Aero Development Challenges

The aerodynamic design and development of racing cars is a particularly difficult task to undertake. Technical publications frequently refer to it as a 'black art'.  Experience is everything.  The technical solutions and techniques developed to tackle the problems are complex and difficult to master.  
 
So, why is the aero design of racing cars so difficult?  There are two basic reasons:
  • Technical Regulations.  Racing cars have to be designed within the technical regulations of the racing series in which they compete.  These technical regulations are written by governing bodies to constrain car performance to maintain an acceptable level of driver and spectator safety. By way of example, these are the FIA Formula 1 technical regulations. The racing car aerodynamicist is not only pitted against the laws of fluid mechanics, but also those of the technical regulations.  The aerodynamicist has to persuade the airflow to perform against a multitude of artificial constraints.
    • The aerodynamicist does not have a free hand with the design of the car geometry. 
    • Aerofoils may be limited to small volumes and areas of the car. 
    • Certain surfaces may be limited to prescribed shapes. 
    • Maximum and minimum dimensions may be imposed on the designer. 
    • Undesirable shapes like drivers heads and road wheels might be stuck out into the airflow.  
  • Environment.  Racing cars exist in an aerodynamically challenging environment.
    • Typically, the cars operate with very low ground clearance, to the extent that most are fitted with skids to allow the cars to skim the ground at high speeds. 
    • Aerofoils and surfaces work in close proximity to each other giving rise to significant interactions between different parts of the car. As a result it is not possible to effectively design individual parts of the car in isolation, rather, the entire car must be designed simultaneously. 
    • Air flows are highly three-dimensional, with high levels and variations of vorticity. 
    • The cars frequently feature bluff bodies (open wheels on F1 and Indycars for example).  These generate large, unsteady wakes which impinge on, and interact with, other parts of the cars.  
    • Aerofoils and surfaces are frequently operated close to, or beyond, the point where the airflow starts to separate from the surfaces and often feature large adverse pressure gradients.  This is necessary to obtain optimum performance, but risks flow instability and stall.  
    • The car generates a huge amount of heat from the brake and engine systems.  The aerodynamicist must manage multiple cooling flows to maintain temperatures within acceptable limits.  
    • The cars do not maintain a fixed attitude, so the aerodynamicist must ensure that the performance characteristics remain within acceptable limits throughout the car's operating envelope.  For instance, the car's front and rear ride heights, front wheel steering angle, car yaw, car roll and tyre deflection will all vary significantly around a lap.