Laminar Flow Conditions Research Articles

Small but Mighty: A Microfluidic Biofuel Cell-Based Biosensor for the Determination of Ethanol

We developed a membraneless-microfluidic biofuel cell (MBFC) for the quantification of ethanol. The system employs anolyte and catholyte solutions, each containing a biocatalyst and redox mediator. The laminar flow conditions in the microfluidic chip minimize the mixing between anolyte and catholyte and obviate the need for a membrane to separate them. When ethanol is added to the anolyte, alcohol dehydrogenase (ADH) catalyzes its oxidation to acetaldehyde, releasing electrons to the anode. On the cathode, electrons are transferred to horseradish peroxidase (HRP), which reduces hydrogen peroxide in the catholyte to water. We optimized key design factors and operating conditions. We also studied the incorporation of glycerol as a viscosity modifier, which improved the power and current density supplied by the MBFC, with a maximum power output of 307 µW cm−2 and an open circuit voltage of 0.733 V. The proposed ethanol/hydrogen peroxide MBFC was successfully applied as a biofuel cell-based sensor for the quantification of ethanol in a commercial liquor.

Numerical analysis of blade height ratio effects on mixing efficiency and energy consumption in triple-blade concentric double-helix static mixers

This work aims to find the optimum value of blade height ratio (R) for improving mixing performance and energy consumption of a Triple-Blade Concentric Double-Helix Static Mixer. In this study, mixing of two fluids at different concentrations subjected to laminar flow conditions is numerically analyzed by using finite element-based Computational Fluid Dynamics simulations. Different values of the R parameter are considered in a wide range of Reynolds numbers (Re = 200–1000). This analysis then carried out an in-depth study of R's effect on mixing performance, strength segregation, mixing index, helicity, velocity profile, pressure drop, pumping power, and efficiency. The findings showed that a blade height ratio of R = 2/3 gave the highest mixing index (MI), with the maximum value of 0.99 at a Re number of 600, which showed the best mixing performance in the channel. Helicity visualization also showed complex helicity patterns with increased vortex interactions for the 2/3 configuration. This geometry gave an improvement in MI by about 17.85% over Triple-Blade Concentric Single-Helix Static Mixer (TB-CSH-SM) with R = 0 at Re = 600. It is also important to mention that increasing the R value leads to an increase in pressure drop and, consequently, an increase in pumping energy consumption. Although R = 2/3 gives the best mixing performance, the energy consumption is relatively higher than that for R = 0, which has the lowest power input but a lower MI. The investigation concludes that R = 2/3 represents a balanced solution since it realizes an optimum mixing performance with a moderate energy consumption and hence is suitable for applications requiring an efficient compromise between mixing quality and energy consumption.

Micro-Assembly Error Control of Specialized MEMS Friction Sensor

A skin friction sensor is a three-dimensional MEMS sensor specially designed for measuring the skin friction of hypersonic vehicle models. The accuracy of skin friction measurement under hypersonic laminar flow conditions is closely related to the fabrication and micro-assembly accuracy of MEMS skin friction sensors. In order to achieve accurate skin friction measurement, high-precision linear laser scanning ranging, multi-axis precision drive, and 3D reconstruction algorithms are investigated; a MEMS skin friction sensor micro-assembly height error measurement system is developed; and the MEMS skin friction sensor micro-assembly height error control method is carried out. The results show that the micro-assembly height error measurement of MEMS skin friction sensors achieves an accuracy of up to 2 μm. The height errors of the MEMS skin friction sensor were controlled within −8 μm to +10 μm after error control. The angular errors were controlled within the range of 0.05–0.25°, significantly improving micro-assembly accuracy in the height direction of the MEMS skin friction sensor. The results of hypersonic wind tunnel tests indicate that the deviation in the accuracy of the MEMS skin friction sensors after applying height error control is about 5%, and the deviation from the theoretical value is 8.51%, which indicates that height error control lays the foundation for improving the accuracy of skin friction measurement under hypersonic conditions.

P0042 Hydrogel-integrated millifluidic system enhances function in primary small intestinal epithelial cells

Abstract Background The intestinal epithelium is protected by a vital mucus layer which is essential for maintaining gut homeostasis and regulating host-microbial interactions. However, studying this mucus layer in vitro has been challenging due to the lack of physiologically relevant models. Methods We hypothesized that culturing human adult intestinal stem cells (ISCs) under flow conditions on a biomimetic scaffold could better recapitulate in vivo epithelial differentiation and mucus production. To test this, we developed a hydrogel-integrated millifluidic chamber, where ISCs were cultured on decellularized and methacrylated porcine small intestinal submucosa (dSIS-MA) under both static and dynamic (laminar flow) conditions. RNA bulk sequencing was used later to explore gene expression profiles across early and late time points to assess the impact of dSIS-MA and fluid flow on ISC differentiation and function over time. Results Our results reveal significant changes in pathways related to epithelial lineage commitment and intestinal barrier function on dSIS-MA compared to tissue culture plastic and in dynamic compared to static conditions, highlighting the critical influence of matrix structure and fluid flow. Conclusion In summary, we have successfully established a model that mimics in vivo conditions and reveals that surface and shear stress strongly impact intestinal epithelial cell development and function. This advanced in vitro approach enhances our understanding of molecular processes underlying epithelial cell behavior in conditions closely resembling the gut environment, with applications in gut health and disease research.

Design and Investigation of a Passive-Type Microfluidics Micromixer Integrated with an Archimedes Screw for Enhanced Mixing Performance.

In recent years, microfluidics has emerged as an interdisciplinary field, receiving significant attention across various biomedical applications. Achieving a noticeable mixing of biofluids and biochemicals at laminar flow conditions is essential in numerous microfluidics systems. In this research work, a new kind of micromixer design integrated with an Archimedes screw is designed and investigated using numerical simulation and experimental approaches. First, the geometrical parameters such as screw length (l), screw pitch (p) and gap (s) are optimized using the Design of Expert (DoE) approach and the Central Composite Design (CCD) method. The experimental designs generated by DoE are then numerically simulated aiming to determine Mixing Index (MI) and Performance Index (PI). For this purpose, COMSOL Multiphysics with two physics modules-laminar and transport diluted species-is used. The results revealed a significant influence of screw length, screw pitch and gap on mixing performance. The optimal design achieved is then scaled up and fabricated using a 3D additive manufacturing technique. In addition, the optimal micromixer design is numerically and experimentally investigated at diverse Reynolds numbers, ranging from 2 to 16. The findings revealed the optimal geometrical parameters that produce the best result compared to other designs are a screw length of 0.5 mm, screw pitch of 0.23409 mm and a 0.004 mm gap. The obtained values of the mixing index and the performance index are 98.47% and 20.15 Pa-1, respectively. In addition, a higher mixing performance is achieved at the lower Reynolds number of 2, while a lower mixing performance is observed at the higher Reynolds number of 16. This study can be very beneficial for understanding the impact of geometrical parameters and their interaction with mixing performance.

Numerical analysis of performance of tube heat exchanger with center-perforated tapered twisted tape

ABSTRACT This paper primarily focuses on the investigation of performance of tube heat exchanger with use of novel center-perforated tapered twisted tape (CPTTT). Due to CPTTT insert provide small wetted area in tube that resulted less friction factor. This less wetted area characteristics of twisted tape insert attract researcher to explore tapered twisted tape insert in combination with tube heat exchanger. The analysis examines the friction factor and thermal performance of a tapered twisted tape insert with a twist ratio (TR) of 2.77, featuring both center circular perforation (diameter 10 mm) and center elliptical perforation (major axis 10 mm, minor axis 5 mm). In addition to this, twin tapered TT configuration is also analyzed; a total of 36 cases are evaluated. A numerical investigation using the ANSYS FLUENT is carried out to analyze the performance of the center-perforated tapered twisted tape with water as working fluid under laminar flow conditions i.e. 500 ≤ Re ≤ 1750. The computational results revealed that the flow resistance is reduced with the proposed twisted tape configuration as compared to the plain twisted tape; however, thermal performance is affected only marginally. In the optimization study, it is advised to use the tapered twisted tape arrangement because it results in a significant reduction of friction factor about 65% as well as the power input for the marginal reduction in thermal performance.

Hydrodynamic Influences on Dissolution Testing Using Flow Channel Apparatuses

AbstractThe extent and rate of solution formation are measured via dissolution testing. Contrary to expectations, the intrinsic dissolution rate (IDR) is not size‐independent, despite normalization of the sample area. By comparing different channel designs and sample diameters, the dimensionless boundary layer normalization factor (BNF) was developed to account for the size‐dependence discovered. With the derived velocity of the boundary (vb), the comparability of dissolution data generated with flow channel apparatuses was established, depending on the flow pattern under laminar flow conditions.

Crystal growth of calcium oxalate mono- and dihydrate under laminar flow in microfluidic devices

Crystallization of calcium oxalate (CaOx) was studied in microfluidic devices, with geometries simulating kidney stones collecting ducts, under laminar flow conditions relevant for kidney stone formation.

Pinning down the accuracy of physics-informed neural networks under laminar and turbulent-like aortic blood flow conditions.

Physics-informed neural networks (PINNs) are increasingly being used to model cardiovascular blood flow. The accuracy of PINNs is dependent on flow complexity and could deteriorate in the presence of highly-dynamical blood flow conditions, but the extent of this relationship is currently unknown. Therefore, we investigated the accuracy and performance of PINNs under a range of blood flow conditions, from laminar to turbulent-like flows. A stenosis was virtually induced in the thoracic segment of a patient's aorta to represent aortic coarctation. Stenosis severity was varied from 0% to 70% in increments of 5% (NCFD=15 cases), corresponding to stenotic Reynolds number that ranged from 1000 to 3333. CFD simulations at high spatial and temporal resolutions (6.9 million mesh, 10,000 time-steps) were performed for all NCFD=15 cases to obtain ground-truth velocity data. Fourier-based activation function in feed-forward PINNs with dynamic loss coefficients were trained to reconstruct CFD velocity field. Losses included those from physical equations, boundary conditions and sensor data sampled evenly from CFD simulations. Number of sensor points were increased from 200-1600 in increments of 200. This resulted in a total of 8 sensor point variations for each stenotic model (Nsens=8). Hence, a total of 120 (NCFDxNsens) cases were trained in this study. The PINNs architecture and data have been made open-sourced. PINNs errors increased substantially for stenosis severity >50% (stenotic Reynolds numer > 2000) due to the presence of complex turbulent-like flow features. When using 400 sensor points, PINNs velocity magnitude errors ranged from 30% for no-stenosis model to 57% for the model with 70% stenosis, and dropped to 10% and 20%, respectively when the number of sensor points were increased to 1600. PINNs velocity magnitude errors increased monotonically with turbulent intensity, particularly beyond stenosis severity of 50%. Our findings indicate that the accuracy of PINNs is dependent on the complexity of blood flow conditions. Using conventional PINNs architecture, the errors in trained velocity can increase substantially in the presence of turbulent-like blood flows that are typically found in various vascular pathologies.

TURBULENT MULTI-BRANCHING RADIAL SYMMETRIC FLOW STRUCTURES

This study builds upon previous research that developed optimized tree-shaped flow networks within disc-shaped bodies for enhanced thermal management, extending these principles to explore turbulent flow regimes. Previously, a multi-branching approach combined with strategic hydraulic diameter settings was utilized to balance thermal and fluid performance in laminar flow conditions, successfully minimizing flow resistance. These efforts revealed that symmetric tree designs could significantly boost hydraulic and thermal efficiencies via a constrained minimization approach. In the current work, the focus shifts to examining the implications of transitioning these optimized designs from laminar to turbulent flow conditions. By comparing performance metrics between the two regimes, this study aims to elucidate the effects of flow regime transitions on network efficiency and effectiveness. The results enhance understanding of the fundamental dynamics governing flow networks and guide the development of more robust designs capable of operating across a broader range of flow conditions.

ANALYSIS OF HEAT TRANSFER TO A SHEET-TYPE HEAT EXCHANGER PLACED IN RUNNING WATER-THERMAL ENERGY EXTRACTION FROM IRRIGATION WATER

A sheet-type heat exchanger has been extensively used as a device for extracting heat from the ground soil. This heat exchanger consists of polyethylene capillary tubes bundled together in a sheet, positioned between two header pipes that serve as the inlet and outlet for circulating brine. The bundled thin tubes, with an outer diameter of 6 mm and an inner diameter of 5mm, are highly flexible, allowing for easy winding and bending. This flexibility provides significant freedom in configuring the device within the soil. This paper examines the possibility of using the same heat exchanger to collect heat from water flowing in irrigation channels and rivers. We discuss an analytical method capable of predicting the performance of the heat exchanger when it is positioned parallel to the water flow. In this analysis, we employ the concept of overall heat transfer coefficient to evaluate a single polyethylene tube. Specifically, we determine the dimensionless inner convective heat transfer coefficient, known as the inner Nusselt number, for laminar flow conditions. Meanwhile, the outer convection heat transfer coefficient is derived from forced convection correlation obtained from an isothermal flat plate. Additionally, numerical simulations are conducted to account for the influence of header pipes on the flow field and to relax the assumption of a constant outer wall temperature. We find that the analytical and numerical results generally agree. Furthermore, we compare the analytically predicted results with available experimental data, revealing agreement between the predicted and experimentally obtained heat transfer rates.

Heat transfer and fluid flow characteristics of ring inserted riser tube in solar water heater

The present work considers the innovative design of absorber tube of solar water heater having circular rings inserts inside the riser tubes to provide optimal thermohydraulic performance of solar water heater having flat reflector beneath the absorber tubes. To produce substantial effect on the heat transfer rate, three different cases of absorbers with pitch ratio [Formula: see text] of 2, 3, and 4 have been considered. The influence of circular rings on heat transfer and fluid flow characteristics were experimentally evaluated and presented for laminar flow conditions. The data were collected at varying mass flow rates of 0.0056, 0.0097, 0.0138, 0.0207, 0.0277, and 0.0346 kg/s from 11:00 a.m. to 3:00 p.m. at intervals of 10 min in the month of March and April 2023 for all the three pitches considered. The results demonstrated that the maximum thermal efficiency and optimal performance evaluation factor of the solar water heater with ring inserted risers were found 83.92% and 1.7, respectively, for the pitch ratio 2. The Nusselt number and friction factor increased by 73.35%–91.88% and 29.72%–41.98%, respectively, in comparison to plain riser tube.

Deposition of nanoparticles through a cylindrical tube of human respiratory system

This paper proposes a mathematical model for nanoparticle deposition in the respiratory bronchiole of the human lung airways. The length of the respiratory bronchiole of the human lung is 1.2 mm, and the diameter is 0.5 mm. Therefore, to investigate the impact of inhaled nanoparticles within the lung bronchioles, first, we used the Navier–Stokes equation by including the Darcy term together with Newton’s equation of motion. Then we non-dimensionalized the governing equation, and numerical solutions are obtained using the finite difference technique. Under the assumption of laminar pulsatile flow conditions and axial symmetry, the problem is simplified to a two-dimensional computational domain. The computational framework is implemented using MATLAB R2018 through user-defined code. Velocity propagation, the Reynolds number, and the Darcy number effect are performed to examine the flow conditions inside the respiratory bronchioles.

Fluid flow simulation with an [formula omitted]-accelerated Boundary-Domain Integral Method

The development of new numerical methods for fluid flow simulations is challenging but such tools may help to understand flow problems better. Here, the Boundary-Domain Integral Method is applied to simulate laminar fluid flow governed by a dimensionless velocity–vorticity formulation of the Navier–Stokes equation. The Reynolds number is chosen in all examples small enough to ensure laminar flow conditions. The false transient approach is utilized to improve stability.As all boundary element methods, the Boundary-Domain Integral Method has a quadratic complexity. Here, the H2-methodology is applied to obtain an almost linear complexity. This acceleration technique is not only applied to the boundary only part but more important to the domain related part of the formulation. The application of the H2-methodology does not allow to use the rigid body method to determine the singular integrals and the integral free term as done until now. It is shown how to apply the technique of Guigiani and Gigante to handle the strongly singular integrals in this application. Further, a parametric study shows the influence of the introduced approximation parameters. For this purpose the example of a lid driven cavity is utilized. The second example demonstrates the performance of the proposed method by simulating the Hagen–Poiseuille flow in a pipe. The third example considers the flow around a rigid cylinder to show the behavior of the method for an unstructured grid. All examples show that the proposed method results in an almost linear complexity as the mathematical analysis promisses.

Computational and experimental analyses of pressure drop in curved tube structural sections of Coriolis mass flow metre for laminar flow region

ABSTRACT This research presents a comprehensive investigation into the computational and experimental aspects of pressure drop phenomena within the curved tube structures. Mass flow measurement holds critical significance in process industries to mitigate inaccuracies arising from fluid property variations. The CMFM stands as a reliable instrument for direct measurement; however, its performance has exhibited discrepancies, recording lower fluid flow magnitudes than actual values in laminar flow conditions. This anomaly is suspected to be attributable to a secondary force generated within the sensor's curved tube structure. This study seeks to elucidate this phenomenon by assessing the pressure drop resulting from the secondary flow in four distinct curved tube configurations: U, Omega, Delta, and Diamond shapes under steady-state conditions. The paper underscores the pressure drop characteristics inherent in each tube structure configuration, revealing that Basic U and Omega shaped tube structures exhibit the least pressure drop.

Assessment of pillar-array electrodes for electrochemical flow reactors using a novel hydrodynamic electrode performance factor

This work introduces and validates a Hydrodynamic Electrode Performance Factor (HEPF) for flow reactors. Traditional approaches to electrode optimization often rely on separated mass transfer and pressure drop metrics, hindering comparisons. We address this issue by combining electrochemical and hydrodynamic parameters through a new mathematical expression. This formulation draws inspiration from established equations in heat transfer and the widely recognized Chilton-Colburn analogy, aiming to develop a quantification method independent of the experimental arrangement. The HEPF is complementary to the well-established volumetric mass transfer coefficient and to Storck’s energetic effectiveness postulates for electrochemical reactors. Additionally, this study validates the proposed equation experimentally and then applies it to evaluate pillar array electrodes using 2D computational fluid dynamics simulations for laminar flow conditions. Both experimental and simulation approaches are used to analyze the hydrodynamic behaviour of the electrodes, utilizing the Forchheimer and Hagen-Poiseuille numbers. Notably, preliminary turbulence effects are observed at Reynolds numbers as low as 50 to 125. Visualization of velocity streamlines revealed distinct wake formation behind the pillars at these low Reynolds numbers. This study also explores how reactor inlets, outlets, and tubing pressure losses affect electrode performance. Results emphasize the importance of considering pressure drop, which is integral to the new hydrodynamic performance factor. Analysis of pillar array electrodes demonstrates that reducing both interpillar distance and pillar radius leads to improved electrochemical performance.

Enhancement of heat transfer characteristics in wavy microchannel heat sinks with streamlined micropins within convergent-divergent flow passages

In the current study, the heat transfer characteristics of a novel design microchannel with a wavy sinusoidal convergent-divergent wall structure featuring streamlined pins have been numerically investigated under laminar flow conditions. Various amplitudes, wavelengths, pin heights, and Reynolds numbers are considered as parameters. The thermal and hydraulic characteristics are analyzed in terms of Nusselt number, Fanning friction factor, and Performance Evaluation Criteria number (PEC), which evaluates the heat transfer enhancement against the associated pressure drop. It is revealed that increasing the amplitude and decreasing wavelength, along with moderate pin heights, significantly augment heat transfer. The streamlined pins effectively direct the flow, and the resulting secondary flow and chaotic advection considerably enhance heat transfer in the designed configuration. The study demonstrates that the heat transfer can be improved by a factor of 4.79 compared to a straight microchannel. Under these geometric and flow conditions, the pressure drop increases by a factor of 9.87, and the PEC is found to be around 2.23. A multi-objective optimization study using the Non-dominated Sorting Genetic Algorithm (NSGA-II) is conducted with Genetic Aggregation Response Surface Methodology to evaluate the impact of various parameters on thermal-flow performance and to identify the optimal design with material quantity variation. According to the optimal results, a 5 % increase in material can augment thermal-flow performance by approximately 206.6 % compared to traditional microchannels. Finally, practical correlations for the Nusselt number and friction factor, accounting for various parameters, have been developed to facilitate in designing of microchannel cooling systems.

Enhanced mixing characteristics of unbaffled U-shaped microreactor coupled oscillatory flow

The Microscale Oscillatory Flow Reactor (MOFR) can achieve good plug flow and micromixing performance simultaneously at laminar net flow conditions. An unbaffled U-shaped microreactor coupled with oscillating flow technology was designed to study the macro and micromixing performance. Firstly, the influence of oscillations on the flow performance was studied to reveal the formation rule of vortex. The simulation results showed that the continuous formation and destruction of periodic vortexes occurred in the microreactor with oscillation. With the increase of oscillation intensity, the vortex size in the radial direction first gradually increased and then becomes stable, and gradually moved axially, resulting in axial diffusion. Secondly, the effect of oscillation on the macromixing and micromixing performance were investigated. The results showed that the coupling oscillation could greatly improve the macromixing and micromixing performance. The macromixing and micromixing performance were promoted simultaneously at lower oscillation intensity and then tended to be flat due to the axial diffusion at high oscillation intensity. When φ>6.05, the minimum micromixing time and the maximum number of tanks can be achieved at the same time. At a velocity ratio of about 23, FoM reached a maximum of about 3.5.

Comparative Performance Assessment between Incompressible and Compressible Solvers to Simulate a Cavitating Wake

To study the effects of fluid compressibility on the dynamics of a cavitating vortex street flow in a regime where the vortex shedding frequency increases as a result of the cavitation increase, the cavitating wake behind a wedge was simulated employing both incompressible and compressible solvers. To do this, a compressible cavitation model was implemented, modifying the Zwart-Gerber-Belamri (ZGB) incompressible solver and including a pressure limit and absorbing boundary conditions to prevent a non-physical pressure field. To validate the performance of the compressible model, preliminary simulations were carried out on a 1D Sod cavitating tube and the cavitating vortex shedding behind a circular body at laminar flow conditions. The results of the cavitating wake behind the wedge with the incompressible and the compressible solvers showed similar predictions in terms of pressure, vortex shedding frequency, and instantaneous and average vapor volume fraction profiles. In spite of this, differences were obtained in the energy content of the fluid force fluctuations on the body at higher frequencies, which appear to be better resolved and amplified when the compressibility model is considered. Overall, both solvers provided comparable results in terms of cavitation phenomena that are well aligned with experimental observations.

Comparative investigation on heat transfer augmentation in a liquid cooling plate for rectangular Li-ion battery thermal management

This work conducted a numerical study with experimental validation to improve the performance of a rectangular multi-channel cooling plate utilised for cooling lithium batteries. Seven different designs on a cold plate for laminar flow conditions were evaluated using numerical modelling simulations in the 3D ANSYS program. Three cooling plate designs were proposed with channel arrangements: arc, convergent–divergent and different channel widths (narrow central channels and wide peripheral channels). The other four proposed cooling plate designs included representations of variable-sized pin fins with different shapes: oval, drop, rhombus and trapezoidal within different channel widths. Real experiments were conducted on a manufactured conventional cooling plate to verify the results of the numerical simulation. Results indicated that all proposed designs improved the heat transfer of the cooling plate. The percentage of enhancement in Nusselt number due to the presence of rhombus-shaped pin fins inside different channel widths is approximately 95.5 %, which is about three times the enhancement in pin fins that used only smooth different channel widths, which is approximately 33.5 %. Amongst the studied designs, incorporating different channel widths with the addition of rhombus-shaped pin fins exhibited the largest heat dissipation capacity and the best thermal–hydraulic performance. The highest temperature uniformity enhancement ratio and performance evaluation parameter for this case reached about 71.96 % and 1.68, respectively.