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Technical Paper

Wind Noise and Drag Optimization Test Method for Sail-Mounted Exterior Mirrors

2003-05-05
2003-01-1702
An L18 Taguchi-style Design of Experiments (DOE) with eight factors was used to optimize exterior mirrors for wind noise and drag. Eighteen mirror properties were constructed and tested on a full size greenhouse buck at the Lockheed low-speed wind tunnel in Marietta, GA. Buck interior sound data and drag measurements were taken at 80 MPH wind speed (0° yaw angle). Key wind noise parameters were the fore/aft length of mirror housing and the plan view angle of the mirror housing's inboard surface. Key drag parameters were the fore/aft length of the mirror housing, the cross-section shape of the mirror pedestal, and the angle of the pedestal (relative to the wind).
Technical Paper

Wake Structures of Rectangular Bodies with Radiused Edges Near a Plane Surface

1999-03-01
1999-01-0648
Almost all published results of wake measurements for ground vehicles or similar shapes have included very limited information on streamwise development of wake structures. This is typically a result of the fact that the wake measurements have been conducted as parts of particular vehicle development efforts. So the focus has been on the incremental changes in the wakes associated with alternative geometries or buildup of various parts. The objectives are typically reached by limiting the surveys to a single streamwise plane. The present study, by contrast, is a study of wake development for a series of relatively simple rectangular shapes with radiused edges with a systematic variation in the ratio of height to width or “Aspect Ratio”.
Technical Paper

Validation of SEA Wind Noise Model for a Design Change

2003-05-05
2003-01-1552
A wind noise model of a vehicle has been developed using Statistical Energy Analysis (SEA) with measured turbulent pressure data as the source input. Empirical formulas are used to scale the input data for changes in flow and design parameters. Wind tunnel tests have been conducted on a standard and modified vehicle to validate the SEA model and the input scaling. The results show good correlation with both the exterior turbulent pressure levels and the interior sound pressure levels across the audio frequency range.
Technical Paper

Use of Raman Spectroscopy to Identify Automotive Polymers in Recycling Operations

2000-03-06
2000-01-0739
To support its recycling efforts, Ford Motor Company is using a Raman based instrument, the RP-1, co-developed with SpectraCode Inc. to identify unknown polymeric parts. Our recycling initiative involves detailed dismantling of our vehicles into individual parts, calculating the percentage recyclability and making recommendations for the future use of recycled polymers. While Ford has voluntarily adopted the SAE J1344 marking protocol for identifying part material composition, a large number of unmarked parts still exist and require identification. This identification is being done with the help of RP-1. To facilitate this identification, we have generated an accurate reference library of Raman spectra for comparison to those of unknown materials. This paper will describe the techniques that were used to develop and refine the RP-1 reference library to identify automotive polymers, especially black/dark plastics.
Technical Paper

Update on the Developments of the SAE J2334 Laboratory Cyclic Corrosion Test

2003-03-03
2003-01-1234
The Corrosion Task Force of the Automotive/Steel Partnership has developed the SAE J2334 cyclic laboratory test for evaluating the cosmetic corrosion resistance of auto body steel sheet. [Ref. 1] Since the publishing of this test in 1997, further work has improved the precision of J2334. In this paper, the results of this work along with the revisions to the J2334 test will be discussed.
Technical Paper

Uncertainty Analysis of Aerodynamic Coefficients in an Automotive Wind Tunnel

2005-04-11
2005-01-0870
This paper presents an uncertainty analysis of aerodynamic force and moment coefficients for production vehicles in an automotive wind tunnel. The analysis uses a Monte Carlo numerical simulation technique. Emphasis is placed on defining the elemental random and systematic uncertainties from the tunnel’s instrumentation, understanding how they propagate through the data reduction equations and under what conditions specific elemental error sources are or are not important, and how the approach to data reduction influences the overall uncertainties in the coefficients. The results of the analysis are used to address the issue of averaging time in the context of maintaining a maximum allowable uncertainty level. Also, a maximum error requirement in the vehicle’s installation is suggested to allow the use of rapid but approximate vehicle alignment methods without incurring errors that exceed the data uncertainty. Observed reproducibility results are presented spanning a 16 month period.
Technical Paper

Transient CFD Simulations of a Bell Sprayer

1998-09-29
982291
A methodology is developed that incorporates high resolution CFD flowfield information and a particle trajectory simulation, aimed at addressing Paint Transfer Efficiency (PTE) for bell sprayers. Given a solid model for the bell sprayer, the CFD simulation, through automeshing, determines a high resolution Cartesian volume mesh (14-20 million cells). With specified values of the initial shaping air, transient and steady-state flow field information is obtained. A particle trajectory visualization tool called SpraySIM uses this complicated flowfield information to determine the particle trajectories of the paint particles under the influence of drag, gravity and electrostatic potential. The sensitivity of PTE on shaping air velocity, charge-to-mass ratio, potential, and particle diameter are examined.
Technical Paper

Ting Noise Generation in Automotive Applications

2017-03-28
2017-01-1121
Automobile customers are looking for higher performance and quieter comfortable rides. The driveline of a vehicle can be a substantial source of NVH issues. This paper provides an understanding of a driveline noise issue which can affect any variant of driveline architecture (FWD, AWD, RWD and 4X4). This metallic noise is mostly present during the take-off and appropriately termed as ting noise. This noise was not prevalent in the past. For higher fuel economy, OEMs started integrating several components for lighter subsystems. This in effect made the system more sensitive to the excitation. At present the issue is addressed by adding a ting washer in the interface of the wheel hub bearings and the halfshafts. This paper explains the physics behind the excitation and defines the parameters that influence the excitation. The halfshaft and the wheel hub are assembled with a specified hub nut torque.
Technical Paper

Three-Dimensional Simulations of Automotive Catalytic Converter Internal Flow

1991-02-01
910200
The three-dimensional non-reacting flow field inside a typical dual-monolith automotive catalytic converter was simulated using finite difference analysis. The monolithic brick resistance was formulated from the pressure gradient of fully developed laminar duct-flow and corrected for the entrance effect. This correlation was found to agree with experimental pressure drop data, and was introduced as an additional source term into the non-dimensional momentum governing equation within the brick. Flow distribution within the monolith was found to depend strongly on the diffuser performance, which is a complex function of flow Reynolds number, brick resistance, and inlet pipe length and bending angles. A distribution index was formulated to quantify the degree of non-uniformity at selected test cases covering ranges of flow conditions, brick types, and inlet conditions.
Technical Paper

The Application of a One-Way Coupled Aerodynamic and Multi-Body Dynamics Simulation Process to Predict Vehicle Response during a Severe Crosswind Event

2017-03-28
2017-01-1515
Industry trends towards lighter, more aerodynamically efficient road vehicles have the potential to degrade a vehicle’s response to crosswinds. In this paper, a methodology is outlined that indirectly couples a computational fluid dynamics (CFD) simulation of the vehicle’s aerodynamic characteristics with a multi-body dynamics simulation (MBD) to determine yaw, roll and pitch response characteristics during a severe crosswind event. This one-way coupling approach mimics physical test conditions outlined in open loop test procedure ISO 12021:2010 that forms part of the vehicle sign-off criterion at Ford Motor Company. The methodology uses an overset mesh CFD method to drive the vehicle through a prescribed crosswind event, providing unfiltered predictions of vehicle force and moment responses that are used as applied forces in the MBD model. The method does not account for changes in vehicle attitude due to applied aerodynamic forces and moments.
Technical Paper

The Aerodynamic Development of the Probe IV Advanced Concept Vehicle

1983-06-06
831000
The aerodynamic development and characteristics of a four-passenger advanced concept automobile are described. An overview of the areas of the vehicle design which were dealt with to obtain a drag coefficient value of 0.153 is provided. The interior packaging philosophy is outlined which led to the potential for packaging four to six passengers within an extremely low drag automobile. Parametric shape studies of the major surface design elements are documented from the contributing development testing. The particular design treatments adopted and the rationale behind the choice of design are examined for each of the aerodynamically-sensitive areas of the vehicle. Examinations of the unique solutions to vehicle cooling, ramp and curb clearance, front wheel skirting and vehicle attitude are presented. Full scale wind tunnel data is shown for the configurations examined and vehicle stability parameters compared with conventional vehicles.
Technical Paper

THE INTERSTATE HIGHWAY SYSTEM SUPER TRANSPORT TRUCK

1965-02-01
650160
This paper describes the design and build of an experimental super transport truck for high-speed, long distance freight hauling on the interstate highway system of the 1970's. The tractor, powered by a 600-hp gas turbine engine, pulls two 40-foot tandem axle trailers at a G.C.W. of 170,000 lbs. Details of the turbine engine development are covered in SAE paper, No. 991B. One of the features of the super transport truck is the cab, which is designed for long-distance, non-stop, two-man operation. It is provided with sleeping accommodations, washroom conveniences, food facilities, and a complete heating and air-conditioning system. The 13-foot high cab roof is flush with the top of the trailers, providing a substantial aerodynamic advantage. Other features and components of the truck are described, and observations made during the 5500-mile national tour are discussed.
Technical Paper

System Level Durability Engineering in CAE

2006-03-01
2006-01-1981
This paper will discuss the vehicle top-down design approach that includes the non-linearity and sub-system interactions such as tire and road, (left and right) interaction between two or more parts connected by bushings, springs, bolts, stabilizer-bar, etc… The proposed method would allow for the inclusion of realistic boundary conditions and proper load simulation, and it would provide the ability to visualize and evaluate dynamic structural phenomena and complex component interaction. This approach would also facilitate the evaluation of design changes that may affect load propagation and/or load magnitude. All of the advantages of the sub-system analysis method mentioned above would allow for a greater understanding of the sub-system as a whole and help correctly identify the design requirements needed for the individual components that make up such chassis subsystems.
Technical Paper

Subjective Quantification of Wind Buffeting Noise

1999-05-17
1999-01-1821
It is well known that customer perception of the annoyance of steady-state wind noise can be fairly well characterized by calculating the loudness of such sounds. Commonly used is the ISO532B or Zwicker method [1]. What is not known, however, is how a customer would react to time-varying wind noise. Such situations can occur when a vehicle experiences cross-wind conditions on the highway. Turbulent air flow generated by either a passing vehicle or when traveling in the wake of another vehicle can cause the wind noise to take on time-varying characteristics. The time-varying wind noise created by such situations is commonly referred to as “buffeting.” Customer complaint field data indicates that wind buffeting is a source of annoyance, but the level of the effect has never been quantified. In this study, binaural sounds were recorded inside an aeroacoustic wind tunnel. Varying degrees of buffeting were simulated using a “blocker” vehicle situated in front of the test vehicle.
Technical Paper

Simulation of Flow Control Devices in Support of Vehicle Drag Reduction

2018-04-03
2018-01-0713
Flow control devices can enable vehicle drag reduction through the mitigation of separation and by modifying local and global flow features. Passive vortex generators (VG) are an example of a flow control device that can be designed to re-energize weakly-attached boundary layers to prevent or minimize separation regions that can increase drag. Accurate numerical simulation of such devices and their impact on the vehicle aerodynamics is an important step towards enabling automated drag reduction and shape optimization for a wide range of vehicle concepts. This work demonstrates the use of an open-source computational-fluid dynamics (CFD) framework to enable an accurate and robust evaluation of passive vortex generators in support of vehicle drag reduction. Specifically, the backlight separation of the Ahmed body with a 25° slant is used to evaluate different turbulence models including variants of the RANS, DES, and LES formulations.
Technical Paper

Shape Optimization of IC Engine Ports and Chambers

1998-02-23
980127
Intense competition and global regulations in the automotive industry has placed unprecedented demands on the performance, efficiency, and emissions of today's IC engines. The success or failure of a new engine design to meet these often-conflicting requirements is primarily dictated by its capability to provide minimal restriction for the inducted and exhausted flow and by its capability to generate strong large-scale in-cylinder motion. The first criterion is directly linked to power performance of the engine, while the latter has been shown to control the burn rate in IC engines. Enhanced burn rates are favorable to engine efficiency and partial load performance. CFD based Numerical Simulations have recently made it possible to study the development of such engine flows in great details. However, they offer little guidance for modifying the ports and chamber geometry controlling the flow to meet the desired performance.
Technical Paper

Selective Galvanizing Using Kinetic Spraying

2003-03-03
2003-01-1237
General corrosion protection of sheet materials such as steel used in automobile construction has reached a high level of performance, due primarily to the incorporation of mill-applied treatments such as electrogalvanizing, galvannealing and other coil-coating processes developed over the last half century. While such treatments have greatly extended the corrosion resistance of steel and its various body constructs, attention is now focused on aspects of the manufacturing process wherein these intended protections are compromised by such features as weldments, joins, cut edges and extreme metal deformations such as hems. A novel metal deposition process, based on high-velocity impact fusion of solid metal particles, has been used to extend the corrosion resistance of base steel and pre-galvanized sheet, by selectively placing highly controlled depositions of zinc and other sacrificial materials in close proximity to critical manufacturing details.
Technical Paper

Root Cause Identification and Methods of Reducing Rear Window Buffeting Noise

2007-05-15
2007-01-2402
Rear Window Buffeting (RWB) is the low-frequency, high amplitude, sound that occurs in many 4-door vehicles when driven 30-70 mph with one rear window lowered. The goal of this paper is to demonstrate that the mechanisms of RWB are similar to that of sun roof buffeting and to describe the results of several actions suspected in contributing to the severity of RWB. Finally, the results of several experiments are discussed that may lend insight into ways to reduce the severity of this event. A detailed examination of the side airflow patterns of a small Sport Utility Vehicle (SUV) shows these criteria exist on a small SUV, and experiments to modify the SUV airflow pattern to reduce RWB are performed with varying degrees of success. Based on the results of these experiments, design actions are recommended that may result in the reduction of RWB.
Technical Paper

Resistance Spot Weldability of Three Metal Stack Dual Phase 600 Hot-dipped Galvanized Steel

2007-04-16
2007-01-1363
Fuel economy and federal safety regulations are driving automotive companies to use Dual Phase and other Advanced High Strength Steels (AHSS) in vehicle body structures. Joining and assembly plays a crucial role in the selection of these steels. Specifications are available for the resistance spot welding (RSW) of lower strength sheet steels, covering many aspects of the welding process from the stabilization procedure to endurance testing. Currently, specifications in the automotive industry for RSW with AHSS are limited. It is well known that welding of a thickness ratio greater than 1:2 poses a challenge. To utilize thinner gauge AHSS panels on body-in-white, welding schedules to join the thin to thick sheet steel stack-up are needed. Most of the existing published work was conducted on uncoated sheets and welded to the same thickness.
Journal Article

Rapid Meshing for CFD Simulations of Vehicle Aerodynamics

2009-04-20
2009-01-0335
To-date the primary challenge in conducting aerodynamic CFD simulations of actual vehicles with realistically complex geometry has been the construction of a computational mesh. The CAD-to-Mesh processes used to-date have been laborious, often requiring many weeks of engineering time. In this paper we present a new technique to greatly expedite the CAD-to-Mesh process. The fundamentals of this technique are discussed followed by case studies that show that this technique can reduce the engineering time required for the CAD-to-Mesh process to just a few hours.
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