Abstract
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.
Highlights
The flow over bluff bodies has been continuously studied for decades, due to its numerous applications, such as flow around aircraft, automobiles, bridges and high-rise buildings [1]
They have been identified as an effective means for the control of aerodynamic noise and vibration from bluff bodies, blunt edges and aerofoils with the general consensus being that they lead to the stabilisation of turbulence, vortex shedding attenuation, control of flow instabilities and reduction in noise [8]
The primary goal of this research was the development of a numerical model to investigate various configurations of a leeward porous coating on a cylinder in cross-flow
Summary
The flow over bluff bodies has been continuously studied for decades, due to its numerous applications, such as flow around aircraft, automobiles, bridges and high-rise buildings [1]. Porous coatings are a passive flow control method that have received significant attention, primarily for their ability to reduce aerodynamic noise [2] They have shown potential with regard to drag reduction. The use of porous treatments has been investigated for decades, with flow over river beds [4], bluff bodies [2], aerofoils [5], porous screens [6] and forest canopies [7], among the areas being studied When it comes to flow around bluff bodies, one of the main focuses is the control of vortex shedding, as this phenomenon can result in structural vibration, acoustic noise, increased drag, stresses on structures etc. They have been identified as an effective means for the control of aerodynamic noise and vibration from bluff bodies, blunt edges and aerofoils with the general consensus being that they lead to the stabilisation of turbulence, vortex shedding attenuation, control of flow instabilities and reduction in noise [8]
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