A novel technical solution for using the magnetic levitation technique to measure skin friction drag

Abstract: In recent decades, several studies have focused on developing methods to reduce skin friction drag, as skin friction contributes substantial energy consumption in public transportation, leading to decreased fuel efficiency. However, due to the limitation on the flow velocity that can be achieved in wind tunnels and the Reynolds number attainable in lab conditions, the skin friction drag acting on test objects is often minimal compared to other external forces, such as the static friction between support surface and the test object. To overcome the challenge of measuring skin friction drag in a lab environment, this study employs magnetic levitation techniques to create a suspension system capable of generating a contactless condition, thereby eliminating the influence of external forces on skin friction drag measurements. Through the development and simulation of this system, the characteristics of magnetic force generated by electromagnets in both axial and radial directions were investigated. When a radial force is applied, it mimics the skin friction drag encountered in wind tunnel testing, and a restoring radial magnetic force is generated due to misalignment between two co-axial magnets. By analysing current variations within the maglev system, this study proposes a novel, accurate and contactless method for measuring skin friction drag. Keywords: Skin friction drag, Drag measurement, Fluid mechanics, magnetic levitation technique, Electromagnetic force