Visualization of microscale cavitating flow regimes via particle shadow sizing imaging and vision based estimation of the cone angle

Deprem

et al. 2019

Sci Rep

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The importance of surface topology for the generation of cavitating flows in micro scale has been emphasized during the last decade. In this regard, the utilization of surface roughness elements is not only beneficial in promoting mass transportation mechanisms, but also in improving the surface characteristics by offering new interacting surface areas. Therefore, it is possible to increase the performance of microfluidic systems involving multiphase flows via modifying the surface. In this study, we aim to enhance generation and intensification of cavitating flows inside microfluidic devices by developing artificial roughness elements and trapping hydrophobic fluorinated lubricants. For this, we employed different microfluidic devices with various hydraulic diameters, while roughness structures with different lengths were formed on the side walls of microchannel configurations. The surface roughness of these devices was developed by assembling various sizes of silica nanoparticles using the layer-by-layer technique (D2). In addition, to compare the cavitating flow intensity with regular devices having plain surfaces (D1), highly fluorinated oil was trapped within the pores of the existing thin films in the configuration D2 via providing the Slippery Liquid-Infused Porous Surface (D3). The microfluidic devices housing the short microchannel and the extended channel were exposed to upstream pressures varying from 1 to 7.23 MPa. Cavitation inception and supercavitation condition occured at much lower upstream pressures for the configurations of D2 and D3. Interestingly, hydraulic flip, which rarely appears in the conventional conical nozzles at high pressures, was observed at moderate upstream pressures for the configuration D2 proving the air passage existence along one side of the channel wall.

Section: Methodsmentioning

confidence: 99%

A New Method for Intense Cavitation Bubble Generation on Layer-by-Layer Assembled SLIPS

Aghdam

Deprem

et al. 2019

Sci Rep

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“…All the microfluidic devices were fabricated out of double side polished silicon wafers with a thickness of 380 µm. A schematic of the fabrication protocol [16] is shown in Figure 1A. All the devices employed in this study have small and short side wall roughness elements, as reported in detail in the previous studies of the authors [14].…”

Section: Fabrication Of the Microfluidics Devicementioning

confidence: 95%

“…Cavitating flows generated in the microchannel were visualized at different regions in the microfluidic devices. The whole steps of the visualization experiments were explained in detail in the previous study of the authors [16].…”

Section: Cavitation Experimentsmentioning

confidence: 99%

Facile hydrodynamic cavitation ON CHIP via cellulose nanofibers stabilized perfluorodroplets inside layer-by-layer assembled SLIPS surfaces

Chemical Engineering Journal

Aghdam

Gevari

et al. 2020

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“…Different mechanical phenomena such as inception, developed cavities and supercavitation at the outlet of the microchannel are recorded by the high-speed visualization camera. The snaps of the cavitating flows are gathered by a double-shutter high-speed complementary metal-oxide semiconductor (CMOS) camera, which allows two successive frames to be visualized with a resolution of 1280 x 800 pixels (0.02 mm pixel size) within a short time delay [24][25][26]. A macro camera lens is mounted on the CMOS camera (type K2 DistaMax with focal length: s = 50 mm and f-number: f = 1.2) at a distance of 342 mm from the imaging plane, yielding a magnification of M = 0.137.…”

Section: B Experimental Setup and Proceduresmentioning

confidence: 99%

The Hydrodynamic Cavitation Manifestation in Small Chips

2021

IEEE Access

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Cavitation is a phase change phenomenon created by the static pressure reduction of a liquid medium at a constant temperature. This process has been considered as a disadvantageous mechanism in most turbomachinery systems, however, its potential in releasing energy at the bubble collapse stage has received lots of attention in recent decades. Particularly, the applicability of this phenomenon in micro scale gives rise to the research studies in different fields, i.e., wastewater treatment and medical imaging. In this study, microfluidic devices housing small microchannels have been fabricated to study the generation of the cavitating flow patterns bubbles. The main focuses in this work are on the surface and side wall roughness together with the size reduction effects on cavitation bubble generation. Accordingly, the microfluidic devices were fabricated using the techniques adopted from semiconductor based micro-fabrication. The experiments were performed at relatively higher upstream pressure, 4 to 7 MPa, to investigate the durability of the devices and flow patterns features. The results show that the side wall roughness elements are very effective in the small microchannels in terms of facile cavitating flow generation, while the size reduction in the diameter of the channel does not accompany intensified cavitating flow necessarily.