Design and testing of a rear wing for a Formula Student car

Tese de mestrado integrado, Engenharia Física, 2022, Universidade de Lisboa, Faculdade de CiênciasFormula Student teams go to extreme lengths to develop their aerodynamic packages, as it is a key factor to enhance car performance. The yearly objectives for the aerodynamic department are usually supplied by the vehicle dynamics department through lap time simulations. However, these usually are not capable of relating car attitude to aerodynamic performance and do not assume any relation between the aerodynamic coefficients. A simple aerodynamic model relating the lift coefficient to the drag coefficient and mass was added to the point mass simulator from the FST Lisboa vehicle dynamics department, to estimate the ideal aerodynamic coefficients and maximize vehicle performance for the current car design. By applying the results from the upgraded point mass simulator, a maximum theoretical lift, drag and mass were obtained. Through these results, a new rear wing concept, based on using airfoils as endplates was adopted, in order to create a design that would suit the new aerodynamic targets. Initially a low drag design was tested, however, preliminary results showed that due to high car mass it was not a viable design choice to follow. The final choice was to develop a high downforce rear wing. The resulting design was then validated using IST’s aeroacoustic wind tunnel, to assess its on-track performance. During this test, the aerodynamic forces applied on the whole vehicle were measured. A qualitative analysis of the results showed that the numerical simulations captured the experimental trends. Wool tufts were used as a flow visualization technique, these showed some discrepancies between the CFD simulations and experimental results, which were attributed to the simplifications made in both the numerical and experimental models. The implementation of the new aerodynamic model proved effective, as a design which yielded increase performance was obtained. Correlation between the CFD and on-track results is still limited due to modelling limitations in both experimental and numerical domains

Desenvolvimento e otimização de um dispositivo aerodinâmico para o carro do Formula Student UA

The development and optimization of the rear wing of a Formula Student car must be done with the aid of CFD numerical simulations, since in order to ensure a good aerodynamic performance a great number of wing configurations need to be tested. The aim of this thesis was to develop a fully functional optimization code, that could be easily adapted to generate the optimal rear wing for any given Formula Student car, only needing the car CFD results. As a means to accomplish that, a CFD simulation was performed to the Formula Student Aveiro teams’ car and additional wind tunnel testing was conducted with the purpose of corroborating the simulation results. Hereupon, the velocity profile at the car rear end, obtained in the CFD simulation, was used as the inlet in the rear wing simulation for the optimization process, allowing a contribution of the car geometry to the rear wing optimization without the addition of unnecessary computational time. Finally, an optimization code based on the Harmony Search Algorithm was created to define the optimal rear wing parameters and with that achieve an optimized rear wing configuration. The optimized configuration consists of 4 airfoils, and showed excellent results even surpassing the rear wing performance of the 2016 FSAE Czech Republic competition winner.O desenvolvimento e otimização da asa traseira de um carro do tipo Formula Student devem ser tratados através de simulações numéricas do tipo CFD, dado que, para assegurar uma boa performance aerodinâmica da asa traseira, teriam de ser testados um grande número de configurações. O objetivo deste trabalho era desenvolver um código de otimização¸ completamente funcional, capaz de ser facilmente adaptado, de forma a gerar uma asa traseira ótima para qualquer veículo do tipo Formula Student, sendo apenas necessários os resultados da simulação CFD. De forma a cumprir o proposto, foi realizada ao carro da equipa de Fórmula Student da UA uma analise CFD, tendo, adicionalmente, sido efetuados testes no túnel de vento com o propósito de corroborar os resultados da simulação. Tendo em consideração o exposto, o perfil de velocidades na parte traseira do carro, obtido através da sua simulação CFD, foi usado como Inlet na simulação da asa traseira para o processo de otimização, permitindo a contribuição da geometria do carro para o processo de otimização da asa traseira sem a adição de tempo computacional desnecessário. Por fim, foi criado um código de otimização baseado no Harmony Search Algorithm, com o propósito de otimizar os parâmetros que definem a geometria da asa traseira e com isso obter com uma configuração otimizada. A configuração otimizada e composta por 4 airfoils, tendo demonstrado excelentes resultados, ultrapassando até o desempenho da asa traseira da equipa que ganhou a competição FSAE Czech Republic, em 2016.Mestrado em Engenharia Mecânic

Aerodynamic study of the evolution of a Formula 1 front wing with the change in regulations between the 2021 and 2022 seasons

The objective of this final degree thesis is to comprehensively analyze and compare the evolution of the 2021 and 2022 front wings in the context of Formula 1. This study combines theoretical insights into fluid dynamics and Computational Fluid Dynamics (CFD) with an examination of the historical development of the sport, focusing specifically on front wing design. The thesis begins by providing a theoretical introduction to fluid dynamics and CFD, establishing the foundation necessary to understand the principles governing the aerodynamics of Formula 1 vehicles. Furthermore, a historical overview of Formula 1 is presented, highlighting key milestones and technological advancements that have influenced front wing design throughout the years. To conduct a thorough analysis, the two front wings are visually compared, allowing for a preliminary assessment of their differences in terms of shape, features, and design philosophy. Subsequently, four CFD simulations are carried out, enabling a more detailed evaluation of the aerodynamic performance of each front wing variant. The results obtained from the CFD simulations are analyzed and interpreted to extract meaningful conclusions. The impact of the regulatory changes implemented in 2022 on the aerodynamic behavior of the front wings is thoroughly evaluated, shedding light on the effectiveness of these modifications in reducing turbulence and enhancing overall performance. The conclusions drawn from this study provide valuable insights into the evolution and comparative performance of the 2021 and 2022 front wings. The findings not only contribute to a deeper understanding of the aerodynamic characteristics of these components but also offer valuable guidance for future design iterations. The present thesis aims to bridge the gap between theoretical knowledge and practical application by utilizing CFD simulations as a powerful tool for analyzing the aerodynamic performance of the front wings. This work lays the foundation for further research and development in the field of Formula 1 aerodynamics, encouraging continuous innovation and advancements in front wing design to achieve optimal performance and a competitive edge

Aerodynamic study of the wake effects on a F1 car

The present study is based on the evaluation and quantification of the aero- dynamic performance on a 2017 spec. adapted F1 car —the latest major aerodynamic update— by means of a CFD study. Both free stream and flow disturbance conditions are evaluated in order to study and quantify the effects that the wake may cause on the latter case. The CFD techniques are primarily selected as other resources —such as the us- age of a wind tunnel or any other experimental solutions—, are currently out of reach to deal with such a study. However, as the CFD discipline involves a rather strict and accurate process to be able to deal with external aerodynamic prob- lems, the methodology is accepted in order to discern whether the current F1 regulations require an urgent change in terms of aerodynamic designs

Open-Wheel Aerodynamics: Effects of Tyre Deformation and Internal Flow

Competitive performance of an F1 race car relies upon a well designed and highly developed aerodynamic system. In order to achieve this, total understanding of the downstream wake of exposed rotating wheels is essential. Components such as bargeboards and indeed much of the front wing are developed to provide pressure gradients and vortex structures to influence the wheel wake, ensuring high energy mass-flow to the sensitive leading edge of the underfloor and eventually the rear wing. Wind tunnel testing of model-scale deformable tyres has become a common occurrence in F1 in recent years although there is a significant lack of available literature, academic or otherwise, as to their use. This work has studied in detail the aerodynamic consequences which occur from the varying sidewall bulge and contact patch region making use of several techniques. These include scanning rotating tyre profiles under load, static contact patch size measurements, five-hole pressure probe wake measurements, particle image velocimetry (PIV) and load-cell drag measurements. CFD simulations utilising two industrial codes have also been performed to support the experimental work. Coordinates representing tyre profiles under a range of on-track conditions are available for other researchers to use as a basis for CFD studies. The work presented here includes a full range of representative on-track axle heights which far exceed the more conservative range usually tested in an industrial setting for longevity reasons. The most sensitive parameters for aerodynamic testing of wheels have been identified. For development of a full car, in decreasing order of priority, the following must be correctly matched to the realistic scenario: axle height, yaw condition (without glycerol - often used to reduce friction at the expense of a compromised tyre profile), camber angle, detailed internals, high inflation pressure, through-hub flow rate and least significantly the rotation of the internal brake rotor. The study of through-hub flows revealed that the external aerodynamic effect of the brake scoop inlet varies significantly with the amount of internal restriction. The pumping effect of the brake rotor was measured to be negligible compared to the restrictive effect of its internal passages and that leads to an effect known as inlet spillage with a negative cooling drag trend, whereby the drag of the wheel assembly decreases with increased through-hub flow

A CFD Study of a Multi-Element Front Wing for a Formula One Racing Car

Presently, one of the key factors in determining a success of an open wheel racecar such as Formula One or Indy car, is its aerodynamic efficiency. A modern racecar front wing can generate about 30% of the total downforce. The present study focuses on investigating the aerodynamic characteristics of such highly efficient multi-element front wing for a Formula One racecar by conducting a three-dimensional computational analysis using Reynolds Averaged Navier-Strokes model. A three-dimensional computational study is performed investigating predictive capability of the structured trimmer and unstructured polyhedral meshing model to generate a three-dimensional volume mesh for a multi-element front wing. Also, the ability of the standard k- ω Shear Stress Transport (SST) and the one equation Spalart-Allmarus turbulence models to predict the three-dimensional flow over a multi-element front wing operating in ground effect has been investigated. Furthermore, the present study also determines the effect of varying ground clearance and angle of attack. Lastly, the aerodynamic characteristics of the wing operating in the wake of racecar in front is also investigated with the help of a generic bluff body. To get more realistic results a moving ground simulation has been used. It has been observed that the RANS model is able to predict the three-dimensional flow over the double element front wing correctly. Both of the turbulence models are able to predict the flow over the front wing in decreasing ground clearance and indicate the regions of force enhancement and force reduction. However, for low ground clearances, the standard k- ω SST turbulence model is best suited as it is able to predict the flow more accurately. Moreover, the results indicate, use of unstructured polyhedral mesh model for meshing of wing is more effective. By studying the flow characteristics of the wing at different ground clearances, it has been observed that the downforce generated behaves as a function of ground clearance. Furthermore, by studying the lift and drag forces generated by the wing, it has also been observed that the wing clearly operates in three different regions which can be classified as; a region similar to free stream case, a force enhancement region and a force reduction region. In addition, by investigating the effect of increasing angle of attack for forces generated, the study indicated that for lower values of angle of attack the corresponding very low ground clearances has more impact in decreasing the downforce generated. However, for higher angle of attack, the resulting increase in camber has a significant impact than very low ride heights which leads to an increase in downforce generated. Moreover, the studies for front wing operating in wake show the downstream wing is significantly affected by the up-wash flow field from the leading racecar leading to a loss of downforce. However, the leading racecar also creates a drafting effect which can be used to get as a tow and improve straight-line speeds of following racecar

Formula SAE aerodynamic optimization

Tato práce se zabývá měřením aerodynamických charakteristik modelu závodního vozu Formula SAE v aerodynamickém tunelu, v měřítku 1:4. V první části je představen projekt Formula SAE a popsána role aerodynamiky v rámci této soutěže. Následuje přehled teoretického pozadí, které je relevantní k provedenému experimentu. Ve druhé části práce je popsán samotný experiment a prezentovány jeho výsledky. Součástí je návrh, výroba a kalibrace šestikomponentní tenzometrické váhy pro měření aerodynamického zatížení. Testy v aerodynamickém tunelu byly provedeny ve čtyřech konfiguracích, aby bylo možné určit vliv přítlačných křídel a podlahy s difuzorem na výsledné aerodynamické charakteristiky vozu.This work focuses on wind tunnel testing of a 25% scale model of a Formula SAE race car. In the first part, Formula SAE competition is introduced and role of aerodynamics within this competition is described. That is followed by review of the theoretical background that is relevant to the presented experiment. In the second part, the experiment itself is described and results presented. As part of this work, a six component strain gauge force balance was designed, manufactured, and calibrated. Wind tunnel testing was done in four different configurations to determine the influence of inverted wings and floor with diffuser on aerodynamic performance of the car.

Application of spectral/hp element methods to high-order simulation of industrial automotive geometries

Flow predictions around cars is a challenge due to massively separated flow and complex flow structures generated. These flow features are usually poorly predicted by present industrial computational fluid dynamics (CFD) codes based on a low fidelity Reynolds averaged Navier Stokes (RANS) approach simulating the mean effects of turbulence. On the other hand, high fidelity approaches resolve turbulent scales but require many more degrees of freedom than classical techniques for an accurate solution. Previous applications have shown that the coupling of the spectral/hp element method and implicit large eddy simulation (iLES) turbulence treatment could be a potential candidate to perform high-fidelity simulations. This work aims at transferring the spectral/hp element technology to the automotive industry in which high Reynolds numbers and complex geometries are typical. Recent developments in stabilisation techniques such as the discontinuous Galerkin kernel spectral vanishing viscosity (SVV) and high-order meshing capabilities open the possibility of the application of the spectral/hp element method to complex cases. The technology is first implemented to an industrial case proposed by McLaren Automotive Limited (MLA) at a realistic Reynolds number of 2,3 million based on the front wheel diameter and is compared to a RANS numerical development tool. Differences in terms of vortical structures arrangement, principally due to the front wheel wake are highlighted. In parallel, a workflow is developed to systematically address similar complex cases. The interaction between h-refinement, related to the size of the elements of the mesh, and p-refinement, corresponding to the polynomial expansion order, is investigated on the SAE notchback body. Two different hp-refinement strategies with similar numbers of degrees of freedom are employed, the first one with a fine mesh and a third-order accurate polynomial expansion and the second one with a coarse mesh and a fifth-order accurate polynomial expansion. Results show that a minimum level of h-refinement is necessary to capture flow features and that p-refinement can subsequently be used to improve their resolution. The final part focuses on wheel rotation modelling. Scale-resolving techniques are intrinsically unsteady and therefore require sophisticated techniques to correctly model rotating wheels. A procedure, built upon an immersed boundary method (IBM) called the smoothed profile method (SPM), is developed to model complex three-dimensional rotating geometries, in particular rim spokes. It is finally applied to an isolated rotating wheel case and results are compared to the moving wall (MW) and the moving reference frame (MRF) modelling techniques. It is concluded that the SPM is in better qualitative agreement with experimental results present in the literature than the two other modelling strategies.Open Acces

External Aerodynamics of Heavy Ground Vehicles: Computations and Wind Tunnel Testing

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices. Considering the latter, a thorough understanding of the airflow is a prerequisite. The present study aims to simulate the external flow field around a ground vehicle using a computational method. The model and the method are selected to be three dimensional and time-dependent. The Reynolds-averaged Navier Stokes equations are solved using a finite volume method. The Renormalization Group (RNG) k-ϵ model was elected for closure of the turbulent quantities. Initially, the aerodynamics of a generic bluff body is studied computationally and experimentally to demonstrate a number of relevant issues including the validation of the computational method. Experimental study was conducted at the Langley Full Scale Wind Tunnel using pressure probes and force measurement equipment. Experiments and computations are conducted on several geometric configurations. Results are compared in an attempt to validate the computational model for ground vehicle aerodynamics. Then, the external aerodynamics of a heavy truck is simulated using the validated computational fluid dynamics method, and the external flow is presented using computer visualization. Finally, to help the estimation of the error due to two commonly practiced engineering simplifications, a parametric study on the tires and the moving ground effect are conducted on full-scale tractor-trailer configuration. Force and pressure coefficients and velocity distribution around tractor-trailer assembly are computed for each case and the results compared with each other. Finally, this study demonstrates that it is possible to apply computational fluid dynamics for ground vehicle aerodynamics with substantial detail and fidelity. With the latest developments on computing power, computational fluid dynamics can be applied on real-life transportation problems with reasonable turn-around times, reliability, ease of accessibility and affordability. The next step is deemed to be considering such a computational methodology for analysis within an automated optimization process in improving aerodynamic designs of heavy ground vehicles