Development of A Generic SUV Model for Aerodynamic

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

04.12.2019Universität Stuttgart 2

Overview

• Motivation

• Some Existing Generic Models

• Development of the AeroSUV

• Results

• Results of the AeroSUV

• Comparison to the DrivAer

• Summary


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


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


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



Requirements

• The resulting range of geometric dimensions



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



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



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



Geometry of the AeroSUV

• Rear end variations

The three DrivAer rear ends can be mounted on the AeroSUV body



Details of the IVK/FKFS AeroSUV Model

• Underbody

Underbody geometry Wheel geometry with replaceblerim cover



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


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


Results

Experimental Results of the AeroSUV

• AeroSUV baseline (standard ride height and open cooling)


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


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


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


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


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


Results


• Drag development along x-direction based on CFD

Main difference occurs at the vehicle front and wake


Results


• 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


Results


• 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


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/)

E-Mail

Telefon +49 (0) 711 685-

Fax +49 (0) 711 685-

Universität Stuttgart

Thank you!

Chenyi Zhang

65613

60401


Kraftfahrwesen

[email protected]

Pfaffenwaldring 12, 70569 Stuttgart, Germany


Kraftfahrwesen

Documents

Development of A Generic SUV Model for Aerodynamic