Scale effects on a single-element inverted wing in ground effect

Abstract

A study was conducted on a GA(W)-1 wing in order to investigate the effect of testing inverted wings in ground effect at low Reynolds numbers. The wing was tested at a range of ground clearances and Reynolds numbers and results showed that the wing's performance was dependent on both these parameters. Surface flow-visualisation and numerical simulation results highlighted the existence of a laminar separation bubble on the wing's suction surface. The results also indicated that both the bubble's length and the onset of separation were sensitive to ground clearance and Reynolds number. Attempts were made to minimise the wing's Reynolds number dependency by using transition strips on the suction surface. The transition strip results highlighted the influence that a laminar separation bubble has on the overall performance of the wing and how its presence alters the force enhancement and reduction mechanisms on an inverted wing in ground effect.

Aerodynamic characteristics of a monoposto racing car front wing operating in high turbulence conditions

“…It must be assumed that bypass transition has occurred and the boundary layer is turbulent across the entire chord length, given the lack of evidence of either natural or separation-induced transition. The elimination of the bubble depicts similarity to the forced-transition results of Correia et al (15). The fact that the boundary layer is capable of negotiating the adverse pressure gradient without separating (to form the bubble) suggests that it must be turbulent because it cannot have more energy than the undisturbed case given the lower dynamic pressure in which it operates.…”

“…In the undisturbed case a laminar separation bubble, which is the boundary layer transition mechanism for the wing, is noticeable. This phenomenon was discussed previously by Correia et al (15). When operating in the wake, a separation bubble does not form and trailing-edge separation occurs in the centralsection.…”

“…The fact that the boundary layer is capable of negotiating the adverse pressure gradient without separating (to form the bubble) suggests that it must be turbulent because it cannot have more energy than the undisturbed case given the lower dynamic pressure in which it operates. Correia et al (15) also showed that the forcereduction region of the single-element version of the wing configuration tested here was due to an effective de-cambering of the wing due to the separation bubble shrinking. Thus, by the bubble being eliminated the force reduction mechanism has been avoided, hence the lack of the force reduction region in force results shown previously.…”

Characteristics of Boundary-Layer Transition and Reynolds-Number Sensitivity of Three-Dimensional Wings of Varying Complexity Operating in Ground Effect

“…Given that a wing operating in ground effect produces significantly lower pressures and stronger pressure gradients than its out-of-ground-effect counterpart, Reynolds number effects and the importance of transition could be even more important. Although some studies [9][10][11] have cited Reynolds number and transitional effects for ground-effect geometries, there is an overall lack of investigation into the subject. [ [11] Four configurations of three-dimensional double-element wings were examined by Jasinski & Selig [9] through force measurements and a wake study with a 7-hole pressure probe in a fixedground facility.…”

“…Although some studies [9][10][11] have cited Reynolds number and transitional effects for ground-effect geometries, there is an overall lack of investigation into the subject. [ [11] Four configurations of three-dimensional double-element wings were examined by Jasinski & Selig [9] through force measurements and a wake study with a 7-hole pressure probe in a fixedground facility. The work included testing the wings at a range of Reynolds numbers in addition to incidence angle and flap position.…”