Motorcycle Aerodynamic Performance Improvement through Belly Pan Designs Evaluation and Testing

This paper presents a combined experimental and numerical study of motorcycle aerodynamic performance through belly pan design and improvement process. A 1/6^th scale motorcycle model was adopted and tested in a closed-return low-speed wind tunnel. Due to the light weight of the scale model, a test platform with an innovative method to balance and obtain measurement data was proposed and applied that overcame the difficulties of using the normal method of hanging the model from a strut. Prior tests were performed through a careful calibration process against benchmark data. A CAD model was also re-constructed and flow simulations using computational fluid dynamics (CFD) were performed. Based on wind tunnel tests and CFD simulations of the baseline model, it was found that the flow around the low-section of the vehicle between the front and the rear wheels was highly non-uniform due to geometry variations and ground effects. This suggests the introduction of a belly pan design, following the concept of a fairing, which might be able to reduce aerodynamic drag. A total of four belly pans have been designed and tested. Wind tunnel test measurements such as drag and down forces were taken and the data were used to compare the CFD calculations. Flow visualizations were also carried out by cotton strings and smoke techniques. It was found that the use of a belly pan improved the motorcycle aerodynamic performance by reducing the drag force in a range of 7.69% - 14% at an air speed of 34 m/s.