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On the Influence of Underhood Flow on External Aerodynamics of the DrivAer Model


The interaction of underhood flow with external aerodynamics is part of the main topics for the development of automotive aerodynamics. In particular, the location and design of cooling air exits as well as the mass flow through the radiator package are considered to be important factors. The DrivAer is an open-source, aerodynamic reference model, which has a realistic overall geometry compared to rather simple, generic shapes such as the SAE body. The model is flexible in use as it provides different rear end and wheel designs. The open-grille upgrade of the DrivAer enhances the potential of the body towards a reference model for more detailed, open cooling investigations.

In the present study, the 40% scale Mock-Up DrivAer model of the Technical University of Munich was upgraded with underhood flow for wind tunnel tests with moving ground simulation. The wind tunnel measurements covered different underhood flow configurations including variations for the pressure drop of the radiator package and different locations for cooling air exits – both for different rear end shapes of the model. Additionally, the effect of underhood flow on the aerodynamics of both the notchback and the estateback rear end were calculated for six different radiator packages using DDES simulations with OpenFOAM®.

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Delayed Detached-Eddy Simulation


Detached-Eddy Simulation


Large Eddy Simulation


Reynolds Averaged Navier-Stokes Equations


Spalart-Allmaras turbulence model


Technical University of Munich


Wind Tunnel A (Large Wind Tunnel TUM)

\( A_{c} \) :

Closed area of the perforated sheets

\( A_{o} \) :

Open/exposed area of the perforated sheets

\( A_{o} /A_{c} \) :

Openness ratio of the perforated sheets

\( C_{D} \) :

Drag coefficient

\( C_{L,f} \) :

Front lift coefficient

\( C_{L,r} \) :

Rear lift coefficient

\( \Delta C_{D,c} \) :

Effect of underhood flow on drag coefficient \( C_{D} \)

\( \Delta C_{L,f,c} \) :

Effect of underhood flow on front lift coefficient \( C_{L,f} \)

\( \Delta C_{{L,{\text{r}},c}} \) :

Effect of underhood flow on rear lift coefficient \( C_{L,r} \)


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Collin, C., Müller, J., Islam, M., Indinger, T. (2018). On the Influence of Underhood Flow on External Aerodynamics of the DrivAer Model. In: Wiedemann, J. (eds) Progress in Vehicle Aerodynamics and Thermal Management. FKFS 2017. Springer, Cham.

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