Lift Enhancement of Circulation Control as Influenced by Ground Effect

Abstract

Circulation control and a lifting surface influenced by ground effect have both individually proven to augment the generation of lift. Recent research at West Virginia University has explored the feasibility of amalgamating the two phenomena, in an attempt to enhance each other. This effort experimentally explores the impact that operation in close proximity to the ground has on a NACA 0018 circulation control modified model in West Virginia University's Closed Loop Wind Tunnel. To simulate the ground, a plane of symmetry methodology was employed by including a second NACA 0018 circulation control modified model as a mirror image to the instrumented model. Since the models have identical geometries, along with the same blowing coefficients, the vertical velocities generated by the two models interact at the center and nullify each other, creating the symmetry plane. While there are many variables that influence the two phenomena separately, this effort only considers the impact the ground and the blowing coefficient has on the aerodynamic quantities. To create this effect, one of the models remains fixed while the other model varies at three designated distances, corresponding to an h/c value of 0.258, 0.646, and 0.984. This research effort demonstrates that with the constraints of zero angle of attack and low blowing coefficients, the combinataion of circulation control and ground effect detract from one another, in terms of L/D, however more research is necessary to explore the aforementioned constraints. Nomenclature A jet= area of the jet T plenum = temperature of the plenum b = wing span u(x) = horizontal velocity contributionlift coefficient out of ground effect γ = specific heat ratio of air C p = coefficient of pressure ΔP = local pressure differential C μ = blowing coefficient ρ j = density of the jet c = chord length ρ ∞ = free stream density H = height at the lowest point of the wing from the ground h/c = height from ground to chord length ratio h(x) = height of the lower surface of the airfoil h te = height of the trailing edge = mass flow rate P plenum = pressure of the plenum P ∞ = free stream pressure P = pressure at location x q,q ∞ = dynamic pressure R = universal gas constant T = thrust of the jet 1 Undergraduate Researcher, Mechanical and Aerospace Engineering, P.O. Box 6070, Student Member 2 Post-Doctoral Fellow, Mechanical and Aerospace Engineering,