Bluff Body Overflow and Drag Reduction Control

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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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

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Experimental Study on Bluff Body Drag Reduction with Fluidic Oscillators

52nd Aerospace Sciences Meeting ◽

10.2514/6.2014-0403 ◽

2014 ◽

Cited By ~ 26

Author(s):

Rene Woszidlo ◽

Timo Stumper ◽

C. Nayeri ◽

Christian O. Paschereit

Keyword(s):

Experimental Study ◽

Drag Reduction ◽

Bluff Body ◽

Body Drag

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Drag reduction by closed-loop control of a separated flow over a bluff body with a blunt trailing edge

Proceedings of the 44th IEEE Conference on Decision and Control ◽

10.1109/cdc.2005.1582204 ◽

2006 ◽

Cited By ~ 14

Author(s):

L. Henning ◽

R. King

Keyword(s):

Drag Reduction ◽

Bluff Body ◽

Closed Loop ◽

Separated Flow ◽

Closed Loop Control ◽

Trailing Edge ◽

Loop Control ◽

Blunt Trailing Edge

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Microfiber Coating for Flow Control over a Blunt Surface

Coatings ◽

10.3390/coatings9100664 ◽

2019 ◽

Vol 9 (10) ◽

pp. 664 ◽

Cited By ~ 1

Author(s):

Mitsugu Hasegawa ◽

Hirotaka Sakaue

Keyword(s):

Drag Reduction ◽

Flow Control ◽

Bluff Body ◽

Relative Length ◽

Control Device ◽

Cylinder Surface ◽

Passive Flow Control ◽

Passive Flow ◽

Maximum Drag Reduction ◽

The Impact

A microfiber coating having a hair-like structure is investigated as a passive flow control device of a bluff body. The effect of microfiber length is experimentally studied to understand the impact of the coating on drag on a cylinder. A series of microfiber coatings with different lengths are fabricated using flocking technology and applied to various locations over the cylinder surface under the constant Reynolds number of 6.1 × 104 based on the diameter of the cylinder. It is found that the length and the location both play important roles in the drag reduction. Two types of drag reduction can be seen: (1) when the relative length of the microfiber, k/D, is less than 1.8%, and the coating is applied before flow separates over the cylinder; and (2) k/D is over 3.3%, and the coating is applied after the flow separation location on the cylinder. The maximum drag reduction for the former type is 59% compared to that from the cylinder without the microfiber coating. For the latter type, the maximum drag reduction is 27%.

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Reinforcement learning for bluff body active flow control in experiments and simulations

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2004939117 ◽

2020 ◽

Vol 117 (42) ◽

pp. 26091-26098

Author(s):

Dixia Fan ◽

Liu Yang ◽

Zhicheng Wang ◽

Michael S. Triantafyllou ◽

George Em Karniadakis

Keyword(s):

Reinforcement Learning ◽

Fluid Mechanics ◽

Drag Reduction ◽

Flow Control ◽

Bluff Body ◽

Control Strategies ◽

Active Flow Control ◽

Reduction Process ◽

Automatic Sequence ◽

Active Flow

We have demonstrated the effectiveness of reinforcement learning (RL) in bluff body flow control problems both in experiments and simulations by automatically discovering active control strategies for drag reduction in turbulent flow. Specifically, we aimed to maximize the power gain efficiency by properly selecting the rotational speed of two small cylinders, located parallel to and downstream of the main cylinder. By properly defining rewards and designing noise reduction techniques, and after an automatic sequence of tens of towing experiments, the RL agent was shown to discover a control strategy that is comparable to the optimal strategy found through lengthy systematically planned control experiments. Subsequently, these results were verified by simulations that enabled us to gain insight into the physical mechanisms of the drag reduction process. While RL has been used effectively previously in idealized computer flow simulation studies, this study demonstrates its effectiveness in experimental fluid mechanics and verifies it by simulations, potentially paving the way for efficient exploration of additional active flow control strategies in other complex fluid mechanics applications.

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