A Comparison of Bluff-Body Base-Drag Reduction by Passive Control Means

This paper is an overview of results done on bluff body road vehicle’s base drag reduction either by experimental or numerical methods. Two categories of devices are divided that prove certain degrees of effectiveness in reducing the base drag, namely passive and active. The reduction of drag coefficient achieved in existing research ranging from 5% to 50%, which varies for each method and device. However, the higher the achieved drag reduction is, the greater the compensation required is. The compensation comes in various forms to achieve the desirable drag reduction. For passive drag reduction, hump shaped bluff body with boat-tail shows significant drag reduction by 50.9% compared to the other methods. Meanwhile, one of the potential of active drag reductions is by utilizing rotating cylinder. The rotating can reduce the drag on the bluff body by influencing the separation of boundary layer. The drag can be further reduced by enhancing the rotating cylinder with surface roughness and rotation speed. A notable 23% reduction of drag coefficient using rough surface on bluff body vehicle’s is achieved compared to the smooth surface.

Download Full-text

Base Drag Reduction of 2D Bluff Body by Using Tabs at Transonic Speeds

JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES ◽

10.2322/jjsass.56.15 ◽

2008 ◽

Vol 56 (648) ◽

pp. 15-21

Author(s):

Atsushi Hashimoto ◽

Takahiro Kobayashi ◽

Yoshiaki Nakamura

Keyword(s):

Drag Reduction ◽

Bluff Body ◽

Base Drag

Download Full-text

An improvement of the base bleed unit on base drag reduction and heat energy addition as well as mass addition

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2016.08.072 ◽

2016 ◽

Vol 109 ◽

pp. 238-250 ◽

Cited By ~ 4

Author(s):

Xiaochun Xue ◽

Yonggang Yu

Keyword(s):

Drag Reduction ◽

Heat Energy ◽

Energy Addition ◽

Base Bleed ◽

Base Drag

Download Full-text

Smart Passive Control of Thermoacoustic Instability in a Bluff-Body Stabilized Combustor: A Lagrangian Analysis of Critical Structures

10.1115/1.0005139v ◽

2021 ◽

Author(s):

C P Premchand ◽

Manikandan Raghunathan ◽

Midhun Raghunath ◽

K V Reeja ◽

Sujith R I ◽

...

Keyword(s):

Bluff Body ◽

Passive Control ◽

Lagrangian Analysis ◽

Thermoacoustic Instability

Download Full-text

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

Download Full-text

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.

Download Full-text

Drag reduction of a bluff body using adaptive control methods

Physics of Fluids ◽

10.1063/1.2236305 ◽

2006 ◽

Vol 18 (8) ◽

pp. 085107 ◽

Cited By ~ 52

Author(s):

Jean-François Beaudoin ◽

Olivier Cadot ◽

Jean-Luc Aider ◽

José-Eduardo Wesfreid

Keyword(s):

Adaptive Control ◽

Drag Reduction ◽

Bluff Body ◽

Control Methods

Download Full-text

Smart Passive Control of Thermoacoustic Instability in a Bluff-Body Stabilized Combustor: A Lagrangian Analysis of Critical Structures

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-16073 ◽

2020 ◽

Author(s):

C. P. Premchand ◽

Manikandan Raghunathan ◽

Midhun Raghunath ◽

K. V. Reeja ◽

R. I. Sujith ◽

...

Keyword(s):

Wavelet Transform ◽

Flow Field ◽

Heat Release ◽

Shear Layer ◽

Heat Release Rate ◽

Release Rate ◽

Sound Production ◽

Bluff Body ◽

Passive Control ◽

Thermoacoustic Instability

Abstract The tonal sound production during thermoacoustic instability is detrimental to the components of gas turbine and rocket engines. Identifying the root cause and controlling this oscillatory instability would enable manufacturers to save in costs of power outages and maintenance. An optimal method is to identify the structures in the flow-field that are critical to tonal sound production and perform control measures to disrupt those “critical structures”. Passive control experiments were performed by injecting a secondary micro-jet of air onto the identified regions with critical structures in the flow-field of a bluff-body stabilized, dump, turbulent combustor. Simultaneous measurements such as unsteady pressure, velocity, local and global heat release rate fluctuations are acquired in the regime of thermoacoustic instability before and after control action. The tonal sound production in this combustor is accompanied by a periodic flapping of the shear layer present in the region between the dump plane (backward-facing step) and the leading edge of the bluff-body. We obtain the trajectory of Lagrangian saddle points that dictate the flow and flame dynamics in the shear layer during thermoacoustic instability accurately by computing Lagrangian Coherent Structures. Upon injecting a secondary micro-jet with a mass flow rate of only 4% of the primary flow, nearly 90% suppression in the amplitude of pressure fluctuations are observed. The suppression thus results in sound pressure levels comparable to those obtained during stable operation of the combustor. Using Morlet wavelet transform, we see that the coherence in the dominant frequency of pressure and heat release rate oscillations during thermoacoustic instability is affected by secondary injection. The disruption of saddle point trajectories breaks the positive feedback loop between pressure and heat release rate fluctuations resulting in the observed break of coherence. Wavelet transform of global heat release rate shows a redistribution of energy content from the dominant instability frequency (acoustic time scale) to other time scales.

Download Full-text