Design, construction, and testing of alow-cost aerodynamic force measurement system for a subsonic wind tunnel

Abstract

This work presents the design, construction, and experimental assessment of a low-cost external aerodynamic force measurement system for a subsonic wind tunnel. Aiming to overcome the prohibitive costs of commercial instrumentation in engineering education, the project developed a customized solution prioritizing structural integrity and maintenance feasibility. The construc tion methodology adopted a rigid welded steel architecture to minimize mechanical deflection and hysteresis, integrated with modular bending beam load cells to allow for sensor scalabi lity. The system characterization comprised static calibration, which confirmed high linearity (𝑅2 ≈ 1.0)andstable zero offsets, followed by aerodynamic testing using cylinders and a NACA 0012 airfoil. Results established a reliable operational envelope for freestream velocities excee ding 10 m/s, where the signal-to-noise ratio becomes optimal. A comparative analysis between 25 mm and 100 mm cylinders demonstrated the critical impact of wall confinement: the larger model exhibited overestimated drag coefficients due to a 21.6% blockage ratio, while the 25mm specimen yielded results consistent with subcritical literature (𝐶𝐷 ≈ 1.18). Furthermore, the system successfully resolved finite wing effects on the airfoil, capturing the induced drag penalty. It is concluded that the proposed architecture provides a robust, modular platform for educational and applied research, provided that geometric boundary conditions are respected.