development of a generic suv model for aerodynamic
TRANSCRIPT
Institut für Verbrennungsmotoren und
Kraftfahrwesen
Chenyi Zhang, Max Tanneberger, IVK Universität Stuttgart
Timo Kuthada, Felix Wittmeier, Jochen Wiedemann, FKFS
3DEXPERIENCE Conference Germany
21.11.2019
Development of A Generic SUV
Model for Aerodynamic Research –
the AeroSUV
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Overview
• Motivation
• Some Existing Generic Models
• Development of the AeroSUV
• Results
• Results of the AeroSUV
• Comparison to the DrivAer
• Summary
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Motivation
• Since the introduction of WLTP, the effect of aerodynamics on the determined
consumption has increased
• Within the last years, SUVs obtain a strong increasing share in the global market
• There is a lack of detailed generic SUV models for aerodynamic research
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Some Existing Generic Models
SAE reference geometry(SAE Standard J2071, 1994)
Generic SUV (Al-Garni et al. 2004)
Generic SUV (Wood et al. 2014)
DrivAer model(Heft et al. 2012)
Generic SUV with realistic details(Today)
Mira reference model(Carr et al. 1986)
It is necessary to develop a generic SUV model with realistic geometry details for
aerodynamic research
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Development of the AeroSUV
Requirements
• Legal guidelines for the geometric restrictions
– Off-road vehicle category defined by the European Community (M1G)
– Code of Federal Regulations (CFR) §523.5-b in the USA
• Overall dimensions
– Derived from actual mid-class SUVs in the market
• Adjustability
– Adjustable ride heights
– Modularity and applicability to the DrivAer rear ends
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Development of the AeroSUV
Requirements
• The resulting range of geometric dimensions
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Development of the AeroSUV
Aerodynamic Development
• Target cD value: 0.30 – 0.35
• 25 % model-scale
• Numerical method
Tool: PowerFLOW
– Simplified simulation volume with a blockage ratio of 0.1 %
– 78 Million fluid cells with a finest cell size of 0.6 mm
– Cooler module simulation with porous media
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Development of the AeroSUV
Aerodynamic Improvement
• Investigated geometric parameters
Air Duct for the
Cooling Flow
Rear Underbody
Panel
Top-View Side-View
CFD-simulation gives a good prediction in the aerodynamic development process
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Development of the AeroSUV
Geometry of the AeroSUV
• Overall dimensions of the optimized AeroSUV in full-scale (baseline)
The ride height is adjustable in a range of delta -50 to +50 mm relative to the baseline
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Development of the AeroSUV
Geometry of the AeroSUV
• Rear end variations
The three DrivAer rear ends can be mounted on the AeroSUV body
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Development of the AeroSUV
Details of the IVK/FKFS AeroSUV Model
• Underbody
Underbody geometry Wheel geometry with replaceblerim cover
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Development of the AeroSUV
Details of the IVK/FKFS AeroSUV Model
• Front-end
Cooling system and engine bay geometry Pressure loss over flow speed for the AeroSUV radiator simulator
1600
Δp
in P
a
800
400
0
1200
v in m/s0 2 6 84 10 12 1614
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Results
Experimental Setup
• Model scale wind tunnel of University of Stuttgart (MWK)
– Model scale: 25 %
– Goettingen-type wind tunnel
– Nozzle size: 1.65 m2
– Max. test speed: 80 m/s
– 5-belt road simulation system
The AeroSUV in the test section of the MWK
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Results
Experimental Results of the AeroSUV
• AeroSUV baseline (standard ride height and open cooling)
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Results
Experimental Results of the AeroSUV
• Influence of the cooling air
-0.03 -0.02 0.00 0.01-0.01 0.02 0.03
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Results
Comparison between Experiments and Numerical Simulations
• Total pressure distribution of the 25 % AeroSUV estate back baseline
(25 mm downstream of the vehicle base)
Similar contour for experiment and simulation can be observed
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Results
Numerical Results of the Cooling Air Flow
• Velocity distribution on a z-aligned plane in the engine compartment of the AeroSUV
estate back baseline
60 % of the cooling air flow exits the engine compartment through wheel houses
U/U∞
0
1.3
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Results
Comparison between AeroSUV and DrivAer Baseline
• Geometric difference
– Overall dimensions
– Front end
The air intake area of AeroSUV is extended by 58 % compared to DrivAer
The cross sectional area of AeroSUV is increased by 14 % compared to DrivAer
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Results
Comparison of the Flow Characteristics between AeroSUV and DrivAer
• Behavior to cross-wind measured in MWK (reference β = 0°)
The results show symmetrical reaction of the cD value of the AeroSUV to both positive and
negative yaw angles
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Results
Comparison of the Flow Characteristics between AeroSUV and DrivAer
• Drag development along x-direction based on CFD
Main difference occurs at the vehicle front and wake
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Results
Comparison of the Flow Characteristics between AeroSUV and DrivAer
• Iso-surface for the total pressure of cpt = 0 based on CFD
Different pressure loss in the wake of the front wheel can be observed
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Results
Comparison of the Flow Characteristics between AeroSUV and DrivAer
• Total pressure distribution based on CFD in an x-aligned slice 25 mm downstream of
the base (25 % model scale)
Different wake can be observed
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Summary
• A new generic SUV – the AeroSUV – has been designed
• Layout and design are according to the European and American guidelines for this
vehicle class
• First experimental and numerical results of the 25 % AeroSUV model were presented
• The geometry represent a typical SUV with an optimization for the aerodynamic
properties
• The first experimental wind tunnel test and numerical simulations are in good
accordance and confirm the targeted aerodynamic coefficients
• Comparative investigations between the AeroSUV and the DrivAer were carried out:
obvious difference can be observed at the vehicle front and wake
• The geometric data of the AeroSUV will be published on the European Car
Aerodynamic Research Association website (http://www.ecara.org/)
Telefon +49 (0) 711 685-
Fax +49 (0) 711 685-
Universität Stuttgart
Thank you!
Chenyi Zhang
65613
60401
Institut für Verbrennungsmotoren und
Kraftfahrwesen
Pfaffenwaldring 12, 70569 Stuttgart, Germany
Institut für Verbrennungsmotoren und
Kraftfahrwesen