3D Printed Structured Porous Treatments for Flow Control around a Circular Cylinder

Abstract

The use of porous coatings is one of the passive flow control methods used to reduce turbulence, noise and vibrations generated due to fluid flow. Porous coatings for flow stabilization have potential for a light-weight, cost-effective, and customizable solution. The design and performance of a structured porous coating depend on multiple control parameters like lattice size, strut thickness, lattice structure/geometry, etc. This study investigated the suitability of MSLA 3D printers to manufacture porous coatings based on unit cell designs to optimize porous lattices for flow control behind a cylinder. The Reynolds number used was 6.1×104–1.5×105 and the flow measurements were taken using a hotwire probe. Different experiment sets were conducted for single cylinder with varying control parameters to achieve best performing lattice designs. It was found that lattice structures with higher porosity produced lower turbulence intensity in the wake of the cylinder. However, for constant porosity lattice structures, there was negligible difference in turbulence and mean wake velocity levels. Coating thickness did not have a linear relationship with turbulence reduction, suggesting an optimal thickness value. For constant porosity coatings, cell count in coating thickness did not influence the turbulence or mean wake velocity. Partial coating designs like helical and spaced coatings had comparable performance to that of a full coating. MSLA printers were found capable of manufacturing thin and complex porous lattices.

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

“…The first point of note is the considerable increase in simulation time required, as the time to quasi-steady-state vortex shedding increased by approximately 350% when compared to the smooth case. This is in agreement with both the experimental and numerical literature, all of which found there was a significant delay in shear layer roll up and, thus, vortex shedding [2,[9][10][11][12][13][14][15][16][17][18][19][23][24][25]. Naito et al [14,15] attribute this to the stabilisation of the shear layer as a result of low-energy fluid being injected downstream of the porous layer.…”

“…Bathla and Kennedy [23] investigated the use of 3D-printed porous coatings implemented partially along the span of a cylinder. They concluded that the full porous coatings reduced wake width and turbulence intensity and found that the partial coatings had the potential to provide the same or better turbulence reductions.…”

Combined Passive/Active Flow Control of Drag and Lift Forces on a Cylinder in Crossflow Using a Synthetic Jet Actuator and Porous Coatings

“…This agrees with Sueki et al [29], who showed experimentally that a full porous coating for 4.6 × 10 4 < Re < 8.3 × 10 4 reduces aerodynamic noise and increases the size of the zero velocity region in the cylinder wake, attributing this to the porous coating reducing fluid momentum in the wake and subduing vortex shedding. Bathla and Kennedy [12] showed experimentally that high porosity coatings significantly reduced turbulence in the wake, with a 95% porosity coating offering a 70% reduction in turbulence compared to a smooth cylinder. Hu et al [30] found numerically that partial porous coatings around the separation point can reduce drag by 30% .…”

“…Each has been studied previously in isolation, with numerous studies demonstrating drag reduction using SJAs [4][5][6][7] and porous coatings [8][9][10] when applied to cylinders in crossflow. Porous coatings around cylinders have also been shown to largely suppress oscillating lift forces [11] and reduce noise [12]. Therefore this current study focuses on altering the drag coefficient (C d ) and the root-mean-square (RMS) lift coefficient (C l(rms) ) of a cylinder using these technologies.…”

Scalable3D‐printed lattices for pressure control in fluid applications

“…Unlike their stochastic counterparts, lattices can be designed with defined dimensions in an ordered arrangement. However, while additively manufactured lattices and periodic structures have been explored in detail for their mechanical and thermal properties, their use in fluid applications remains a high‐potential area 16–22 . Much of the recent investigation into lattices for fluid applications have emerged from studies of open‐cell foams.…”