Experimental Techniques for the Aerodynamic Development of Convertible Cars 920347

The aerodynamic development of a convertible passenger car requires the optimization of additional characteristics, when compared to those which are considered for normal passenger cars.
To be more specific, this means that, in addition to the usual requirements of hard-top passenger cars, (i.e. low values of the aerodynamic coefficients Cd, Cl, Cmy, etc., optimization of the cooling flow and achievement of low aerodynamic noise), it is important to also check the following:
  • that the car with the soft top in the closed position, shows:
    • reduced soft-top ballooning
    • an acceptable increase in interior noise relative to a hard top
    • aerodynamic coefficient values which are not too different when compared with the hard-top version
  • that the car in the open configuration (soft top down) shows:
    • an acceptable increase of the aerodynamic coefficients when compared with the hard-top version, with side windows both raised and lowered
    • a good comfort level inside the passenger compartment, i.e., air flow velocities close to zero near the passengers' heads.
To achieve this,in some cases,it has been necessary to set up new instrumentation for these measurements, i.e., such as for measurement of soft-top ballooning.
In other cases, the standard techniques (flow mapping with the 14-hole probe, acoustic dummies, etc.) are used, although in a different way than for the development of normal passenger cars.
This paper describes these techniques and the way they are employed for the aerodynamic development of convertible cars.


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