Analytical solutions of heat transfer for laminar flow in rectangular channels

Rybiński, Witold; Mikielewicz, Jarosław

doi:10.2478/aoter-2014-0031

Cited by 17 publications

(6 citation statements)

References 4 publications

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“…For a quantitative comparison between the measured and the calculated flow velocities, an analytical solution for the velocity profile was determined. 44 Velocity measurements were recovered using all three models and the two ensemble versions and were compared to analytical calculations by determining mean relative deviations. The ranking of the models differs compared to the training dataset.…”

Section: Flow Measurementsmentioning

confidence: 99%

Calibration of astigmatic particle tracking velocimetry based on generalized Gaussian feature extraction

Franchini

Charogiannis

Markides

et al. 2019

Advances in Water Resources

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Flow and transport in porous media are driven by pore scale processes. Particle tracking in transparent porous media allows for the observation of these processes at the time scale of ms. We demonstrate an application of defocusing particle tracking using brightfield illumination and a CMOS camera sensor. The resulting images have relatively high noise levels. To address this challenge, we propose a new calibration for locating particles in the out-of-plane direction. The methodology relies on extracting features of particle images by fitting generalized Gaussian distributions to particle images. The resulting fitting parameters are then linked to the out-of-plane coordinates of particles using flexible machine learning tools. A workflow is presented which shows how to generate a training dataset of fitting parameters paired to known out-of-plane locations. Several regression models are tested on the resulting training dataset, of which a boosted regression tree ensemble produced the lowest cross-validation error. The efficiacy of the proposed methodology is then examined in a laminar channel flow in a large measurement volume of 2048, 1152 and 3000 μm in length, width and depth respectively. The size of the test domain reflects the representative elementary volume of many fluid flow phenomena in porous media. Such large measurement depths require the collection of images at different focal levels. We acquired images at 21 focal levels 150 μm apart from each other. The error in predicting the out-of-plane location in a single slice of 240 μm thickness was found to be 7 μm, while in-plane locations were determined with sub-pixel resolution (below 0.8 μm). The mean relative error in the velocity measurement was obtained by comparing the experimental results to an analytic model of the flow. The estimated displacement errors in the axial direction of the flow were 0.21 pixel and 0.22 pixel at flows rates of 1.0 mL/h and 2.5 mL/h, respectively. These results demonstrate that it is possible to conduct three-dimensional particle tracking in a representative elementary volume based on a simple apparatus comprising a microscope with standard brightfield illumination and a camera with CMOS sensor.

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Section: Flow Measurementsmentioning

confidence: 99%

Calibration of astigmatic particle tracking velocimetry based on generalized Gaussian feature extraction

Franchini

Charogiannis

Markides

et al. 2019

Advances in Water Resources

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“…6 a). The flow is laminar 40 since the Reynolds number is small (of order 10 −5 ). The fluid exiting the pore through the orifice is a jet submerged in the fluid of the ACH channel, and the shape of that jet is a cone centred on the pore axis according to Hinze theory 41 .…”

Section: Methodsmentioning

confidence: 99%

Real time observation of the interaction between aluminium salts and sweat under microfluidic conditions

Sakhawoth

Dupire

Léonforte

et al. 2021

Sci Rep

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Aluminium salts such as aluminium chlorohydrate (ACH) are the active ingredients of antiperspirant products. Their mechanism of action involves a temporary and superficial plugging of eccrine sweat pores at the skin surface. We developed a microfluidic system that allows the real time observation of the interactions between sweat and ACH in conditions mimicking physiological sweat flow and pore dimensions. Using artificial sweat containing bovine serum albumin as a model protein, we performed experiments under flowing conditions to demonstrate that pore clogging results from the aggregation of proteins by aluminium polycations at specific location in the sweat pore. Combining microfluidic experiments, confocal microscopy and numerical models helps to better understand the physical chemistry and mechanisms involved in pore plugging. The results show that plugging starts from the walls of sweat pores before expanding into the centre of the channel. The simulations aid in explaining the influence of ACH concentration as well as the impact of flow conditions on the localization of the plug. Altogether, these results outline the potential of both microfluidic confocal observations and numerical simulations at the single sweat pore level to understand why aluminium polycations are so efficient for sweat channel plugging.

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“…with h and w as the channel height and width, the pressure gradient in the flow direction, η the fluid dynamic viscosity, the cross-section aspect ratio and s n =(2 n −1) π ([ 16 ], eq. (19)).…”

Section: Methodsmentioning

confidence: 99%

Flow-dependent fluorescence of CCVJ

2017

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BackgroundThe molecular rotor 9-(2-Carboxy-2-cyanovinyl)julolidine (CCVJ) is presumed to have a sensitivity towards velocity or shear which is supposed to result in a change in fluorescence quantum yield. Furthermore, a previously reported photoisomeric behavior may contribute to the measured fluorescence intensity changes. The goal of this research was to examine the hypothesized behavior theoretically and experimentally from the perspective of fluid dynamics.ResultsA correlation between stirring rate and intensity could not be established in the present experiments with a completely illuminated sample in contrast to previously reported experiments in spectrofluorometers. Experiments and theoretical models of a Poiseuille flow were in good agreement with the photoisomeric behavior but excluded the influence of shear. Further experiments in a flow chamber supported the photoisomery hypothesis as well.ConclusionNo experimental evidence for the influence of velocity on the fluorescence intensity of CCVJ was found. The hypothesis of shear sensitivity was excluded as well. The results are consistent with the photoisomeric behavior of CCVJ.

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Analytical solutions of heat transfer for laminar flow in rectangular channels

Cited by 17 publications

References 4 publications

Calibration of astigmatic particle tracking velocimetry based on generalized Gaussian feature extraction

Calibration of astigmatic particle tracking velocimetry based on generalized Gaussian feature extraction

Real time observation of the interaction between aluminium salts and sweat under microfluidic conditions

Flow-dependent fluorescence of CCVJ

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