Formula Student is a global engineering competition where university students collaborate to design, construct, and race formula-style cars. Aerodynamics is one aspect in the vehicle design that can improve on-track performance by increasing cornering and straight-line speed. To improve the aerodynamics of KTH Formula Student's DeV18 vehicle, the side structure is being redesigned. The current model, DeV17, features an underperforming tunnel-based side structure. To address this issue, this had the goal to investigate a new multi-element wing design that utilizes ground effect. The design study of the DeV18 vehicle is conducted using Siemens NX 2212 for 3D modelling and Simcenter Star-CCM+ 17.06.008-R8 for airflow simulations. To quickly investigate certain design parameters effect on the results, Design Manager Project inside Simcenter Star-CCM+ is used. The resulting side structure produces a total of 26 N of downforce and 6 N of drag at 40 kph, more than twice that of DeV17’s side structure while also producing less drag. Although this significant improvement compared to DeV17, it is believed that further increases in performance are necessary to compete with top teams. By using a more sophisticated method to optimize the multi-element wing, such as adjoint optimization, the concept could be improved. However, the overall potential of the concept is still considered too limited to achieve the desired performance goals, which is why it will no longer be investigated further.

This bachelor thesis aims to describe the work performed for the design of the undertray for the Kungliga Tekniska Högskolan Formula Student(KTHFS) race car. The goal was to achieve an aerodynamically optimized undertray design that follows the regulations of the competition and the targets set by KTHFS concerning the weight, the size, the materials needed for its manufacture and costs. After some research on previous work, the concept, on which we decided that the undertray would rely on, is Venturi tunnels inspired by the Aston Martin Valkyrie, chosen for its ability to provide a large amount of downforce with a negligible amount of drag using ”ground effect”. Numerous CAD design models were created in Solid Edge and a finalized design was then ported over to Siemens NX to be analyzed using Star-CCM+ and its Design Manager feature. The CFD analyses and optimization was performed in Star-CCM+ with regards to pressure gradient, streamline velocity and downforce. These were done with variable parameters in areas such as expansion height, inlet area and ride height. Contained within this report is a more detailed description of how the CFD analysis was performed as well as suggestions for manufacturing said undertray. Given the time constraints and the societal impacts of COVID-19, manufacturing had to be removed from the scope of the project, however, a step-by-step manufacture guide is provided within. Analysis of uur final design showed 428 N of downforce, a weight of 2.55 kg and a production cost of approximately 2320 SEK. It therefore passes the requirements for weight, cost and ride-height rule regulations set by Formula Student and internal KTHFS targets. / Detta kandidatexamesarbete syftar till att beskriva arbetet som utförts för konstruktionsdesignen av Kungliga Tekniska Högskolan Formula Student (KTHFS) racerbils underrede. Målet var att uppnå en aerodynamisk optimerad underredes design som följer de regler och krav fastställda av KTHFS gällande vikt, storlek, material som behövs till tillverkningen och kostnader. Efter en litteraturstudie på tidigare arbete, blev Venturi tunnlar, inspirerade av Aston Martin Valkyrie, konceptet som vi beslutade att uderreden skulle bygga på och valda på grund av deras förmåga att förbättra bilens prestanda genom sitt nedkraftsbildande och försumbar mängd drag med hjälp av ”ground effect”. Många CAD-designmodeller skapades i Solid Edge och en slutgiltig design överfördes sedan till Siemens NX för att analyseras med Star CCM+ och dess Design Managerfunktion. CFD-analyserna och optimeringen utfördes i Star CCM+ med avseende på tryckgradient, strömlinjehastighet och nedkrafter. Dessa gjordes med variabla parametrar i områden som utvidgningshöjd, inloppsarea och frigångshöjd. I denna rapport finns en mer detaljerad beskrivning av hur CFD-analysen utfördes samt förslag för tillverkning. Med tanke på tidsbegränsningarna och samhällseffekterna av COVID-19 fick vi ta bort tillverknink från projektets omfattning, men en steg-för-steg tillverkningsguide tillhandahålls i rapporten. Analyser av vår slutgiltiga design visade på 428N downforce, en vikt på 2,55 kg och en produktionskostnad på cirka 2320 SEK. Den överenstämmer därför kraven för vikt, kostnad och frigångshöjd som fastställdes av Formula Student.