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Rearview cameras COME INTO SIGHT

SAE Truck & Off-Highway Engineering: June 2019

Bill Visnic
  • Magazine Article
  • 19TOFHP06_06
Published 2019-06-01 by SAE International in United States

Momentum is building behind replacing mirrors with camera monitor systems as the technology edges closer to regulatory approval.

To borrow from a well-known automotive phrase, “Objects in mirror” aren't really closer than they appear-because the mirror itself appears poised to become another relic of the analog age. Long-debated since the technology quickly became more sophisticated and less costly, camera systems to replace external rearview mirrors for trucks and other on- and off-road commercial vehicles are likely just around the corner.

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Metamaterial Mirror Reflects Sound Waves in Any Direction

  • Magazine Article
  • TBMG-34386
Published 2019-05-01 by Tech Briefs Media Group in United States

Researchers have constructed a “metamirror” device capable of perfectly reflecting sound waves in any direction. The proof-of-principle demonstration is analogous to looking directly into a mirror and only seeing the person next to you instead of your own face. With a regular mirror, the light follows the Law of Reflection — it must bounce off of it at the same angle at which it entered. The same rules generally apply to sound. To break the law of reflection with sound waves, the researchers engineered a device that could precisely control amplitude (loudness) and speed throughout the entire wave.

 

Numerical Analysis Using Fast RANS Simulations and Comparison with Experimental Measurements for Closed and Open Grille Realistic Car Models

Simerics Inc.-Sujan Dhar, Yu Jiang
Published 2019-04-02 by SAE International in United States
This paper details a comprehensive CFD study of all three variants of the DrivAer car geometries: Fastback, Notchback and Estate configurations. The most realistic geometry was chosen for each of the variants; with detailed underbody, wheels and mirrors. In addition to the closed-grille standard DrivAer models, the open-grille variant has also been simulated. Simulations are performed and compared with experiments both with and without ground simulation. Mesh generation was performed without surface alterations (e.g. wrapping) using a novel Binary-Tree automatic unstructured mesher. All simulations were performed using an enhanced k-ε RANS turbulence model within Simerics MP+. A consistent modeling methodology was developed that was rigorously applied to all variants of the DrivAer model and the simulations are shown to have consistently good agreement with experimental measurements. This demonstrates the potential of using such a methodology for several different types of vehicles during the design process.In addition to presenting the methodology and the results, a thorough review was conducted and comparisons are made with the existing body of literature on the DrivAer model: including both RANS…
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Investigation of Drag Reduction Technologies for Light-Duty Vehicles Using Surface, Wake and Underbody Pressure Measurements to Complement Aerodynamic Drag Measurements

National Research Council Canada-Fenella de Souza, Arash Raeesi
Röchling Automotive SE & Co. KG-Andreas Schmitt
Published 2019-04-02 by SAE International in United States
A multi-year, multi-vehicle study was conducted to quantify the aerodynamic drag changes associated with drag reduction technologies for light-duty vehicles. Various technologies were evaluated through full-scale testing in a large low-blockage closed-circuit wind tunnel equipped with a rolling road, wheel rollers, boundary-layer suction and a system to generate road-representative turbulent winds. The technologies investigated include active grille shutters, production and custom underbody treatments, air dams, wheel curtains, ride height control, side mirror removal and combinations of these.This paper focuses on mean surface-, wake-, and underbody-pressure measurements and their relation to aerodynamic drag. Surface pressures were measured at strategic locations on four sedans and two crossover SUVs. Wake total pressures were mapped using a rake of Pitot probes in two cross-flow planes at up to 0.4 vehicle lengths downstream of the same six vehicles in addition to a minivan and a pick-up truck. A smaller rake was used to map underbody total pressures in one cross-flow plane downstream of the rear axle for three of these vehicles.The results link drag reduction due to various technologies with…
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Aeroacoustics of Heavy Duty Truck Side Mirrors - An Experimental Study

Escenda Engineering AB-Mikael Karlsson
Volvo Group Trucks Technology-Robert Larsson, Torbjörn Ågren, Zenitha Chroneer
Published 2018-06-13 by SAE International in United States
Side mirrors are a known source of aerodynamically generated noise in vehicles. In this work we focus on mirrors for heavy duty trucks, they are large, often not designed with main focus on aero-acoustics and are located in a cumbersome position on the up-right A-pillar of European trucks. First the test method itself is discussed. To allow fast and cost effective design loops a bespoke vehicle, where the powertrain is separated from the cab, is developed. This vehicle can be run on a standard test track. While running the tests the wind speed is monitored, any variations are then compensated for in the post processing allowing averaging over longer time periods. For the mirror tests the door of the vehicle was especially trimmed to reduce other transmission paths into the cab than the side window. Additionally other possible aeroacoustic sources were reduced as much as practically possible. The generated wind noise was monitored with surface microphones both on the mirror (in the wake) and on the window. Additionally arrays of microphones were placed inside the…
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Unsteady Flow Control and Wind Noise Reduction of Side-View Mirror

FAW Jie Fang Automotive Company, Ltd.-Weijiang Meng
Jilin University-Qiliang Wang, Xin Chen, Yingchao Zhang
Published 2018-04-03 by SAE International in United States
It aims to study the unsteady flow characteristic of the side-view mirror wake field, and reduce the wind noise by means of unsteady flow control. In this paper, the PIV test in a wind tunnel is used to capture the unsteady flow in the wake field of the side-view mirror, which is used to verify the accuracy of the steady simulation method with RANS after being averaged. Then LES turbulence model is used to obtain the wind noise, and the unsteady flow characteristic like vortex shedding of the side-view mirror is studied. The results show that, in the wake of the side-view mirror, there is a vortex pair similar to Karman Vortex Street. In both horizontal and vertical sections, these two vortexes are respectively separated from the upper and lower edges of the side-view mirror. Accompanied by a significantly uncertain periodic shedding, they continue to extend back until dissipating. The pressure fluctuation on the surface caused by this process is the root cause of the wind noise pressure pulsation. And the accuracy of the noise…
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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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Investigation of Interior Noise from Generic Side- View Mirror Using Incompressible and Compressible Solvers of DES and LES

Aero-Vibro Acoustics-Huadong Yao
Chalmers University of Technology-Lars Davidson
Published 2018-04-03 by SAE International in United States
Exterior turbulent flow is an important source of automobile cabin interior noise. The turbulent flow impacts the windows of the cabins to excite the structural vibration that emits the interior noise. Meanwhile, the exterior noise generated from the turbulent flow can also cause the window vibration and generate the interior noise. Side-view mirrors mounted upstream of the windows are one of the predominant body parts inducing the turbulent flow. In this paper, we investigate the interior noise caused by a generic side-view mirror. The interior noise propagates in a cuboid cavity with a rectangular glass window. The exterior flow and the exterior noise are computed using advanced CFD methods: compressible large eddy simulation, compressible detached eddy simulation (DES), incompressible DES, and incompressible DES coupled with an acoustic wave model. The last method is used to simulate the hydrodynamic and acoustic pressure separately. The pressure fluctuations of the flow and noise are imposed on the window in the computation of the interior noise, but the reversal effect of the window vibration feeding back on the flow…
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Simplifications Applied to Simulation of Turbulence Induced by a Side View Mirror of a Full-Scale Truck Using DES

Aerodynamics-Huadong Yao
Chalmers University of Technology-Lars Davidson
Published 2018-04-03 by SAE International in United States
In this paper, the turbulent flow induced by a production side-view mirror assembled on a full-scale production truck is simulated using a compressible k-ω SST detached eddy simulation (DES) approach -- the improved delayed DES (IDDES). The truck configuration consists of a compartment and a trailer. Due to the large size and geometric complexity of the configuration, some simplifications are applied to the simulation. A purpose of this work is to investigate whether the simplifications are suitable to obtain the reasonable properties of the flow near the side-view mirror. Another objective is to study the aerodynamic performances of the mirror. The configuration is simplified regarding two treatments. The first treatment is to retain the key exterior components of the truck body while removing the small gaps and structures. Furthermore, the trailer is shaped in an apex-truncated square pyramid. This simplification is proposed based on the assumption that the downstream flow near the trailer has limited effect on the flow near the mirror. To assess the influences of the simplifications, the flow fields computed from the…
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Fourier Transform Spectrometer System

  • Magazine Article
  • TBMG-28336
Published 2018-02-01 by Tech Briefs Media Group in United States

NASA's Langley Research Center and Science Applications International Corporation have developed a method of processing data from Fourier transform spectroscopy (FTS) measurements that improves upon existing methods. This method is simpler, more accurate, faster, and less expensive than previous methods. It uses less hardware and can be used with all wavelengths.