Design and development of a 1-DOF active flap system for high-performance motorcycles

Abstract

In recent years, aerodynamics has become a key factor in motorcycle engineering, contributing not only to performance enhancement but also to vehicle stability and safety. However, current fixed-geometry aerodynamic solutions inherently represent a compromise, being optimized for specific operating conditions while often penalizing others. To address this limitation, this study proposes the design and numerical validation of a 1-DOF active aerodynamic flap system for high-performance motorcycles. A complete design workflow is presented, starting from 2D airfoil selection and TRIZ-based conceptual development, up to CAD implementation and three-dimensional CFD validation. The system is evaluated under three representative riding scenarios: straight-line motion, cornering, and high-speed braking. All simulations are performed using the Dassault 3DEXPERIENCE CFD environment, ensuring consistent numerical modeling and design integration. The results show that the proposed system achieves near-aerodynamic neutrality in straight-line conditions, avoiding top-speed penalties typically associated with fixed aerodynamic appendages. In cornering conditions, the system provides moderate but beneficial aerodynamic assistance during transient phases. Under braking, the active flap delivers a significant increase in vertical load with a limited drag penalty, improving front-end stability and braking performance. A comparative analysis against conventional fixed-wing configurations demonstrates the advantages of scenario-adaptive aerodynamics in terms of performance flexibility and efficiency. In addition, actuator sizing and dynamic response analysis confirm the feasibility of real-world implementation within current motorcycle electronic and mechanical architectures. The study therefore demonstrates the viability of a compact, single-degree-of-freedom adaptive aerodynamic system that combines aerodynamic efficiency, mechanical simplicity, and integration feasibility for production-oriented motorcycles.