scholarly journals Passive Flow Control for Drag Reduction on a Cylinder in Cross-Flow Using Leeward Partial Porous Coatings

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 289
Author(s):  
Imogen Guinness ◽  
Tim Persoons
Keyword(s):  
Flow Control ◽  
Numerical Study ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Porous Coating ◽  
Leeward Side ◽  
Porous Coatings ◽  
Passive Flow Control ◽  
Passive Flow ◽  
The Impact

This paper presents a numerical study on the impact of partial leeward porous coatings on the drag of circular cylinders in cross-flow. Porous coatings are receiving increasing attention for their potential in passive flow control. An unsteady Reynolds-averaged Navier–Stokes model was developed that agreed well with the numerical and experimental literature. Using the two-equation shear stress transport k−ω turbulence model, 2D flow around a circular cylinder was simulated at Re = 4.2×104 with five different angles of partial leeward porous coatings and a full porous coating. For coating angles below 130∘, the coating resulted in an increase in pressure on the leeward side of the cylinder. There was a significant reduction in the fluctuation of the pressure and aerodynamic forces and a damping effect on vortex shedding. Flow separation occurred earlier; the wake was widened; and there was a decrease in turbulence intensity at the outlet. A reduction of drag between 5 and 16% was measured, with the maximum at a 70∘ coating angle. The results differed greatly for a full porous coating and a 160∘ coating, which were found to cause an increase in drag of 42% and 43%, respectively. The results showed that leeward porous coatings have a clear drag-reducing potential, with possibilities for further research into the optimum configuration.

scholarly journals Microfiber Coating for Flow Control over a Blunt Surface

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 664 ◽  
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%.

scholarly journals Passive Flow Control Around a Semi-Circular Cylinder Using Porous Coatings

2014 ◽  
Vol 6 (1) ◽  
pp. 43-60 ◽  
Author(s):  
Chloé Mimeau ◽  
Iraj Mortazavi ◽  
Georges-Henri Cottet
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Porous Coatings ◽  
Passive Flow Control ◽  
Passive Flow

A Numerical Study of the Airfoil Aerodynamic Characteristics with Porous Surface

2014 ◽  
Vol 978 ◽  
pp. 123-130
Author(s):  
Xiao Jun Xiang ◽  
Jun Li Yang
Keyword(s):  
Shock Wave ◽  
Flow Control ◽  
Flow Separation ◽  
Numerical Study ◽  
Aerodynamic Characteristics ◽  
Porous Surface ◽  
Effective Control ◽  
Passive Flow Control ◽  
Naca0012 Airfoil ◽  
Passive Flow

Numerical simulations have been done to investigate the effect of passive flow control on the flow separation and the strength of the shock wave of the NACA0012 airfoil with two types of the porous surface. It has also been discussed that which region the porous surface applied to will make better effect on the flow control. The results show that the B type of the porous surface, which has empty bottom, has effective control on the flow separation if applied to the region near behind the separation point, while the A type of the porous surface is useless. And both A and B porous surface have effect on the decreasing of the strength of the normal shock wave strength when the porosities have been applied to the region across the shock wave. And compared with A type porous surface, the effect of the control is better if B type porous surface is applied. The result has been concluded that the aerodynamic characteristics of the airfoil can be improved with B type of the porous surface. And the B type is worth to be used.

scholarly journals Passive flow control mechanisms with bioinspired flexible blades in cross-flow tidal turbines

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Stefan Hoerner ◽  
Shokoofeh Abbaszadeh ◽  
Olivier Cleynen ◽  
Cyrille Bonamy ◽  
Thierry Maître ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Cross Flow ◽  
Tidal Energy ◽  
Control Mechanisms ◽  
Passive Flow Control ◽  
Turbine Efficiency ◽  
Tidal Turbines ◽  
Passive Flow ◽  
Axial Turbines ◽  
The Cost

Abstract State-of-the-art technologies for wind and tidal energy exploitation focus mostly on axial turbines. However, cross-flow hydrokinetic tidal turbines possess interesting features, such as higher area-based power density in array installations and shallow water, as well as a generally simpler design. Up to now, the highly unsteady flow conditions and cyclic blade stall have hindered deployment at large scales because of the resulting low single-turbine efficiency and fatigue failure challenges. Concepts exist which overcome these drawbacks by actively controlling the flow, at the cost of increased mechatronical complexity. Here, we propose a bioinspired approach with hyperflexible turbine blades. The rotor naturally adapts to the flow through deformation, reducing flow separation and stall in a passive manner. This results in higher efficiency and increased turbine lifetime through decreased structural loads, without compromising on the simplicity of the design. Graphic abstract

Computational design and experimental testing of a flexible bi-stable airfoil for passive flow control

2021 ◽  
Author(s):  
Anurag Bhattacharyya ◽  
Mark Bashkawi ◽  
Se Yeon Kim ◽  
Wanzheng Zheng ◽  
Theresa Saxton-Fox ◽  
...  
Keyword(s):  
Flow Control ◽  
Experimental Testing ◽  
Computational Design ◽  
Passive Flow Control ◽  
Passive Flow

Numerical study on reducing aerodynamic drag and noise of circular cylinders with non-uniform porous coatings

2020 ◽  
Vol 107 ◽  
pp. 106308
Author(s):  
Pikai Zhang ◽  
Yu Liu ◽  
Zhiyong Li ◽  
Hanru Liu ◽  
Yannian Yang
Keyword(s):  
Aerodynamic Drag ◽  
Numerical Study ◽  
Circular Cylinders ◽  
Porous Coatings
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