Wake Analysis and Drag Reduction for a Square Back Ahmed Body Using LES Computations

The trend of automotive design induces vertical shape in the region of the rear tailgate, which leads to important aerodynamic losses in the rear back of vehicles. Experimental wake analysis performed behind a square back bluff body shows influence of the vortex transport in the mixing layers backward the detachment region. It is therefore important to carry on studies on turbulent wake understanding in order to find solutions for drag reduction with the current vehicle design. This paper presents LES simulation results computed in order to describe transport of large vortices produced in the 3D wake structure behind a square back bluff body. Prior to this result analysis, we will show comparison with experimental results, helpful to validate these transient computations, performed with different pulsed jets implemented at the top end of the square back, close to the separation zone. Analysis of these computations results will also focus on the relation between amplitude of the flow structure and Cd results.

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CFD Based Investigations into Optimization of Diffuser Angle on Rear Bus Body

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.836.127 ◽

2016 ◽

Vol 836 ◽

pp. 127-131 ◽

Cited By ~ 2

Author(s):

Wawan Aries Widodo ◽

Mutiara Nuril Karohmah

Keyword(s):

Fluid Flow ◽

Lift Force ◽

Bluff Body ◽

Cfd Simulation ◽

Aerodynamic Forces ◽

Wake Structure ◽

Bus Body ◽

Simulation Results ◽

Drag And Lift ◽

Diffuser Angle

Fluid flow interaction around bluff body to create aerodynamic forces including drag and lift force. The strategy to improve arodynamic forces to modify the shape of rear body. This investigation is conducted to simulate fluid flow past a bus body with variation of diffuser angle on the rear. The diffuser angle was set to 0°, 6°, 12°, and 18°, respectively. The CFD simulation results shown that diffuser on rear body bus models able to improve the aerodynamic forces and wake structure are correspond with incresing diffuser angle. The drag coefficient was reduced until 2.3% is related with diffuser angle (β) 180, also, diffuser angle (β) 120 capable to increase downforce significantly until ten times are compared with zero diffuser angle.

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MHD bluff body turbulent wake stabilization

Magnetohydrodynamics ◽

10.22364/mhd.39.3.9 ◽

2003 ◽

Vol 39 (3) ◽

pp. 283-290

Keyword(s):

Bluff Body ◽

Turbulent Wake

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Numerical study of the flow over the modified simple frigate shape

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020977752 ◽

2020 ◽

pp. 095441002097775

Author(s):

Tong Li ◽

Yibin Wang ◽

Ning Zhao

Keyword(s):

Bluff Body ◽

Recirculation Zone ◽

Numerical Study ◽

Reference Value ◽

Flow Fields ◽

Navier Stokes ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Simulation Results

The simple frigate shape (SFS) as defined by The Technical Co-operative Program (TTCP), is a simplified model of the frigate, which helps to investigate the basic flow fields of a frigate. In this paper, the flow fields of the different modified SFS models, consisting of a bluff body superstructure and the deck, were numerically studied. A parametric study was conducted by varying both the superstructure length L and width B to investigate the recirculation zone behind the hangar. The size and the position of the recirculation zones were compared between different models. The numerical simulation results show that the size and the location of the recirculation zone are significantly affected by the superstructure length and width. The results obtained by Reynolds-averaged Navier-Stokes method were also compared well with both the time averaged Improved Delayed Detached-Eddy Simulation results and the experimental data. In addition, by varying the model size and inflow velocity, various flow fields were numerically studied, which indicated that the changing of Reynolds number has tiny effect on the variation of the dimensionless size of the recirculation zone. The results in this study have certain reference value for the design of the frigate superstructure.

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Manipulation of three-dimensional asymmetries of a turbulent wake for drag reduction

Journal of Fluid Mechanics ◽

10.1017/jfm.2020.1133 ◽

2021 ◽

Vol 912 ◽

Author(s):

Yann Haffner ◽

Thomas Castelain ◽

Jacques Borée ◽

Andreas Spohn

Keyword(s):

Drag Reduction ◽

Three Dimensional ◽

Turbulent Wake

Abstract

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Automotive Drag Reduction through Distributed Base Roughness Elements

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.553.267 ◽

2014 ◽

Vol 553 ◽

pp. 267-272

Author(s):

Iain Robertson ◽

Adrien Becot ◽

Adrian Gaylard ◽

Ben Thornber

Keyword(s):

Drag Reduction ◽

Reference Model ◽

Detailed Examination ◽

Rear Face ◽

Cfd Simulations ◽

Near Wake ◽

Wake Structure ◽

Pressure Drag ◽

Roughness Elements ◽

Baseline Case

This paper focuses on the effect of base roughness added to the rear of an automotive reference model, the Windsor model. This roughness addition was found to reduce both the drag and the lift of the model. RANS CFD simulations presented here replicate the experimentally observed drag reduction and enable a detailed examination of the mechanisms behind this effect. Investigations into the wake structure of the configurations with base roughness and the baseline case without base roughness showed the main changes to the wake to include a reduction in the overall size of the wake with base roughness present. Furthermore a reduction in the near wall velocities at the rear of the model caused stretching of the upper and lower vortices, a more turbulent near wake and pressure recovery over much of the rear face. This leads to reduce levels of pressure drag on the model.

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Lattice Boltzmann study on drag reduction of a bluff body by slip boundary

Journal of Physics Conference Series ◽

10.1088/1742-6596/1300/1/012036 ◽

2019 ◽

Vol 1300 ◽

pp. 012036

Author(s):

Liuming Yang ◽

Yuan Gao ◽

Shuai Zhao ◽

Yang Yu ◽

Guoxiang Hou

Keyword(s):

Drag Reduction ◽

Lattice Boltzmann ◽

Bluff Body ◽

Slip Boundary

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Bionic shape design of electric locomotive and aerodynamic drag reduction

Archives of Transport ◽

10.5604/01.3001.0012.8369 ◽

2018 ◽

Vol 4 (48) ◽

pp. 99-109

Author(s):

Zhenfeng WU ◽

Yanzhong HUO ◽

Wangcai DING ◽

Zihao XIE

Keyword(s):

Flow Field ◽

Drag Reduction ◽

Bluff Body ◽

Aerodynamic Drag ◽

Geometric Characteristic ◽

Shape Design ◽

Shape Optimisation ◽

Electric Locomotive ◽

Geometric Models ◽

Characteristic Lines

Bionics has been widely used in many fields. Previous studies on the application of bionics in locomotives and vehicles mainly focused on shape optimisation of high-speed trains, but the research on bionic shape design in the electric locomotive field is rare. This study investigated a design method for streamlined electric locomotives according to the principles of bionics. The crocodiles were chosen as the bionic object because of their powerful and streamlined head shape. Firstly, geometric characteristic lines were extracted from the head of a crocodile by analysing the head features. Secondly, according to the actual size requirements of the electric locomotive head, a free-hand sketch of the bionic electric locomotive head was completed by adjusting the position and scale of the geometric characteristic lines. Finally, the non-uniform rational B-splines method was used to establish a 3D digital model of the crocodile bionic electric locomotive, and the main and auxiliary control lines were created. To verify the drag reduction effect of the crocodile bionic electric locomotive, numerical simulations of aerodynamic drag were performed for the crocodile bionic and bluff body electric locomotives at different speeds in open air by using the CFD software, ANSYS FLUENT16.0. The geometric models of crocodile bionic and bluff body electric locomotives were both marshalled with three cars, namely, locomotive + middle car + locomotive, and the size of the two geometric models was uniform. Dimensions and grids of the flow field were defined. And then, according to the principle of motion relativity, boundary conditions of flow field were defined. The results indicated that the crocodile bionic electric locomotive demonstrated a good aerodynamic performance. At the six sampling speeds in the range of 40–240 km/h, the aerodynamic drag coefficient of the crocodile bionic electric locomotive decreased by 7.7% on the average compared with that of the bluff body electric locomotive.

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