Self-adaptive elastic flaps with bending and torsion for 3D blunt body drag reduction Camacho Sánchez, J.M Lorite Diez, M. Fan, Y. Jiménez-González, J. I. Cadot, O. Aerodynamics Flow-structure interactions Turbulence This study investigates the potential for drag-reduction of low-mechanical-order, self-adaptive control systems, consisting of hinged flaps attached along the edges of the rectangular base of a canonical blunt body. Comparative experiments are conducted in a wind tunnel under cross wind conditions at a Reynolds number of Re = 2.13×10 5. The flaps, made of rigid rectangular panels, are mounted in three configurations: rigidly fixed , flexibly hinged with a single degree of freedom in bending , and flexibly hinged with two degrees of freedom, allowing both bending and torsion , the latter representing a novel drag-reduction device, easily tunable to ensure a quasi-steady, stable adaptive reconfiguration. Two geometric arrangements are tested: horizontal f laps attached along the top and bottom (TB) edges, and vertical flaps along the lateral (left and right, LR) edges. The experimental study includes force, pressure, flap deformation and wake ve locity measurements at varying yaw angles to simulate crosswind conditions. When the body is aligned with the flow, both arrangements reduce drag due to a rear cavity effect that elongates the recirculating flow. The TB arrangement is found to be much more effective at reducing drag in yawed conditions and its performance is improved using the flexible hinges. In these cases, static deformations correspond to boat-tailing that reduces the induced drag together with the turbulent kinetic energy in the wake. The use of the wind-average drag coefficient (taking into account events of crosswind) to evaluate an effective drag reduction clearly shows the TB arrange ment with bending and torsion as the best appendage, with a 7.62% drag reduction compared to the body with no appendages, proving the good performance of sim 2026-04-08T10:54:05Z 2026-04-08T10:54:05Z 2026-07 journal article Camacho-Sánchez, J. M., Lorite-Díez, M., Fan, Y., Jiménez-González, J. I., & Cadot, O. (2026). Self-adaptive elastic flaps with bending and torsion for 3D blunt body drag reduction. Journal of Fluids and Structures, 144(104560), 104560. https://doi.org/10.1016/j.jfluidstructs.2026.104560 https://hdl.handle.net/10481/112692 10.1016/j.jfluidstructs.2026.104560 eng info:eu-repo/grantAgreement/EC/FP7/TED2021-131805B-C22 http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier