| dc.description.abstract | Every year, the student organization ION racing design and manufacture a race car that is to compete in the international competition Formula Student. The car is designed from scratch yearly and is a combined effort of bachelor and master students, specializing in different disciplines at the University of Stavanger. The competition is held at Silverstone UK in July, every year.
The objective of this thesis is to obtain necessary skills and experience in application of aerodynamic analysis in design of this student produced race car. The competition has a set of design limitations and specifications that needs to be met for the car to compete. The scope of the bachelor thesis is evaluating the performance of the previous rear-wing of the car and developing new concepts that can improve its performance, while meeting the design requirements set by the competition. Improving the aerodynamics is important and could be what grants the edge at Silverstone.
The evaluation was done by comparing Computational fluid dynamics simulations with experimental data obtained through wind tunnel testing and with visual inspection techniques. This helps verify the flow behaviour of the simulations and inspect the similarities or differences. The simulations of the previous rear wing showed that an unwanted vortex on the outer side of the end plate generated a low pressure area, that contributes with additional drag to the system. To reduce the effect of this vortex and maintain the down force, two design concepts were developed, one cutout design and one slit design.
Size capacity for the experimental tests are limited by the area of the wind tunnel test section. The test section is too small to test real scale models and therefore the concept rear wings were scaled down 3.5 times. In addition, the width of the rear wing was decreased by reducing the width of the airfoils to reduce the significance of blockage effects. End-plates were cast in carbon fiber with resin and an aluminium sandwich structure to provide extra stiffness. The surface finish was improved by sanding and polishing them by hand.
Comparing the models, simulations of the force distribution on the profiles indicate that the drag force is the lowest on the base profile, with the highest down-force. Compared to the base model, the experimental tests in the wind tunnel show that the cutout design is able to generate less drag and a higher down force, while the slit concept generates less drag but at the cost of a lower down force.
The experimental data confirms the general behaviour of the airflow obtained from the simulations. The significance of the design features however, seem underestimated. The drag reduction achieved by the concepts seem negligible in simulation. The experimental results indicate that the cutout design is the best performing concept. When dividing the respective drag and lift coefficients obtained from simulations, with the coefficients calculated from the wind tunnel data, we obtain a constant ratio in the interval (1.56 +- 0.13)
This provides a bridge that unites the experimental data with the simulations. The concepts prove to have potential, but needs to be further developed to reach a satisfactory level. The data obtained is not sufficient for a conclusion. | |
