Zitong's Portfolio and Digest

Lap time simulation has long been used to simulate race-car performance on a given circuit. It is useful for determining the optimal set-up for a given circuit; it can also be used to balance different design parameters during the concept design stage. However, most lap-time simulations use single-value lift and drag coefficient to model the aerodynamic performance of a race car. It is not difficult to realize that the aerodynamic performance of a race-car depends on many things, such as the yaw angle and ride-height. In my undergraduate final-year project, I studied the variations of lift coefficient with respect to the yaw angle and ride heights. In the second semester of my graduate study, I was finally able to develop a lap-time simulation code with MATLAB that also incorporates these data. There are a few findings from this project: (1) The lap-time variation due to the aerodynamic performance variation is not negligible; (2) Aerodynamic performance maps ...

This project aims to analyze a simplified space-frame chassis of a Formula SAE racecar. The finite element analysis will look at the maximum stress and displacement of the chassis with the mounted engine load and suspension pickup. Matlab and Abaqus were both used for the FEM solutions and the results from the two were compared. Results were very similar for displacement but some differences exist for the stress values as different ways of intepretations are used. I. Introduction Space frame chassis are commonly used in race cars. The goal of race car chassis is to be lightweight and rigid. As a space frame chassis utilizes a tubular design, it is convenient for prototyping and the suspension, engine, and body panels are directly attached to the chassis. The space frame is an idealized model of the structure built from rigid linked connected to freely rotating nodes and it tries to achieve a perfectly rigid frame.  This project analyzes the maximum stress and displacem...

This blog is mainly a summary of what has been done to understand and possibly predict the aerodynamic performance of road cars on road. While it might sound a bit repetitive to say "road cars on road", the fact is a lot of aerodynamic study of road cars are done in a rather calm wind tunnel. That could result in some significant difference from real-world on-road conditions. If only the straight-line drag coefficient is used to predict a car's fuel consumption over a certain cycle, chances are it will be underestimated. To address this, the concept of "wind-averaged drag" is brought forward. First of all, for a given ambient wind condition, the resultant velocity and aerodynamic yaw angle can be calculated using the equations below: V_res = { [V_car + V_wind * cos(theta)]^2 + [V_wind * sin(theta)]^2 )^0.5 Ψ = atan{ [V_wind * sin(theta)] / [V_car + V_wind * cos(theta)] } Wind Speed (V_w), Vehicle Speed (V_v) and Resultant Speed (V_RES) courtesy of ...

This blog mainly discusses some interesting observations about the mathematical models for an airfoil (aerofoil) and a tire (tyre). My professor stressed that the essential external forces applied to an automobile only include aerodynamic ones and ones through the tires. And I find it quite interesting that some forces acting upon an airfoild and a tire can all be expressed in the form of: F = ka + C For an airfoil, F can be seen as the lift and k the lift coefficient.  a in this case would be the angle of attack (AOA). C  is the result of an airfoil's camber. For a tire,  F   can be seen as the lateral force,  k  the cornering stiffness and  a   the slip angle. C is due to the tire's camber and is known as the "camber thrust". It is also noticed that this linear expression only holds true for a limited range of  a , which is nevertheless where an airfoil or a tire normally opereates. The following two graphs would be helpf...