Research Papers: Flows in Complex Systems

Experimental and Numerical Aerodynamic Analysis of a Passenger Car: Influence of the Blockage Ratio on Drag Coefficient

[+] Author and Article Information
Armagan Altinisik

TOFAS—FIAT (Turkish Automotive
Factory Incorporated Company),
Yeni Yalova Yolu Cad. No: 574,
Bursa 16369, Turkey
e-mail: armagan.altinisik@tofas.com.tr

Emre Kutukceken

Kemalpaşa Mahallesi Şehit Yüzbaşı
Adem Kutlu Sokak No: 21 Elmadağ,
Ankara 06780, Turkey

Habib Umur

Mechanical Engineering Department,
Faculty of Engineering and Architecture,
Uludag University,
Gorukle Campus,
Bursa 16059, Turkey

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received June 5, 2014; final manuscript received March 22, 2015; published online April 29, 2015. Assoc. Editor: Francine Battaglia.

J. Fluids Eng 137(8), 081104 (Aug 01, 2015) (14 pages) Paper No: FE-14-1288; doi: 10.1115/1.4030183 History: Received June 05, 2014; Revised March 22, 2015; Online April 29, 2015

Experimental and numerical investigations were performed to determine the pressure distributions and the drag forces on a passenger car model. Experiments were carried out with 1/5th scale model FIAT Linea for 20% and ~ 1% blockage ratios in the Uludag University Wind Tunnel (UURT) and in the Ankara Wind Tunnel (ART), respectively. Computational fluid dynamics (CFD) analysis for 1/5th scale model with 0%, 5%, and 20% blockage ratios was performed to validate various blockage correction methods supplementary to the experimental results. Three-dimensional, incompressible, and steady governing equations were solved by STAR-CCM+ code with realizable k–ε two-layer turbulence model. The calculated drag coefficients were in good agreement with the experimental results within 6%. Pressure coefficients on the model surfaces have shown similar trends in the experimental and numerical studies. Some of the existing blockage correction methods were successfully compared in this study and predicted drag coefficients were within ± 5%. The authors propose the continuity and the Sykes blockage correction methods for passenger car models because they are very simple and practical and they can be used economically for engineering applications.

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Fig. 1

(a) Dimensions of 1/5th scale model (in mm) and (b) Positions and quantities of the pressure holes

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Fig. 2

Scaled view of 1/5th scale model in UURT/ART wind tunnels

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Fig. 3

The y+ distributions on the model wall surfaces (this study)

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Fig. 4

Section of domains for various blockage ratios and sample midsection of the computational domain

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Fig. 5

Flow patterns: (a) 1/5th model tuft test at UURT (30 m/s) and (b) CFD skin friction distribution

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Fig. 6

(a) Velocity profiles on the model at 30 m/s, (b) comparison of the velocity profiles at 3 m/s and 30 m/s, and (c) comparison of the experimental and CFD velocity profiles

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Fig. 7

Comparison of the boundary layer velocity profiles: (a) with the study of Koike et al. [4] and (b) with the study of Jenkins [68]

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Fig. 8

(a) Streamwise wake velocity profiles at 3 and 30 m/s and (b) comparison of the CFD and the experimental velocity profiles in rear wake

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Fig. 9

Comparison of Cp distributions on model surfaces at different blockage ratios

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Fig. 10

Comparison of the CFD Cp distributions with UURT and ART experimental results

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Fig. 11

Comparison of centerline pressure distribution at rear part of the models with the study of (b) Akasaka and Ono [57] and (a) present study

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Fig. 12

CFD surface pressure contours and distributions with increasing blockage effect

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Fig. 13

Comparison of 1/5th scale FIAT Linea centerline Cp distributions with various models in the literature




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