James C. Ross

The aerodynamics of heavy vehicles : trucks, buses, and trains

Aerodynamics and Other Efficiencies in Transporting Goods.- Commercial Vehicle Aerodynamic Drag Reduction: Historical Perspective as a Guide.- The Status of Detached-Eddy Simulation for Bluff Bodies.- Exploring the Flow Around a Simplified Bus with Large Eddy Simulation and Topological Tools.- Unsteady Flow Around Cylinders with Cavities.- Complex CFD for Everyday Use - Practical Applications for Vehicle Analysis.- Large Eddy Simulation of Flow Around the Ahmed Body.- Detached-Eddy Simulation of the Ground Transportation System.- Time Dependent vs. Steady State Calculations of External Aerodynamics.- Aerodynamics of Ground Vehicles - Toward Reliable and Affordable CFD.- Improved Tractor-Trailer Integration and Aerodynamics Through the Use of CFD.- Large Eddy Simulation of Turbulence Via Lattice Boltzmann Based Approach: Fundamental Physics and Practical Applications.- Aspects of CFD Application to Vehicle Aerodynamic Design.- PIV Study of the Near Wake of a Pickup Truck.- Applications of DDPIV to Studies Associated with Road Vehicles.- Molecular Tagging Velocimetry (MTV) and Its Automotive Applications.- Quantitative Flow Visualization for Large Scale Wind Tunnels.- An Experimental Study of the Generic Conventional Model (GCM) in the NASA Ames 7-by-10-Foot Wind Tunnel.- The Measurement of Wake and Gap Flows of the Generic Conventional Truck Model (GCM) Using Three-Component PIV.- On the Aerodynamics of Tractor-Trailers.- RANS Simulations of a Simplified Tractor/Trailer Geometry.- Computational Simulation of a Heavy Vehicle Trailer Wake.- Drag Reduction of Two-Dimensional Bodies by Addition of Boat Tails.- Drag Reduction of a Tractor-Trailer Using Planar Boat Tail Plates.- RANS Simulations of Passive and Active Drag Reduction Devices for a Road Vehicle.- Pneumatic Heavy Vehicle Aerodynamic Drag Reduction, Safety Enhancement, and Performance Improvement.- Base Flaps and Oscillatory Perturbations to Decrease Base Drag.- Use of Computational Aerodynamics for Commercial Vehicle Development at DaimlerChrysler.- Numerical Simulation of the Flow About a Train Model.- Adaptation of Eddy-Viscosity Turbulence Models to Unsteady Separated Flow Behind Vehicles.- Simulation of Vehicle Aerodynamics Using a Vortex Element Method.- Energetic and CFD Modeling Considerations of Thermal Management.- Measurement of Underhood Temperatures with Various Ventilations.- Measurement and Analysis of Underhood Ventilation Air Flow and Temperatures for an Off-Road Machine.- Flow Field and Thermal Management Analysis of an Armored Vehicle Engine Compartment.- Experiments and CFD in Train Aerodynamics: A Young and Turbulent Association Full of Potential.- Recent Studies of Train Slipstreams.- Aerodynamic Effects in Railway Tunnels as Speed is Increased.- Flow-Induced Vibration of High-Speed Trains in Tunnels.- How to Reduce the Cross Wind Sensitivity of Trains.- CFD Study of Side Wind Effects on a High Speed Train.- Commercial CFD Code Validation for Heavy-Vehicle External Aerodynamics Simulation.- Computational Parametric Study on External Aerodynamics of Heavy Trucks.- Applicability of the Vortex Methods for Aerodynamics of Heavy Vehicles.- Development of a Wind Tunnel Model Mounting Configuration for Heavy Duty Trucks..- A Ground-Based Research Vehicle for Base Drag Studies at Subsonic Speeds.- Splash and Spray Measurement and Control: Recent Progress in Quebec.- Wind-Tunnel Evaluation of an Aerodynamic Heat Exchanger.- Automated Driving of Trucks and Buses: Opportunities for Increasing Productivity and Safety While Reducing Fuel Use and Emissions.- Author Index.

Computational evaluation of an airfoil with a Gurney flap

A 2D numerical investigation was performed to determine the effect of a Gurney flap on a NACA 4412 airfoil. A Gurney flap is a flat plate on the order of 1 to 3 percent of the airfoil chord length, oriented perpendicular to the airfoil chord line and located at the trailing edge of the airfoil. An incompressible Navier Stokes code, INS2D, was used to calculate the flow field about the airfoil. The fully turbulent results were obtained using the Baldwin-Barth one-equation turbulence model. Gurney flap sizes of 0.5 , 1, 1.25, 1.5, 2, and 3 percent of the airfoil chord were studied. Computational results were compared with experimental results where possible. The numerical solutions show that the Gurney flap increases airfoil lift coefficient with only a slight increase in drag coefficient. Use of a 1.5 percent chord Gurney flap increases the maximum lift coefficient by approximately 0.3 and decreases the angle of attack for a given lift coefficient by more than 3 deg. The numerical solutions exhibit detailed flow structures at the trialing edge and provide a possible explanation for the increased aerodynamic performance.

Numerical Investigation of an Airfoil with a Gurney Flap

A two-dimensional numerical investigation was performed to determine the effect of a Gurney flap on a NACA 4412 airfoil. A Gurney flap is a flat plate on the order of 1–3% of the airfoil chord in length, oriented perpendicular to the chord line and located on the airfoil windward side at the trailing edge. The flowfield around the airfoil was numerically predicted using INS2D, an incompressible Navier–Stokes solver, and the one-equation turbulence model of Baldwin and Barth. Gurney flap sizes of 0.5%, 1.0%, 1.25%, 1.5%, 2.0%, and 3.0% of the airfoil chord were studied. Computational results were compared with available experimental results. The numerical solutions show that some Gurney flaps increase the airfoil lift coefficient with only a slight increase in drag coefficient. Use of a 1.5% chord length Gurney flap increases the airfoil lift coefficient by ΔCl≈0.3 and decreases the angle of attack required to obtain a given lift coefficient by ΔαL=0>−3°. The numerical solutions show the details of the flow structure at the trailing edge and provide a possible explanation for the increased aerodynamic performance.

Navier-Stokes Analysis of the Flow About a Flap Edge

The current study computationally examines one of the principal three-dimensional features of the e ow over a high-lift system, the e ow associated with a e ap edge. Structured, overset grids were used in conjunction with an incompressible Navier ‐Stokes solver to compute the e ow over a two-element highlift cone guration. The computations were run in a fully turbulent mode using the one-equation Baldwin‐Barth model. Specie c emphasis was given to the details of the e ow in the vicinity of the e ap edge, and so the geometry was simplie ed to isolate this region. The geometry consisted of an unswept wing, which spanned a wind-tunnel test section, equipped with a single-element e ap. Two e ap cone gurations were computed: a full-span and a half-span Fowler e ap. The chord-based Reynolds number was 3.7 3 10 6 for all cases. The results for the full-span e ap agreed with two-dimensional experimental results and verie ed the method. Grid topologies and related issues for the half-span e ap geometry are discussed. Results of the half-span e ap case are compared with three-dimensional experimental results, with emphasis on the e ow features associated with the e ap edge. The results show the effect of the vortex created by the e ap edge, including the impact on e ow separation and spanwise lift distribution.

Aeroacoustic measurements of slat noise on a three-dimensional high-lift system

Experimental results are presented for the aerodynamics and acoustics of an unswept wing with a half-span flap and a full-span slat. Concurrent aerodynamic and acoustic measurements were obtained for high-lift riggings representative of landing-approach configurations. Phased microphone array measurements indicate that slat gap noise is most significant for high slat deflections where the slat is lightly loaded. More specifically, the peak noise level for the 25deg slat deflection was 20 dB higher than that of the 9-deg slat deflection. Measurements of intermediate angles indicate a gradual decrease in slat noise as slat deflection is decreased. Strouhal frequency scaling of the 25deg slat configuration suggests that vortex shedding from the slat trailing edge may be an important noise mechanism. However, a non-linear relationship between slat noise level and angle of attack suggests a more complex phenomenon. Computational results detail the strength of the shear layers in the slatcove flow field. Variations in the slat-cove shear layers with slat deflection and angle of attack are presented. From correlations between the computed results and the measured acoustics, it is hypothesized that a KelvinHelmholtz instability develops in the slat cove and a feedback mechanism forms between the slat-cove and slat trailing-edge flow fields.

Progress in Reducing Aerodynamic Drag for Higher Efficiency of Heavy Duty Trucks (Class 7-8)

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California. Companion computer simulations are being performed by Sandia National Laboratories, Lawrence Livermore National Laboratory, and California Institute of Technology using state-of-the-art techniques, with the intention of implementing more complex methods in the future.

Aerodynamic performance of a drag reduction device on a full-scale tractor/trailer

The effectiveness of an aerodynamic boattail on a tractor/trailer road vehicle was measured in the NASA Ames Research Center 80- by 120-Foot Wind Tunnel. Results are examined for the tractor/trailer with and without the drag reduction device. Pressure measurements and flow visualization show that the aerodynamic boattail traps a vortex or eddy in the corner formed between the device and the rear corner of the trailer. This recirculating flow turns the flow inward as it separates from the edges of the base of the trailer. This modified flow behavior increases the pressure acting over the base area of the truck, thereby reducing the net aerodynamic drag of the vehicle. Drag measurements and pressure distributions in the region of the boattail device are presented for selected configurations. The optimum configuration reduces the overall drag of the tractor/trailer combination by about 10 percent at a zero yaw angle. Unsteady pressure measurements do not indicate strong vortex shedding, although the addition of the boattail plates increases high frequency content of the fluctuating pressure.

DOE's Effort to Reduce Truck Aerodynamic Drag Through Joint Experiments and Computations

Class 8 tractor-trailers are responsible for 11-12% of the total US consumption of petroleum. Overcoming aero drag represents 65% of energy expenditure at highway speeds. Most of the drag results from pressure differences and reducing highway speeds is very effective. The goal is to reduce aerodynamic drag by 25% which would translate to 12% improved fuel economy or 4,200 million gal/year. Objectives are: (1) In support of DOEs mission, provide guidance to industry in the reduction of aerodynamic drag; (2) To shorten and improve design process, establish a database of experimental, computational, and conceptual design information; (3) Demonstrate new drag-reduction techniques; and (4) Get devices on the road. Some accomplishments are: (1) Concepts developed/tested that exceeded 25% drag reduction goal; (2) Insight and guidelines for drag reduction provided to industry through computations and experiments; (3) Joined with industry in getting devices on the road and providing design concepts through virtual modeling and testing; and (4) International recognition achieved through open documentation and database.

Aerodynamic Drag of Heavy Vehicles (Class 7-8): Simulation and Benchmarking

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. Experimental validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California (USC). Companion computer simulations are being performed by Sandia National Laboratories (SNL), Lawrence Livermore National Laboratory (LLNL), and California Institute of Technology (Caltech) using state-of-the-art techniques.

Navier–Stokes analysis of lift-enhancing tabs on multi-element airfoils

Abstract The flow over multi-element airfoils with flat-plate lift-enhancing tabs was numerically investigated. Tabs ranging in height from 0.25 to 1.25% of the reference airfoil chord were studied near the trailing edge of the main element. The two-dimensional numerical simulation employed an incompressible Navier–Stokes solver using a structured, embedded grid topology. The effects of various tabs were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Both computed and measured results indicated that a tab in the main-element cove improved the maximum lift and lift-to-drag ratio relative to the baseline airfoil without a tab. Computed streamlines revealed that the additional turning caused by the tab may reduce the amount of separated flow on the flap. A three-element airfoil was also studied over a range of Reynolds numbers, with computed results shown to be in good agreement with experimental data.