Hydrodynamic cavitation in microfluidic devices with roughened surfaces

Abstract

The importance of the hydrodynamic cavitation phenomenon in small domains has been increasing during recent decades along with the global demand for microfluidic devices involving small-scale cavitation applications. Different characteristics of microscale hydrodynamic cavitation relative to the conventional size can be exploited in futuristic applications and improvements in the performances of new-generation microfluidic devices. Therefore, in-depth studies on the fundamentals of microscale hydrodynamic cavitation are required to reveal new physics of small-scale hydrodynamic cavitation. In this study, microfluidic devices with rough surfaces and micro restrictive elements are fabricated so that a basic study on ‘Hydrodynamic Cavitation on Chip’ is performed. Cavitating flows are investigated under transient and fully developed turbulent conditions within the Reynolds number range between 2962 and 8620 and cavitation number range between 2.025 and 0.72. The microfluidic devices have short restrictive elements with hydraulic diameters of 75, 66.6 and 50 µm and lengths of 2 mm, which are connected to a bigger microchannel with a width of 900 µm and length of 2 mm, called an ‘extended channel’. Different upstream pressures up to 900 Psi are applied at the inlet. The hydrodynamic cavitation inception is recorded and analyzed for each microfluidic device. Flow patterns are characterized inside the microfluidic devices from cavitation inception to chocked flow conditions. Accordingly, it is observed that the transition from inception to choked occurs slowly in contrast to microscale hydrodynamic cavitation results in the literature under laminar flow conditions. Moreover, the comparison between microfluidic devices with roughened and plane (smooth) surfaces reveals that the roughened surface results in more intense cavitating flows, especially at higher upstream pressures relative to the plane surface.

An Experimental Investigation of Coherent Structures and Induced Noise Characteristics of the Partial Cavitating Flow on a Two-Dimensional Hydrofoil

“…He also pointed out different cavitation behaviors attributed to system instabilities, difference in gas content, and surface roughness of the foil. The physical mechanism of the cavity inception is quite complex and somewhat different on scale models and full scale of submerged objects [2][3][4], and also in microsystems [5][6][7][8]. Research has identified the critical velocity for which a sudden change in the desinent cavitation number occurs as an effect of a passing from long to short laminar separation bubbles [9].…”

Cavitating Flow through a Micro-Orifice

“…Since cavitation may reduce efficiency, generate vibration and acoustic noise, or even cause a catastrophic disaster [12,13], the hydraulic cavitation inside macro machinery has attracted enormous attention from researchers [13,14,15]. Although there are experimental and numerical investigations demonstrating that a microfluidic system with micro-orifices may suffer from the influences of cavitation, there are only a few that concentrate on cavitation inside a microfluidic system until now [16,17,18,19,20,21]. Investigations have mostly focused on explaining the cavitation phenomenon, the effects of turbulent state, and the structural parameters of cavitation characteristics.…”

“…Investigations have mostly focused on explaining the cavitation phenomenon, the effects of turbulent state, and the structural parameters of cavitation characteristics. The principals obtained from macroscale studies may still be applied to a microscale structure [17,18,19,20,21,22,23,24,25,26,27,28,29], however, the turbulent state and scale can affect cavitation characteristics [20].…”

Engineered Lateral Roughness Element Implementation and Working Fluid Alteration to Intensify Hydrodynamic Cavitating Flows on a Chip for Energy Harvesting

“…Their results showed that the roughness on the channel surface led to intensified cavitating flows in comparison with a smooth channel over the same range of flow rate. They also suggested that longer microchannels were suitable for energy harvesting applications because of the penetration of the emerging twin cavities [19]. It should be noted that the entire downstream region of microchannel could be filled with vapor and large vapor bubbles by causing twin cavities, which could be exploited in energy harvesting.…”