Fred Browand

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.

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 Forces on Truck Models, Including Two Trucks in Tandem

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERSITY OF CALIFORNIA, BERKELEY Aerodynamic Forces on Truck Models, Including Two Trucks in Tandem Mustapha Hammache, Mark Michaelian, Fred Browand University of Southern California California PATH Research Report UCB-ITS-PRR-2001-27 This work was performed as part of the California PATH Program of the University of California, in cooperation with the State of California Business, Transportation, and Housing Agency, Department of Transportation; and the United States Department of Transportation, Federal Highway Administration. The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California. This report does not constitute a standard, specification, or regulation. Report for MOU 387, TO 4214 October 2001 ISSN 1055-1425 CALIFORNIA PARTNERS FOR ADVANCED TRANSIT AND HIGHWAYS

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.

Fuel Savings by Means of Flaps Attached to the Base of a Trailer: Field Test Results

This paper presents field test results for fuel savings by means of flat flaps attached to the base of a standard semi trailer. The flaps are constructed from a fiberglass- epoxy-resin material and have a length equal to one-quarter of the trailer-base width (about 61 cm or 2 feet). They are attached along the rear door hinge lines on either side of the trailer and along the trailer roof-line so that no gap appears at the joint between the flap and the trailer base. The flap angle is variable and can be set to 10, 13, 16, 19 or 22 degrees. Tests were conducted in May 2004 at the NASA Crows Landing Flight Facility in the northern San Joaquin Valley, California.

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.

Base Flaps and Oscillatory Perturbations to Decrease Base Drag

The objective of this investigation is to study possible means for reducing the base drag of a tractor-trailer. The experiments are conducted in the Dryden wind tunnel at the USC Ground Vehicle Aerodynamics Laboratory. A roughly 1/15 scale model resembling a trailer is utilized for the study. The model is fitted with a shaped nose-piece to ensure attached flow over the forward portion of the model. The model is equipped with a force balance to measure drag. In addition base pressures are measured, and hot-wire wake surveys are conducted downstream from the model base. The Reynolds numbers (based on the square-root of the model cross-sectional area), range from 0.1 × 106 to 0.4 × 106.

Drag Forces Experienced by Two, Full-Scale Vehicles at Close Spacing

The present study aims to document the drag reduction for a two-vehicle platoon by operating two full-scale Ford Windstar vans in tandem on a desert lakebed. Drag forces are measured with the aid of a special tow bar force measuring system designed and manufactured at USC. The testing procedure consists of a smooth acceleration, followed by a smooth deceleration of the platoon. Data collected during acceleration allows the calculation of the drag force on the trail-vehicle, while data collected during deceleration is used to calculate the drag on the lead vehicle. Results from the full-scale tests show that the drag behaviors for the two vans are in general agreement with the earlier conclusions drawn from the wind tunnel tests--namely, both vans experience substantial drag savings at spacings of a fraction of a car length.

Flow Structure in the Gap between Two Bluff Bodies

The flow in the gap between two bluff bodies that together resemble a model tractortrailer is investigated using Particle Image Velocimetry (PIV). The velocity field in the gap is experimentally observed to persist for periods of time in an essentially symmetric state or in an asymmetric state. A classification of velocity fields based on a Proper Orthogonal Decomposition (POD) of the flow is performed and the two most energetic basic states are shown to be these same symmetric and asymmetric states. As the flow moves between symmetric and asymmetric conditions, the contribution of the various eigenmodes is demonstrated. Flow states in the symmetric condition can be further subdivided into those transitional states which mark a movement of the flow between asymmetries and those symmetric steady states in which the flow may rest for longer periods of time.

In-situ swinging arm calibration for hot-film anemometers

A method of calibration for hot-film anemometers is presented. A swinging arm that moves under the influence of gravity serves as both a calibration mechanism and a probe support. The velocity of the probe is found by differentiating the angular position history of the arm and multiplying it with the arm length. Limitations on the quality of calibration data while the arm is accelerating are discussed. The hot film voltage output is then matched to the velocity to find the two constants in Kings law. The calibration was tested by taking velocity profile measurements in a laminar boundary layer. The results of these compared well to the Blasius profile.