Abstract
We evaluate the aerodynamic performance of several passive vortex generators (VGs) placed on a standard Ahmed body, with a slant angle (α = 35º), subjected to different yawing angles (β) using RANS-based models. Rigorous validation of the numerical results is performed with previously published experimental data for (β ≤ 8º) for the Ahmed body. Our model results depict a good overall agreement with several experimental data sets. An array of different vortex generators such as the delta-winglet (DVGs), the cylindrical (CVGs) and trapezoidal (TVGs) types are introduced on to the validated model. The introduction of CVGs and DVGs tends to have a beneficial aerodynamic performance for (β = 0º). In contrast, the TVGs tend to impair the performance by producing massive flow separation over the slant for (β = 0º). Conversely, for (β > 0º), a swift transition happens with TVGs wherein the high-energy streamwise vortices that are produced tend to improve the pressure footprint, thereby reducing the overall drag. A deterioration in the performance of DVGs is predicted during (β > 4º), wherein the ‘c’-pillar vortex on the leeward side interferes with the streamwise vortical structure, which adversely influences the flow over the roof-slant edge. Overall, a maximum of ~ 8.5% and ~ 7.7% drag reduction appears to be possible with the designed CVGs and TVGs at smaller vehicle yawing conditions.
Highlights
Drag reduction techniques on standard aerodynamic vehicles are of significant interest to automobile manufacturers owing to higher repeatability and provide an enhanced understanding of the fuel consumption to protect the global environment
Effect of VGs on Ahmed Body” section details the numerical simulations of several vortex generators such as the deltawinglet-type vortex generators (DVGs), cylindrical vortex generators (CVGs) and trapezoidal vortex generators (TVGs) on the baseline Ahmed body when subjected to several yaw angles (β); conditions that lead to both their performance enhancement and deterioration are critically examined. “6
The validation of the numerical results is followed by embedding the commonly employed, small vortex generators (VG) structures such as the delta-winglet (DVG), cylindrical (CVG) and trapezoidal (TVG) types on the baseline configuration subjected to different values of (β); the outcomes are as follows: (1) The DVGs show beneficial trend in terms of drag reduction for (β ≤ 4o), beyond which the streamwise vortices produced by the DVGs tend to interfere with c-pillar vortex on the leeward side adversely
Summary
Drag reduction techniques on standard aerodynamic vehicles are of significant interest to automobile manufacturers owing to higher repeatability and provide an enhanced understanding of the fuel consumption to protect the global environment. It explored the effects of two different types of vortex generators, namely the ‘bump’ shape and the delta-winglet type on a realistic sedan vehicle, the Mitsubishi LANCER EVOLUTION VIII Their findings provided significant insight into the optimum height of the VGs being equal to the thickness of the boundary layer and a meaningful reduction in both the drag and lift coefficients through the application of VGs. the surface pressures on the rear of the vehicle appeared to enhance with the presence of VGs indicating a delay in flow separation compared to a standard car. Effect of VGs on Ahmed Body” section details the numerical simulations of several vortex generators such as the DVGs, CVGs and TVGs on the baseline Ahmed body when subjected to several yaw angles (β); conditions that lead to both their performance enhancement and deterioration are critically examined. Conclusions” section summarizes the critical contributions and findings from this study
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