Modern materials and manufacturing technologies have allowed the construction of morphing wings that are able to continuously vary certain airfoil parameters such as twist, camber, or control surface deflection as a function of span. This work presents a twist effectiveness parameter as a means of comparing the ideal aerodynamic efficiency of spanwise continuous control surfaces (morphing wings) and spanwise discrete control surfaces (standard wings). A numerical algorithm is used to compute the twist effectiveness of both continuous and discrete control-surface designs over a wide range of planform shapes with evenly spaced actuation for inviscid, incompressible flow. Results included here show that using continuous control surfaces instead of discrete control surfaces reduces induced drag by less than 5% for most applications.

When a flying wing comes within close proximity to the ground, a phenomenon called ground effect occurs where the lift is increased and the induced drag is decreased. This research seeks to determine the optimal dihedral distribution predicted by lifting-line theory that minimizes induced drag in ground effect. Despite some limitations, using lifting-line theory for this study allows for quick results across a large range of design variables, which would be infeasible for high-fidelity methods. The SLSQP optimization method is used along with a numerical lifting-line code to find the dihedral distribution that minimizes induced drag. Results are presented showing how the wing height, taper ratio, lift coefficient, and aspect ratio impact the induced drag and optimal dihedral distributions. For a given geometry, lifting-line theory predicts that there is a certain height above ground where the optimal solutions for a wing below this height result in bell-shaped wings with large section dihedral angles corresponding to a significant induced-drag reduction. For example, a wing with $R_A=8$ and height of $h/b=0.25$ can benefit from a reduction in induced drag of nearly 50% by employing an optimal dihedral distribution compared to a wing with no dihedral distribution.