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Condition Simulation in Vehicle Aerodynamics Computation
Čavoj, Ondřej ; Sloupenský, Zdeněk (referee) ; Popela, Robert (referee) ; Píštěk, Václav (advisor)
Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.
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Condition Simulation in Vehicle Aerodynamics Computation
Čavoj, Ondřej ; Sloupenský, Zdeněk (referee) ; Popela, Robert (referee) ; Píštěk, Václav (advisor)
Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.
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