scholarly journals Air-Bubble Induced Mixing: A Fluidic Mixer Chip

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 195 ◽  
Author(s):  
Xiaoyu Jia ◽  
Bingchen Che ◽  
Guangyin Jing ◽  
Ce Zhang
Keyword(s):  
Bulk Solution ◽  
Liquid Volume ◽  
Mixing Efficiency ◽  
Flow Profile ◽  
Air Bubbles ◽  
Complex Flow ◽  
Air Bubble ◽  
Potential Applications ◽  
Unique Approach ◽  
Medical Analysis

In this study, we report the design and fabrication of a novel fluidic mixer. As proof-of-concept, the laminar flow in the main channel is firstly filled with small air-bubbles, which act as active stirrers inducing chaotic convective turbulent flow, and thus enhance the solutes mixing even at a low input flow rate. To further increase mixing efficiency, a design of neck constriction is included, which changes the relative positions of the inclusion bubbles significantly. The redistribution of liquid volume among bubbles then causes complex flow profile, which further enhances mixing. This work demonstrates a unique approach of utilizing air bubbles to facilitate mixing in bulk solution, which can find the potential applications in microfluidics, fast medical analysis, and biochemical synthesis.

scholarly journals Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 637 ◽  
Author(s):  
Mahmut Burak Okuducu ◽  
Mustafa M. Aral
Keyword(s):  
Fluid Flow ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Flow Profile ◽  
Complex Flow ◽  
Mixing Index ◽  
Micro Channels ◽  
Mixing Dynamics ◽  
Passive Micromixer ◽  
Novel Design

Laminar fluid flow and advection-dominant transport produce ineffective mixing conditions in micromixers. In these systems, a desirable fluid mixing over a short distance may be achieved using special geometries in which complex flow paths are generated. In this paper, a novel design, utilizing semi-circular ridges, is proposed to improve mixing in micro channels. Fluid flow and scalar transport are investigated employing Computational Fluid Dynamics (CFD) tool. Mixing dynamics are investigated in detail for alternative designs, injection, and diffusivity conditions. Results indicate that the convex alignment of semi-circular elements yields a specific, helicoidal-shaped fluid flow along the mixing channel which in turn enhances fluid mixing. In all cases examined, homogenous concentration distributions with mixing index values over 80% are obtained. When it is compared to the classical T-shaped micromixer, the novel design increases mixing index and mixing performance values by the factors of 8.7 and 3.3, respectively. It is also shown that different orientations of ridges adversely affect the mixing efficiency by disturbing the formation of helicoidal-shaped flow profile.

scholarly journals Effect of cannulation site on emboli travel during cardiac surgery

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Mira Puthettu ◽  
Stijn Vandenberghe ◽  
Stefanos Demertzis
Keyword(s):  
Cardiac Surgery ◽  
In Vitro Study ◽  
Blood Stream ◽  
Air Bubbles ◽  
Arterial Tree ◽  
Air Bubble ◽  
Cannulation Site ◽  
The Brain

Abstract Background During cardiac surgery, micro-air emboli regularly enter the blood stream and can cause cognitive impairment or stroke. It is not clearly understood whether the most threatening air emboli are generated by the heart-lung machine (HLM) or by the blood-air contact when opening the heart. We performed an in vitro study to assess, for the two sources, air emboli distribution in the arterial tree, especially in the brain region, during cardiac surgery with different cannulation sites. Methods A model of the arterial tree was 3D printed and included in a hydraulic circuit, divided such that flow going to the brain was separated from the rest of the circuit. Air micro-emboli were injected either in the HLM (“ECC Bubbles”) or in the mock left ventricle (“Heart Bubbles”) to simulate the two sources. Emboli distribution was measured with an ultrasonic bubble counter. Five repetitions were performed for each combination of injection site and cannulation site, where air bubble counts and volumes were recorded. Air bubbles were separated in three categories based on size. Results For both injection sites, it was possible to identify statistically significant differences between cannulation sites. For ECC Bubbles, axillary cannulation led to a higher amount of air bubbles in the brain with medium-sized bubbles. For Heart Bubbles, aortic cannulation showed a significantly bigger embolic load in the brain with large bubbles. Conclusions These preliminary in vitro findings showed that air embolic load in the brain may be dependent on the cannulation site, which deserves further in vivo exploration.

An experimental investigation of heat transfer characteristics of water based Al2O3 nanofluid operated shell and tube heat exchanger with air bubble injection technique

2017 ◽  
Vol 6 (4) ◽  
pp. 83 ◽  
Author(s):  
Gaurav Thakur ◽  
Gurpreet Singh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Al2o3 Nanoparticles ◽  
Air Bubbles ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger ◽  
Air Bubble ◽  
Transfer Characteristics ◽  
Water Based ◽  
Shell And Tube

The thermal performance of shell and tube heat exchangers has been enhanced with the use of different techniques. Air bubble injection is one such promising and inexpensive technique that enhances the heat transfer characteristics inside shell and tube heat exchanger by creating turbulence in the flowing fluid. In this paper, experimental study on heat transfer characteristics of shell and tube heat exchanger was done with the injection of air bubbles at the tube inlet and throughout the tube with water based Al2O3 nanofluids i.e. (0.1%v/v and 0.2%v/v). The outcomes obtained for both the concentrations at two distinct injection points were compared with the case when air bubbles were not injected. The outcomes revealed that the heat transfer characteristics enhanced with nanoparticles volumetric concentration and the air bubble injection. The case where air bubbles were injected throughout the tube gave maximum enhancement followed by the cases of injection of air bubbles at the tube inlet and no air bubble injection. Besides this, water based Al2O3 nanofluid with 0.2%v/v of Al2O3 nanoparticles gave more enhancement than Al2O3nanofluid with 0.1%v/v of Al2O3 nanoparticles as the enhancement in the heat transfer characteristics is directly proportional to the volumetric concentration of nanoparticles in the base fluid. The heat transfer rate showed an enhancement of about 25-40% and dimensionless exergy loss showed an enhancement of about 33-43% when air bubbles were injected throughout the tube. Moreover, increment in the heat transfer characteristics was also found due to increase in the temperature of the hot fluid keeping the flow rate of both the heat transfer fluids constant.

scholarly journals Clinical outcomes of management of posterior capsule rupture with air bubble techniques

2020 ◽  
Vol 13 (12) ◽  
pp. 2007-2011
Author(s):  
Jongyeop Park ◽  
Jinhyun Kim
Keyword(s):  
Case Series ◽  
Posterior Capsule ◽  
Air Bubbles ◽  
Retrospective Case ◽  
Air Bubble ◽  
Posterior Capsule Rupture ◽  
New Surgical Technique ◽  
Capsule Rupture ◽  
Ophthalmic Viscosurgical Device

AIM: To introduce a new surgical technique, air-bubble technique for the management of posterior capsule rupture (PCR) and to evaluate the safety and efficacy of the technique. METHODS: A retrospective case series analysis of 24 eyes of 24 patients, in which the air bubble technique was used for the management of PCR, was performed. Once PCR occurred, a dispersive ophthalmic viscosurgical device (OVD) was injected into the tear. And small volumes (0.2-0.3 mL) of air bubbles were injected beneath the OVD. The air bubble served as a physical barrier and supported the posterior capsule. RESULTS: After surgery, none of the patients had serious complications during the follow-up period of 1y. Extension of the PCR size occurred in only 2 cases, and additional OVD injection was required only in 3 cases. Air bubbles imparted great stability to the nuclear pieces and the posterior capsule. CONCLUSION: The air-bubble technique may be considered a safe and effective procedure for managing a PCR. It may be of value to the inexperienced cataract surgeon.

scholarly journals Simulated features of the air-hydrate formation process in the Antarctic ice sheet at Vostok

1999 ◽  
Vol 29 ◽  
pp. 191-201 ◽  
Author(s):  
Andrey N. Salamatin ◽  
Vladimir Ya. Lipenkov ◽  
Takeo Hondoh ◽  
Tomoko Ikeda
Keyword(s):  
Ice Core ◽  
Hydrate Formation ◽  
Ice Cores ◽  
Air Bubbles ◽  
Air Bubble ◽  
Self Diffusion ◽  
Rate Limiting Step ◽  
Typical Time ◽  
Polar Ice Sheets ◽  
Selective Diffusion

AbstractA recently developed theory of post-nucleation conversion of an air bubble to air-hydrate crystal in ice is applied to simulate two different types of air-hydrate formation in polar ice sheets. The work is focused on interpretation of the Vostok (Antarctica) ice-core data. The hydrostatic compression of bubbles is the rate-limiting step of the phase transformation which is additionally influenced by selective diffusion of the gas components from neighboring air bubbles. The latter process leads to the gas fractionation resulting in lower (higher) N2/O2 ratios in air hydrates (coexisting bubbles) with respect to atmospheric air. The typical time of the post-nucleation conversion decreases at Vostok from 1300-200 a at the beginning to 50-3 a at the end of the transition zone. The model of the diffusive transport of the air constituents from air bubbles to hydrate crystals is constrained by the data of Raman spectra measurements. The oxygen and nitrogen self-diffusion (permeation) coefficients in ice are determined at 220 K as 4.5 × 10−8 and 9.5 × 10−8 mm2 a−1, respectively while the activation energy is estimated to be about 50 kJ mol−1. The gas-fractionation time-scale at Vostok, τF ∼300 a, appears to be two orders of magnitude less than the typical time of the air-hydrate nucleation, τz ∼30-35 ka, and thus the condition for the extreme gas fractionation, τF ≪ τz is satisfied. Application of the theory to the GRIP and GISP2 ice cores shows that on average, a significant gas fractionation cannot be expected for air hydrates in central Greenland. However, a noticeable (statistically valid) nitrogen enrichment might be observed in the last air bubbles at the end of the transition.

scholarly journals Multiple air-bubble enhanced oil rupture on nanostructured cellulose fabric for easy-oil cleaning fouled in a dry state

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Min-Sung Kim ◽  
Tae-Jun Ko ◽  
Seong Jin Kim ◽  
Young-A. Lee ◽  
Kyu Hwan Oh ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Solid Fraction ◽  
High Aspect Ratio ◽  
Air Bubbles ◽  
Oil Droplets ◽  
Water Contact ◽  
Air Bubble ◽  
Cellulose Fabric ◽  
Oily Water ◽  
Oil Fouling

Abstract Nanostructured cellulose fabric with an air-bubble-enhanced anti-oil fouling property is introduced for quick oil-cleaning by water even with the surface fouled by oil before water contact under a dry state. It is very challenging to recover the super-hydrophilicity because once the surface is oil-fouled, it is hard to be re-wetted by water. Anti-oil-fouling under a dry state was realized through two main features of the nanostructured, porous fabric: a low solid fraction with high-aspect-ratio nanostructures significantly increasing the retracting forces, and trapped multiscale air bubbles increasing the buoyancy and backpressure for an oil-layer rupture. The nanostructures were formed on cellulose-based rayon microfibers through selective etching with oxygen plasma, forming a nanoscale open-pore structure. Viscous crude oil fouled on a fabric under a dry state was cleaned by immersion into water owing to a higher water affinity of the rayon material and low solid fraction of the high-aspect-ratio nanostructures. Air bubbles trapped in dry porous fibers and nanostructures promote oil detachment from the fouled sites. The macroscale bubbles add buoyancy on top of the oil droplets, enhancing the oil receding at the oil-water-solid interface, whereas the relatively smaller microscale bubbles induce a backpressure underneath the oil droplets. The oil-proofing fabric was used for protecting underwater conductive sensors, allowing a robot fish to swim freely in oily water.

Behavior of Micron-Sized Air Bubble in Operating FDBs by Using the Discrete Phase Modeling Method

2013 ◽  
Author(s):  
Y. H. Jung ◽  
G. H. Jang ◽  
K. M. Jung ◽  
C. H. Kang ◽  
H. H. Shin
Keyword(s):  
Fluid Dynamic ◽  
Disk Drive ◽  
Spindle Motor ◽  
Air Bubbles ◽  
Air Bubble ◽  
Discrete Phase Modeling ◽  
Discrete Phase ◽  
The Stability ◽  
Stiffness And Damping ◽  
Oil Injection

Fluid dynamic bearings (FDBs) have been applied to the spindle motor of a computer hard disk drive (HDD) because FDBs provide better dynamical characteristics of lower vibration and noise than ball bearings. However, one of the weaknesses of FBDs is the instability arising from the air bubble in oil lubricant of FDBs. Air bubbles are formed and trapped in oil lubricant by the inappropriate process of oil injection or the external shock. Trapped air bubbles decrease the rotational accuracy and the stability of a rotor-bearing system in such a way to generate non-repeatable run-out (NRRO) and to decrease the stiffness and damping coefficients of FDBs. It is important to predict the path of air bubbles in oil lubricant and to design FDBs in such a way to easily expel air bubbles out of operating FDBs.

The Significance of air Bubbles in Glacier Ice

1950 ◽  
Vol 1 (08) ◽  
pp. 443-451 ◽  
Author(s):  
Henri Bader
Keyword(s):  
Maximum Depth ◽  
Ice Crystals ◽  
Coarse Grained ◽  
Crystallographic Axis ◽  
Air Bubbles ◽  
Very Old ◽  
Air Bubble ◽  
Glacier Ice

Abstract The study of air bubbles in glacier ice can give valuable information on the evolution of the ice. An analysis of the relation between an air bubble and the water associated with it shows that it may be possible to determine the maximum depth from which the ice containing the bubble has emerged. The shapes of the cavities containing water and air bubbles are described. They are found to reflect the anisotropism of ice crystals and reveal that the main crystallographic axis is polar. The question of the mechanism of elimination of air bubbles from glacier ice is raised. The investigations were made on the very old and coarse-grained ice from the foot of the Malaspina Piedmont Glacier in Alaska, which is a temperate glacier.

Fluid Drag Force Production and Motion Control of an Aquarobot Manipulator by Ejecting Air Bubbles

1990 ◽  
Vol 2 (5) ◽  
pp. 351-357
Author(s):  
Masakazu Ogasawara ◽  
◽  
Fumio Hara ◽  
Keyword(s):  
Drag Force ◽  
High Speed ◽  
Robot Manipulator ◽  
Force Production ◽  
Air Bubbles ◽  
Air Bubble ◽  
Fluid Forces ◽  
Fluid Drag ◽  
Force Reduction ◽  
Controlled Flow

The motion of a robot manipulator submerged in water is strongly affected by fluid forces, and it is an important technique to avoid their influence on the motion of an aquarobot manipulator to achieve high-speed, precise motion. This paper deals with extension of the technique of air bubble ejection from the manipulator surface, i.e., the mechanisms of reduction of drag force by air bubble ejection and its effects on the control of the aquarobot manipulator. Using a two-degree-of-freedom and two-joint manipulator, experiments were performed and the following major results were obtained: (1) There exists a particular pattern of air bubble ejection for reduction fluid drag force acting on the manipulator and it resulted in reduction of drag force by 25% compared to that for no air bubble ejection. (2) There exists a particular pattern of air bubble ejection that brought a 40% reduction of the control torque required for compensating the fluid drag force. (3) The major mechanisms for drag force reduction were found to be the controlled flow pattern around the manipulator formed by ejecting air bubbles. However, it is noted that these effects of air bubble ejection were dependent on the mode of manipulator motion.

A Theoretical Study on Air Bubble Motion in a Centrifugal Pump Impeller

1980 ◽  
Vol 102 (4) ◽  
pp. 446-453 ◽  
Author(s):  
Kiyoshi Minemura ◽  
Mitsukiyo Murakami
Keyword(s):  
Centrifugal Pump ◽  
Equations Of Motion ◽  
Bubble Diameter ◽  
Inertia Force ◽  
Air Bubbles ◽  
Bubble Motion ◽  
Pump Impeller ◽  
Air Bubble ◽  
Surrounding Liquid ◽  
Centrifugal Pump Impeller

Equations of motion for air bubbles in a centrifugal pump impeller were obtained and solved numerically for a flow in a radial-flow-type impeller, and the results were compared with experiments. Governing factors for the bubble motion are the force due to the pressure gradient, the drag force due to the flow resistance of the surrounding liquid, and the inertia force due to virtual mass of the liquid. If the bubble diameter is reduced continuously, the effect of the inertia force is also reduced and trajectories of the air bubbles approach more and more to the path of the flowing water.

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