Adam FeneleyMotorsport Engineering MEng
Sidepod Design for the BR-14 Formula Student Car
Brunel racing has been entering a single-seat racing car into the Formula Student competition annually since 1999. These cars compete against others of academic institutions; racing at international locations such as the Silverstone and Hockenheim Grand Prix circuits, in Britain and Germany respectively. This project involved the design of the sidepods for BR-14, the 2013 entry into the Class A competition. In addition to the design, the project also involved study into carbon fibre materials and manufacture, as well as considerations for the physical wind tunnel testing of a scale model. Beginning with 3 concepts, a unique dual layer design was produced; instead of a single wall, two surfaces were used to allow independent internal and external curvature. This allowed airflow to be manipulated internally and externally with little interdependence. This innovation meant internal airflow could be slowed and kept stable for optimal cooling without flow separation. Simultaneously, drag could be reduced and a small amount of downforce created, by manipulating the external geometry and utilising aerodynamic ground effects. ANSYS was used to simulate the final design in a 3D CFD environment (using FLUENT code) to obtain results for velocity and pressure distribution throughout the sidepod. The geometry could then be tweaked to produce optimal internal and external flow profiles. Using guidelines from the producers of the CFD software, best practice guidelines were obtained for automotive aerodynamic studies. Following these guidelines allowed an optimal meshing setup to be produced, and ultimately resulted in convergent solutions. The simulation was modelled to pay close attention to flow behaviour close to the walls, so flow separation and turbulence generation could be more accurately predicted. Once the final design had been optimised in the virtual environment it was possible to test material suitability. Using the maximum pressure values from CFD, FEA (finite element analysis) was conducted within the ANSYS software. This produced material deflection and stress results, confirming that CFRP (Carbon fibre reinforced polymer) materials would be more than sufficient in this case. Test pieces of different thicknesses were also produced by the time to test the density of the material once fired in an autoclave. In industry, racing teams like those in Formula One competition rarely rely on purely this form of testing when it comes to flow analysis and material testing. However, in recent years, cars like Virgin Racing's VR-01 (now Marussia F1 Team) were produced using only CFD testing and no wind tunnel verification. In the past no wind tunnel verification had been conducted in time for competition with Brunel Racing. Subsequently, initial research was undertaken into how scale wind tunnel testing could be conducted in the future, and lists of components were drawn up to measure and log data. Brunel Racing have the ability to produce CFRP parts for the car body, and have been doing so for a number of years. Moulds are created out of high-density foam using CNC machines; cut directly from CAD models, so perfect geometry can be achieved. Sheets of pre-impregnated carbon fibre can then be layered up onto the mould and fired in an autoclave to set. BR-14 will have its body sections, sidepod and nose cone produced in this manner; with a smooth surface finish and the ability to add paint, decals and sponsors onto the surface of the vehicle.