in decalage it is difficult to gauge the significance of decalage from previous studies [7,10,11].…”

Blade Vortex Interactions: Experimental Measurements of the Near-Flow Field

“…The normal BVI is, however, of particular significance when the main rotor tip vortices pass through and normal to the tail rotor disk -a situation that exists under most flight conditions, which gives rise to an increase in tail rotor noise due to the main rotor/tail rotor vortex interaction see for instance, [7][8] . Normal BVI is also observed when the vortical wake shed by a finite span canard impinges on a wing 9 . The majority of the research, however, has been performed for the case of main rotor BVI where the vortex interacts with another main rotor blade 11 .…”

On the secondary stall of a wing in tandem configuration

“…Specifically, they have explored wings encountering wakes characterised by various vortical structures that differ in strength, orientation (both parallel and perpendicular), wavelength, frequency and length scales. These studies have analysed how such wake disturbances alter the aerodynamic response and performance of the downstream wing [4,[10][11][12][13][14][15]. However, there has been more limited investigation into the upstream effects of a rear wing on the aerodynamics of a forward wing and the wake interactions between them.…”