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Technical Paper

Comparison Between the Conventional Body-Fitted and the Lattice Boltzmann CFD Methods for the Flow around a Generic Pickup Truck

Computational Fluid Dynamics (CFD) has gained popularity as a tool for many airflow situations including road vehicle aerodynamics. This trend, to bring CFD to bear on vehicle aerodynamic design issues, is appropriate and timely in view of the increasing competitive and regulative pressures being faced by the automotive industry. For a large portion of the engineering community, the primary source of CFD capabilities is through the purchase of commercial CFD codes. This paper summarizes the results of a series of benchmark external aerodynamic simulations that were carried out for a generic pickup truck model using two commercial CFD codes, namely Fluent and the PowerFLOW. For direct comparisons the computations and the experiments were performed for the same model (vehicle) geometry and under similar flow conditions.
Technical Paper

Numerical Investigation of Road Vehicle Aerodynamics Using the Immersed Boundary RANS Approach

This paper describes the computational results of the flow field around two vehicle geometries using the Immersed Boundary (IB) technique in conjunction with a steady RANS CFD solver. The IB approach allows the computation of the flow around objects without requiring the grid lines to be aligned with the body surfaces. In the IB approach instead of specifying body boundary conditions, a body force is introduced in the governing equations to model the effect of the presence of an object on the flow. This approach reduces the time necessary for meshing and allows utilization of more efficient and fast CFD solvers. The simulations are carried out for an SUV and a pickup truck models at a Reynolds number of 8×105. Cartesian meshes (non-uniform) with local grid refinement are used to increase the resolution close to the boundaries. The simulation results are compared with the existing measurements in terms of surface pressures, velocity profiles, and drag coefficients.
Journal Article

Aerodynamics of a Pickup Truck: Combined CFD and Experimental Study

This paper describes a computational and experimental effort to document the detailed flow field around a pickup truck. The major objective was to benchmark several different computational approaches through a series of validation simulations performed at Clemson University (CU) and overseen by those performing the experiments at the GM R&D Center. Consequently, no experimental results were shared until after the simulations were completed. This flow represented an excellent test case for turbulence modeling capabilities developed at CU. Computationally, three different turbulence models were employed. One steady simulation used the realizable k-ε model. The second approach was an unsteady RANS simulation, which included a turbulence closure model developed in-house. This simulation captured the unsteady shear layer rollup and breakdown over the front of the hood that was expected and seen in the experiments but unattainable with other off-the-shelf turbulence models.
Journal Article

Wind Noise Measurements for Automotive Mirrors

In order to understand the flow and wind noise characteristics generated by the outside rearview (OSRV) mirror, a series of wind noise measurements for two production mirrors was conducted at the GM Aerodynamics Lab (GMAL) wind tunnel. These measurements included the time-averaged static pressures, surface noise sources, and far field propagation noise. The data obtained in this investigation will be used for future CFD numerical validations. The two mirrors chosen for the test are the GMT360 (a truck mirror) and the GMX320 (a sedan mirror). The test mirror was mounted on an elevated table which was specially designed for the current project to avoid any significant flow boundary layer buildup on the wind tunnel floor. The test conditions reported in this paper include four inlet speeds of 30, 50, 70 and 90 mph at 0 yaw angle. To record the wind noise sources, nine surface flush-mount microphones were used.