Experimental Investigation of Thermocapillary Convection Near an Evaporating Meniscus

Author(s):  
H. K. Dhavaleswarapu ◽  
P. Chamarthy ◽  
S. V. Garimella ◽  
J. Y. Murthy ◽  
S. T. Wereley

Experimental visualizations of the 3D convection patterns generated near an evaporating meniscus in a capillary tube are presented. Epi-fluorescent micro-particle image velocimetry (μPIV) using a two-cavity frequency doubled ND-YAG laser as the illumination source is employed to map the small-scale spatial flow fields near the meniscus. Methanol seeded with 0.5 μm polystyrene fluorescent particles is used as the experimental fluid. These fluorescent particles absorb light from the laser beam (λabs~542 nm, green) and emit a longer wavelength light ((λem~612 nm, red). Images obtained at a specified time delay (~20 ms) were interrogated to obtain vector flow fields.

Volume 4 ◽  
2004 ◽  
Author(s):  
Dong Liu ◽  
Suresh V. Garimella ◽  
Steve T. Wereley

A non-intrusive diagnostic technique, infrared micro-particle image velocimetry (IR-PIV), is developed for measuring flow fields within MEMS devices with micron-scale resolution. This technique capitalizes on the transparency of silicon in the infrared region, and overcomes the limitation posed by the lack of optical access with visible light to sub-surface flow in silicon-based micro-structures. Experiments with laminar flow of water in a circular micro-capillary tube of hydraulic diameter 255 μm demonstrate the efficacy of this technique. The experimental measurements agree very well with velocity profiles predicted from laminar theory. Cross-correlation and auto-correlation algorithms are employed to measure very-low and moderate-to-high velocities, respectively; the former approach is suitable for biomedical applications while the latter would be needed for measurements in electronics cooling. The results indicate that the IR-PIV technique effectively extends the application of regular micro-PIV techniques, and has great potential for flow measurements in silicon-based microdevices.


2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung

Flow structures and pressure drops were investigated in rectangular serpentine micro-channels with miter bends which had hydraulic diameters of 0.209mm, 0.395mm and 0.549mm respectively. To evaluate the bend effect, the additional pressure drop due to the miter bend must be obtained. Three groups of micro-channels were fabricated to remove the inlet and outlet losses. A validated micro-particle image velocimetry (μPIV) system was used to achieve the flow structure in a serpentine micro-channel with hydraulic diameter of 0.173mm. The experimental results show the vortices around the outer and inner walls of the bend do not form when Re<100. Those vortices appear and continue to develop with the Re number when Re> 100-300, and the shape and size of the vortices almost remain constant when Re>1000. The bend loss coefficient Kb was observed to be related with the Re number when Re<100, with the Re number and channel size when Re>100. It almost keeps constant and changes in the range of ± 10% When Re is larger than some value in 1300-1500. And a size effect on Kb was also observed.


2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Petter Ekman ◽  
James Venning ◽  
Torbjörn Virdung ◽  
Matts Karlsson

Abstract The Ahmed body is one of the most well-investigated vehicle bodies for aerodynamic purposes. Despite its simple geometry, the flow around the body, especially at the rear, is very complex as it is dominated by a large wake with strong interaction between vortical structures. In this study, the flow around the 25 deg Ahmed body has been investigated using large eddy simulations and compared to high-resolution particle image velocimetry (PIV) measurements. Special emphasis was put on studying three commonly used sub-grid scale (SGS) models and their ability to capture vortical structures around the Ahmed body. The ability of the SGS models to capture the near-wall behavior and small-scale dissipation is crucial for capturing the correct flow field. Very good agreement between simulations and PIV measurements were seen when using the dynamic Smagorinsky-Lilly and the wall-adopting local eddy-viscosity SGS models, respectively. However, the standard Smagorinsky-Lilly model was not able to capture the flow patterns when compared to the PIV measurements due to shortcomings in the near-wall modeling in the standard Smagorinsky-Lilly model, resulting in overpredicted separation.


2004 ◽  
Vol 126 (5) ◽  
pp. 585-593 ◽  
Author(s):  
Pramote Hochareon ◽  
Keefe B. Manning ◽  
Arnold A. Fontaine ◽  
John M. Tarbell ◽  
Steven Deutsch

In order to bridge the gap of existing artificial heart technology to the diverse needs of the patient population, we have been investigating the viability of a scaled-down design of the current 70 cc Penn State artificial heart. The issues of clot formation and hemolysis may become magnified within a 50 cc chamber compared to the existing 70 cc one. Particle image velocimetry (PIV) was employed to map the entire 50 cc Penn State artificial heart chamber. Flow fields constructed from PIV data indicate a rotational flow pattern that provides washout during diastole. In addition, shear rate maps were constructed for the inner walls of the heart chamber. The lateral walls of the mitral and aortic ports experience high shear rates while the upper and bottom walls undergo low shear rates, with sufficiently long exposure times to potentially induce platelet activation or thrombus formation. In this study, we have demonstrated that PIV may adequately map the flow fields accurately in a reasonable amount of time. Therefore, the potential exists of employing PIV as a design tool.


Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3090 ◽  
Author(s):  
Fahrettin Ergin ◽  
Bo Watz ◽  
Nicolai Gade-Nielsen

Image-based sensor systems are quite popular in micro-scale flow investigations due to their flexibility and scalability. The aim of this manuscript is to provide an overview of current technical possibilities for Particle Image Velocimetry (PIV) systems and related image processing tools used in microfluidics applications. In general, the PIV systems and related image processing tools can be used in a myriad of applications, including (but not limited to): Mixing of chemicals, droplet formation, drug delivery, cell counting, cell sorting, cell locomotion, object detection, and object tracking. The intention is to provide some application examples to demonstrate the use of image processing solutions to overcome certain challenges encountered in microfluidics. These solutions are often in the form of image pre- and post-processing techniques, and how to use these will be described briefly in order to extract the relevant information from the raw images. In particular, three main application areas are covered: Micro mixing, droplet formation, and flow around microscopic objects. For each application, a flow field investigation is performed using Micro-Particle Image Velocimetry (µPIV). Both two-component (2C) and three-component (3C) µPIV systems are used to generate the reported results, and a brief description of these systems are included. The results include detailed velocity, concentration and interface measurements for micromixers, phase-separated velocity measurements for the micro-droplet generator, and time-resolved (TR) position, velocity and flow fields around swimming objects. Recommendations on, which technique is more suitable in a given situation are also provided.


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