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Aerodynamic Optimization of Vehicle Configuration Based on Adjoint Method

ANSYS Inc.-Tushar Jadhav
SAIC Volkswagen Automotive Co., Ltd.-Chao Ren, Hua Zhou, Haibo Wu, Qian Chen
  • Technical Paper
  • 2020-01-0915
To be published on 2020-04-14 by SAE International in United States
Due to the increasingly stringent environmental regulations all around the world confronted by exhaust emission and energy consumption, improving fuel economy has been the top priority for most automotive manufacturers. In this context, the basic process for vehicle shape development has evolved into optimizing the design to achieve better aerodynamic characteristics, especially drag reduction. Of all the optimization approaches, the gradient-based adjoint method has currently received extensive attention for its high efficiency in calculating the objective sensitivity with respect to geometry parameters, which is the first and foremost step for subsequent shape modification.In this work, the main goal is to explore the adjoint method through optimizing the vehicle shape for a lower drag based on a production SUV. Firstly, the influence of different mesh schemes was discussed on sensitivity prediction of aerodynamic drag. Secondly, according to the sensitivity distribution, several key areas, like the side mirrors, A pillars, air dam, and rear lamps, were respectively altered through mesh morphing process. Furthermore, the optimized effect was validated by steady as well as transient simulation. Steady Reynolds…
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Fluid-Structure Interaction of a Spring-Mounted Symmetrical Rigid Wing for Drag Reduction of Cars at Higher Wind Velocities

Kingston University-George Haritos
University of Duisburg-Essen-Simon Fels
  • Technical Paper
  • 2020-01-5037
Published 2020-03-10 by SAE International in United States
This paper details an aeroelastic concept for an adaptive and passive wing, which is primarily aimed for use within the automotive sector to reduce drag and fuel emissions. The work will also be of interest in the motorsport sector to improve performance and also some applications within the aerospace and renewable energy sectors. The wind tunnel testing of a spring-mounted symmetrical NACA 0012 wing in freestream is studied over 0° to 40° angles of incidence. General operation of the concept is verified at low angles in the pre-stall region with that of a theoretical estimation using finite and infinite wings. Three distinct regions are identified, pre-stall, near-stall, and post-stall. The transient limitations associated in the near-stall region with variations in spring loading and flow velocities are discovered. It is identified as a periodic self-sustained oscillation with nondimensional reduced frequencies in the range from 0.14 to 0.22. Furthermore, performance in the post-stall region along with pre-stall is reported, and methods for the adjustment of the elastic element for a desired response are introduced. Evaluation is conducted…
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Design of Light Weight Spoiler for Efficient Aerodynamic Performance of a Vehicle

Mahindra & Mahindra, Ltd.-Praveen Kumar, Aditya Pandey, Vivek KV Shenoy, BalaChandar R, Ayan Chakraborty
Published 2019-10-11 by SAE International in United States
The spoiler is functional as well as aesthetic part fitted on the vehicles to improve the vehicle aerodynamic performance and better aesthetic appeal. The improvement of aerodynamics performance of the vehicle at higher speeds is achieved by reducing the overall vehicle coefficient of drag. This helps in better handling and improved fuel efficiency of the vehicle thus contributing to development of greener vehicle.In this project, our main focus is to reduce overall vehicle coefficient of drag, Design a light weight spoiler and improve the vehicle aesthetic appearance.
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Study for Manufacturing a Cost Effective, Light Weight, Single Piece Injection Molded Spoiler

Maruti Suzuki India Ltd.-Tarun Gupta, Nilesh Rathod
Published 2019-01-09 by SAE International in United States
Today automotive sector has become very dynamic. There is renewed emphasis on safety through adoption of new regulations, electric vehicles are on the verge of replacing ever evolving engine technology, emission norms are getting stringent year by year & several companies are trying to make vehicles more efficient by adoption of new light weight or high strength materials and altering manufacturing methods.In one of the new vehicle programs, there was focus on vehicle styling. In order to improve the styling, back door spoiler was to be considered from design stage itself.Back door spoiler is added in high speed vehicles for creating a downward force to improve the vehicle hold on road. However, nowadays in passenger vehicles that purpose has been subsided and spoiler is given in automotive vehicles for aesthetics or giving vehicle a sporty appearance. For instance in our case it was given to augment aesthetics.This would have resulted in additional cost and weight. Hence, challenge was to introduce it in minimal cost and weight and still it should pass all performance criteria.Each and…
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Development and Prediction of Vehicle Drag Coefficient Using OpenFoam CFD Tool

Tata Motors, Ltd.-Kundan Biswas, Ganesh Gadekar, Sujit Chalipat
Published 2019-01-09 by SAE International in United States
Vehicle aerodynamic design has a critical impact on fuel efficiency of the vehicle. Reducing aerodynamic wind resistance of the vehicle's exterior shape and reducing losses associated with requirements for engine compartment cooling through vehicle front openings plays key role in achieving desired aerodynamic efficiency.Today fairly large number of computational fluid dynamics (CFD) simulations are being performed during the vehicle aerodynamic design and development process and it is rapidly increasing day by day. Vehicle aerodynamic design and development process involves mainly aerodynamic shape development, aerodynamic optimizations of vehicle external components (side view mirror, spoilers, underbody shield etc.) and number of” what if studies during preliminary design process.Licensing costs of the available commercial CFD simulation solver has significant impact on product development cost when numbers of aerodynamic simulations expand. To address this aspects, open source code “OpenFoam” CFD have become popular in the aerodynamic community.This papers summarizes CFD simulation results for three standard MIRA body configurations (Notchback, Fastback and Estate back) using OpenFoam solver. In this study, steady state simulations with Realizable K-epsilon turbulence models were performed…
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Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Levon Larson, Sudesh Woodiga
  • Journal Article
  • 2018-01-0740
Published 2018-04-03 by SAE International in United States
The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body. This airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag; this component of cooling drag is known as cooling interference drag. One mechanism that has been commonly utilized to directly influence the cooling drag, by reducing the engine airflow, is active grille shutters (AGS). For certain driving conditions, the AGS system can restrict airflow from passing through the heat exchangers, which significantly reduces cooling drag. The difference in drag between the AGS vanes being open and closed is referred to as AGS drag. Another vehicle component that influences the cooling drag is chin spoilers. Chin…
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Aerodynamics Development for a New EV Hatchback Considering Crosswind Sensitivity

Nissan Motor Co., Ltd.-Yusuke Iinuma, Keiichi Taniguchi, Munehiko Oshima
Published 2018-04-03 by SAE International in United States
An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model. A wind tunnel with a 0 degree yaw angle is generally used in new vehicle development, but this condition is different from the real world with a small yaw angle due to natural crosswinds. The new EV…
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On the Aerodynamics of an Enclosed-Wheel Racing Car: An Assessment and Proposal of Add-On Devices for a Fourth, High-Performance Configuration of the DrivAer Model

Cranfield University-Renan Francisco Soares, Andrew Knowles, Sergio Goñalons Olives, Kevin Garry, Jennifer Holt
Published 2018-04-03 by SAE International in United States
A modern benchmark for passenger cars - DrivAer model - has provided significant contributions to aerodynamics-related topics in automotive engineering, where three categories of passenger cars have been successfully represented. However, a reference model for high-performance car configurations has not been considered appropriately yet. Technical knowledge in motorsport is also restricted due to competitiveness in performance, reputation and commercial gains. The consequence is a shortage of open-access material to be used as technical references for either motorsport community or academic research purposes.In this paper, a parametric assessment of race car aerodynamic devices are presented into four groups of studies. These are: (i) forebody strakes (dive planes), (ii) front bumper splitter, (iii) rear-end spoiler, and (iv) underbody diffuser. The simplified design of these add-ons focuses on the main parameters (such as length, position, or incidence), leading to easier manufacturing for experiments and implementation in computational studies. Consequently, a proposed model aims to address enclosed-wheel racing car categories, adapting a simplified, 35% scaled-model DrivAer Fastback shape (i.e. smooth underbody, no wheels, and with side mirrors).Experimental data were obtained…
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New Reference PMHS Tests to Assess Whole-Body Pedestrian Impact Using a Simplified Generic Vehicle Front-End

Eric Song, Philippe Petit, Jerome Uriot, Pascal Potier
CEESAR-Denis Dubois
Published 2017-11-13 by The Stapp Association in United States
This study aims to provide a set of reference post-mortem human subject tests which can be used, with easily reproducible test conditions, for developing and/or validating pedestrian dummies and computational human body models against a road vehicle. An adjustable generic buck was first developed to represent vehicle front-ends. It was composed of four components: two steel cylindrical tubes screwed on rigid supports in V-form represent the bumper and spoiler respectively, a quarter of a steel cylindrical tube represents the bonnet leading edge, and a steel plate represents the bonnet. These components were positioned differently to represent three types of vehicle profile: a sedan, a SUV and a van. Eleven post-mortem human subjects were then impacted laterally in a mid-gait stance by the bucks at 40 km/h: three tests with the sedan, five with the SUV, and three with the van. Kinematics of the subjects were recorded via high speed videos, impact forces between the subjects and the bucks were measured via load cells behind each tube, femur and tibia deformation and fractures were monitored via…
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Structural Concept of an Adaptive Shock Control Bump Spoiler

DLR German Aerospace Center-Markus Kintscher, Hans Peter Monner
Published 2017-09-19 by SAE International in United States
Drag reduction technologies in aircraft design are the key enabler for reducing emissions and for sustainable growth of commercial aviation. Laminar wing technologies promise a significant benefit by drag reduction and are therefore under investigation in various European projects. However, of the established moveable concepts and high-lift systems, thus far most do not cope with the requirements for natural laminar flow wings. To this aim new leading edge high-lift systems have been the focus of research activities in the last five years. Such leading edge devices investigated in projects include a laminar flow-compatible Kruger flap [1] and the Droop Nose concept [2, 3] and these can be considered as alternatives to the conventional slat. Hybrid laminar flow concepts are also under investigation at several research institutes in Europe [4]. Another challenge associated with laminar wings aside from the development of leading edge moveables is the need to address the control of aerodynamic shocks and buffeting as laminar wings are sensitive to high flow speeds. One possible method of decreasing the wave drag caused by the…
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