Development of a Numerical Investigation Framework for Ground Vehicle Platooning

Charles Patrick Bounds,Mesbah Uddin,Sudhan Rajasekar

doi:10.3390/fluids6110404

Charles Patrick Bounds, Mesbah Uddin + Show 1 more

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https://doi.org/10.3390/fluids6110404

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Abstract

This paper presents a study on the flow dynamics involving vehicle interactions. In order to do so, this study first explores aerodynamic prediction capabilities of popular turbulence models used in computational fluid dynamics simulations involving tandem objects and thus, ultimately presents a framework for CFD simulations of ground vehicle platooning using a realistic vehicle model, DrivAer. Considering the availability of experimental data, the simulation methodology is first developed using a tandem arrangement of surface-mounted cubes which requires an understanding on the role of turbulence models and the impacts of the associated turbulence model closure coefficients on the prediction veracity. It was observed that the prediction accuracy of the SST k−ω turbulence model can be significantly improved through the use of a combination of modified values for the closure coefficients. Additionally, the initial validation studies reveal the inability of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach to resolve the far wake, and its frailty in simulating tandem body interactions. The Improved Delayed Detached Eddy Simulations (IDDES) approach can resolve the wakes with a reasonable accuracy. The validated simulation methodology is then applied to the fastback DrivAer model at different longitudinal spacing. The results show that, as the longitudinal spacing is reduced, the trailing car’s drag is increased while the leading car’s drag is decreased which supports prior explanations of vortex impingement as the reason for drag changes. Additionally, unlike the case of platooning involving Ahmed bodies, the trailing model drag does not return to an isolated state value at a two car-length separation. However, the impact of the resolution of the far wake of a detailed DrivAer model, and its implication on the CFD characterization of vehicle interaction aerodynamics need further investigations.

Highlights

In recent years, the influence of climate change and a push toward sustainable environmental practices have begun to change the face of the automotive industry
The three turbulence models chosen for this investigation included Realizable k − e (RKE) [23], SST Menter k − ω (SST) [25], and v2 − f (V2F) [27] models
When comparing the two cases, good agreement is seen between the large-scale flow features, such as the vortex core positions, with the only main disagreements occurring in the amount of separation over the top face of the leading cube which was already noted in the isolated case to be over predicted by the Improved Delayed Detached Eddy Simulations (IDDES) model

Summary

Introduction

The influence of climate change and a push toward sustainable environmental practices have begun to change the face of the automotive industry. Ashton et al [20] compared the DES methods to the RANS simulation methods and found that the IDDES SST k − ω improved the drag prediction but still overestimated the recirculation length due to an over-prediction of TKE in the initial separation With all this considered, the DrivAer geometry provides a great platform for a fully detailed platooning simulation which will be performed in this paper. The geometry has one drawback, because of its relatively recent release, large amounts of data are not available as they are for some older testing geometries like a surface mounted cube or Ahmed body To address this problem, this paper seeks to create a high fidelity CFD simulation framework which can be used for the testing of detailed car geometries in a platooning scenario. Once the methodology has been established, the same procedure will be applied to the DrivAer model simulations

Governing Equations

Computational Setup and Boundary Conditions

Results and Discussion

Conclusions