ground-effectlisted

# Ground Effect (aerodynamics/ground-effects/ground-effect) Use when the task is wing aerodynamics in ground effect: induced drag reduction near the ground, the image vortex method, and the takeoff and landing consequences. ## Domain quick reference - Ground effect onset is roughly h / b < 1.5, where h is the height of the wing reference line above the ground and b the span; the effect strengthens as h / b shrinks. - Image vortex method: the ground plane is replaced by a mirror image of the wing vortex system, reflected across the ground and with circulation reversed. The image system lies 2 * h below the real system and enforces zero normal flow at the ground. Its upwash at the real wing cancels part of the downwash. - Induced drag reduction factor (image vortex result, elliptic loading): sigma = 1 / (1 + 16 * (h / b)^2). The induced drag in ground effect is C_Di,g = C_Di,inf * (1 - sigma), and the ratio to free-air value is 16 * (h / b)^2 / (1 + 16 * (h / b)^2). Example: h / b = 0.5 gives sigma = 0.2 (20 percent drag cut), h / b = 0.25 gives sigma = 0.5. - The induced angle of attack falls by the same factor (1 - sigma), which raises the effective aspect ratio to AR / (1 - sigma) and the lift curve slope toward the 2D value a_inf. - Lift at fixed angle of attack grows in ground effect; the lift-curve slope follows a_g = a_inf / (1 + a_inf * (1 - sigma) / (pi * AR)). - Takeoff: reduced induced drag shortens the ground roll and eases initial