Wind Tunnel Testing

Wind tunnel testing is the traditional method for developing racing car aerodynamics. There are two distinct variants of wind tunnel testing: full scale testing with actual racing cars and reduced scale testing with purpose built models.

Panasonic Toyota F1 Car and 50% Scale Wind Tunnel Model.

Scale Model Testing.

Scale model testing has historically been the favoured method of aero development for racing cars and is likely to remain so for some time yet.  CFD is improving all the time, but is not yet a replacement for scale model wind tunnel testing. All leading F1 teams use a scale model wind tunnel program as their primary aero development tool.

Scale Model Wind Tunnel Testing has many advantages.
  • Correlation between model results and actual track performance can be excellent.  This depends on the use of a suitable wind tunnel, an accurate scale model and intelligent testing and analysis techniques.
  • Accuracy.  A top level tunnel and model should be able to measure changes to model forces of the order of 0.1% of the total forces.
  • Speed of development.  A high spec wind tunnel as used by a current F1 team will sweep through as many as 25 distinct car attitudes during a typical 15 minute run.  Each of those car attitude points will generate a full range of aero data. The data ( both measured forces and pressures ) will be available instantly and will give a very full picture of the car's aero performance throughout its operating envelope. 
  • Flexibility of testing.  Wind tunnel programs give the aerodynamicist the ability to react quickly to results and to adapt the testing program to suit.  This may be a simple 'bodged-up' change to the model, or may be the addition, or subtraction, of an entire swathe of work.  This flexibility makes the process extremely efficient.
  • Compared to full scale testing, the cost of test parts is much reduced as is the time in which they can be designed and realised.
  • Scale model testing can be cost effective (this will depend on circumstances, so click here for an explanation).
Scale Model Wind Tunnel Testing also many disadvantages.
  • A purpose built scale model will be required.  The design, manufacture and maintenance of the model will be a significant undertaking in terms of both cost and time.
  • A steady supply of accurate, high quality test components will need to be designed and manufactured to support the program.
  • Experienced model technicians will be required to prepare the model and the test components and to operate the model during a wind tunnel test.
  • Mechanical failures.  Wind tunnels and scale models are complex devices and gremlins can strike.  A well run program will minimise the impact of these problems, but they can never be entirely eliminated.
  • Information.  A wind tunnel should produce accurate results for both the forces acting on the model and the static pressures acting on it's surfaces.  Whilst this data is the most important to the aerodynamicist, it cannot compete with the range aero data and derivatives calculable from a CFD run.
  • Repeatablity.  A well designed model and tunnel will limit any problems with data repeatability, but wind tunnel tests without some time spent chasing and diagnosing these problems will be few and far between.
  • Scale model testing can expensive (this will depend on circumstances, so click here for an explanation).

Full Scale Vehicle Wind Tunnel Testing.

Full scale vehicle testing usually involves running an actual racing car in a wind tunnel.  In some respects, this can be very cheap as a racing team will usually have access to a suitable test car with minimal additional resource being required.  It can also be very expensive however, as test component production will be much more complex and expensive and the cost of hiring or running a suitable wind tunnel will also be very large.  Full scale wind tunnel tests are particularly useful for investigating the following phenomena, amongst others.
    • Flow instablility issues. The accurate modelling of track Reynolds numbers can be achieved, and hence real world track condition can be mimicked.
    • Aeroelastic effects. Aeroelasticity relates to the interaction of the aerodynamic forces acting on a surface and resulting deformations of its structure.  Cunning manipulation of these effects can produce significant reductions in lap time. Only a full scale test can accurately model both aerodynamic and structural effects simultaneously.
    • Detailling of small components.  Fine detailing of aero sensitive areas of the car can produce substantial gains in performance. A full scale test facility allows the aerodynamicist the best opportunity to fine-tune geometry without the worry of scale effects.

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