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%.

Bluff Body Drag Reduction Using Passive Flow Control of Jet Boat Tail

2015 ◽  
Vol 8 (2) ◽  
pp. 713-721 ◽  
Author(s):  
Trevor Hirst ◽  
Chuanpeng Li ◽  
Yunchao Yang ◽  
Eric Brands ◽  
Gecheng Zha
Keyword(s):  
Drag Reduction ◽  
Flow Control ◽  
Bluff Body ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Body Drag

Large eddy simulation of base drag reduction using jet boat tail passive flow control

2020 ◽  
Vol 198 ◽  
pp. 104398 ◽  
Author(s):  
Yunchao Yang ◽  
William Bradford Bartow ◽  
Gecheng Zha ◽  
Heyong Xu ◽  
Jianlei Wang
Keyword(s):  
Large Eddy Simulation ◽  
Drag Reduction ◽  
Flow Control ◽  
Passive Flow Control ◽  
Eddy Simulation ◽  
Passive Flow ◽  
Large Eddy ◽  
Base Drag

Investigation of a Passive Flow Control Device in an S-Duct Inlet of a Propulsion System With High Subsonic Flow

2018 ◽  
Author(s):  
Asad Asghar ◽  
Satpreet Sidhu ◽  
William D. E. Allan ◽  
Grant Ingram ◽  
Tom M. Hickling ◽  
...  
Keyword(s):  
Flow Control ◽  
Complex Geometry ◽  
Control Device ◽  
Pressure Recovery ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Flow Control Device ◽  
Inner Radius ◽  
Selection Of ◽  
Numerical Approaches

S-Ducts have wide application on air vehicles with embedded engines. The complex geometry is known to lead to separation downstream of curved profiles. This paper reports the influences on that flow of passive flow control geometries. In these experiments, stream-wise tubercles were applied in an effort to improve the internal performance of S-duct diffusers, parameters including pressure recovery, distortion and swirl. The test articles were tested with the high subsonic (Ma = 0.8) flow and were manufactured using 3D printing. Stream-wise static pressure and exit-plane total pressure were measured in a test rig using surface pressure taps and a 5-probe rotating rake, respectively; the baseline and variant S-ducts were simulated through computational fluid dynamics. The experiments showed that some subtle improvements to the S-Duct distortion could be achieved through careful selection of tubercle geometry. Generally, the recovered flow downstream of the inner radius of the second bend of the S-duct deteriorated, but overall pressure recovery improved. The simulations were useful in characterizing swirl, whereas experiments were not so equipped. Adjustments to the numerical approaches resulted in reasonable agreement with the experiments.

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 Large Eddy Simulation of Base Drag Reduction with Jet Boat-tail Passive Flow Control

2015 ◽  
Vol 126 ◽  
pp. 150-157 ◽  
Author(s):  
Yunchao Yang ◽  
Heyong Xu ◽  
Jianlei Wang ◽  
Gecheng Zha
Keyword(s):  
Large Eddy Simulation ◽  
Drag Reduction ◽  
Flow Control ◽  
Passive Flow Control ◽  
Eddy Simulation ◽  
Passive Flow ◽  
Large Eddy ◽  
Base Drag

Passive Drag Reduction Technology Using Microfiber Coatings

2021 ◽  
Author(s):  
Mitsugu Hasegawa ◽  
Hirotaka Sakaue
Keyword(s):  
Drag Reduction ◽  
Bluff Body ◽  
Separated Flow ◽  
Cylinder Surface ◽  
Cylinder Diameter ◽  
Trailing Edges ◽  
Engineered Surfaces ◽  
Long Fibers ◽  
The Impact ◽  
Influential Parameters

Abstract Engineered surfaces and coatings can passively manipulate flow over a bluff-body without significant retrofitting and are of great technological interest for a broad range of applications in the engineering field. A microfiber coating with a hair-like structure is developed and studied as a passive drag reduction method for flow over a cylinder that features both attached and separated flow. The impact of the microfiber coating on drag is experimentally investigated at a Reynolds number of 6.1 × 104 based on the cylinder diameter. Microfiber coatings of various lengths between 1.1% and 8.0% of the cylinder diameter are fabricated using flocking technology and applied to various positions on the cylinder surface between the leading and trailing edges. It is shown that the microfiber length and location are both influential parameters in drag reduction. Two types of drag reduction can be seen depending on the location of the microfiber coating: (1) Drag is reduced significantly if the microfiber coating is applied before flow separates over the cylinder (2) Drag is reduced moderately if the microfiber coating is applied after the point of flow separation on the cylinder. The former case’s best performance is achieved with a microfiber length of less than 1.8% of the cylinder diameter. The latter case shows better performance with relatively long fibers, where the microfiber’s length is greater than 3.3% of the cylinder diameter.

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