Development of the Aerodynamic Design Tools & Processes for Formula-SAE - Ryan Ockerby 2015

Monash Motorsport Final Year Thesis Collection

The Final Year Thesis, is a technical engineering assignment undertaken by students of Monash University. Monash Motorsport team members often choose to conduct this assignment in conjunction with the team. 

These theses have been the cornerstone for much of the team’s success. The purpose of the team releasing the Monash Motorsport Final Year Thesis Collection is to share knowledge and foster progress in the Formula Student and Formula-SAE community.

We ask that you please do not contact the authors or supervisors directly, instead for any related questions please email info@monashmotorsport.com

SUMMARY

This project is aimed at improving Monash Motorsport’s aerodynamic package design process due to new rules and increasing time restrictions. To achieve this, faster solving computational fluid dynamics (CFD) simulations running in conjunction with highly complex cornering CFD simulations, quality wind tunnel modelling and data acquisition plus improved on-track testing were investigated.

The project was successful in that a 59% reduction in solve time for the symmetrical straight line CFD simulation from changing the domain size, model simplification and re-evaluating the convergence criteria. Post processing results have been streamlined with quicker state files and a more intuitive and fluent process of documenting on the Monash Motorsport’s Google Wiki has been implemented. The introduction of a stiffer rig and larger and higher quality ground plane which showed had flow coming through the undertray is a positive step towards correlation. Tripping the flow on the stationary wheel in the wind tunnel had excellent correlation with CFD and literature.

These successes helped Monash Motorsport design their aerodynamics package with greater confidence in results and allowed for a greater number of designs and investigations to be completed.

INTRODUCTION

Formula-SAE (F-SAE) is the largest international engineering design competition and is held in over 10 countries with over 500 teams participating. Students design, manufacture and test prototype open wheeled cars against other universities across seven events that test the vehicles performance, design, cost and business model in which points are totaled out of a possible 1000 to determine the overall winner. The Society of Automotive Engineers (SAE) set rules in which teams must design their car around to ensure safe vehicle design and close competition. 

Monash Motorsport, Monash University’s entrant, has been competitive in aerodynamic design in Formula Student since 2002. Aerodynamic performance through the use of aerodynamic components such as wings, underbody diffusers and bodywork has been a long-debated topic because of the low-speed tracks Formula Student competes on. Majority of the teams chose to run without additional aerodynamic components before 2013. Taking advantage of this through access to the Monash Wind Tunnel and knowledge of aerodynamic engineering, Monash won the past six Formula SAE-Australasian competitions and placed highly in competitions in the United Kingdom and Germany.

Since 2013, aerodynamic components are seen on the majority of teams competing. The increasing amount led SAE to change the rules regarding aerodynamic packaging space and mounting to prevent incidents with large wings failing and falling off the car whilst also challenging students to design from first principles. These rules meant that wingspan on the rear was reduced by over 40% and restricted height forward of the front wheels. In order for Monash to retain their aerodynamic advantage over their competitors, current and future designers of the aerodynamic components must ensure the design processes they use directly translate to performance on-track.

In order to score a significant increase in points over other competitors, a point simulator was created for the Monash F-SAE team (Webb, 2012). It was determined that a 10% increase in downforce would result in a 15 point increase out of 1000 available at the competition. 

Computational Fluid Dynamics (CFD) has been the main design tool used to develop aerodynamic components since 2011. This was driven by reduced wind tunnel testing time, shorter design periods and earlier build completion dates to enable the car to be set-up and ensure reliability for competition. The consequences of such design processes are that there is no ability to modify the design if wind tunnel and on-track testing show discrepancies against the CFD simulation results as the components have already been manufactured.

The new design process aims to incorporate all three major design tools into the design and allow for modification to manufactured components and data for future years and design events. A CFD simulation model that enables the designer to quickly change concepts and parameters in conjunction with a complex and high quality CFD simulation model ensures flow structures are consistent and accurate. Improving the wind tunnel model so it can correlate with CFD results will also help integrate the three tools. To achieve the desired design process, three aspects needed to be addressed: Reduction in solve time through domain dependence studies and model simplification to allow for more simulations to be completed during the design period Ensuring quality correlation between wind tunnel and on-track testing with CFD Implementing cornering simulations using asymmetric models and rotating reference frames to design the car for yawed flow.

CONCLUSION

This project aimed at improving Monash Motorsport’s aerodynamic package design process. To achieve this, quicker solving CFD simulations running in conjunction with highly complex cornering CFD simulations, better wind tunnel modelling and data acquisition and improved on-track testing were looked at.

The project was successful in a 59% reduction in solve time for the symmetrical straight line simulation from changing the domain size, model simplification and re-evaluating the convergence criteria. Post processing results have been streamlined with quicker state files and a more intuitive and fluent process of documenting the Monash Motorsport’s Google Wiki has been implemented. The introduction of a stiffer rig and larger and higher quality ground plane which showed had flow coming through the undertray is a positive step towards correlation. These successes helped Monash Motorsport design their aerodynamics package with greater confidence in results and allowed for a greater number of designs and investigations to be completed. Further development (pressure tapping, wind tunnel CFD, mesh refinements), most of which being conducted in the summer of 2015, will aid the team going into 2016 and beyond. This further development is required as there will always exist negative aspects to each part of the testing and constant evaluation of the design tools must be completed to ensure that there are many options available to the future designers.