Channel Geometry Parameters Research Articles

Salt scaling dynamics in microfluidic channels: Impact of channel geometry and process parameters

Salt scaling, a prevalent challenge in industrial processes, often leads to reduced efficiency, equipment failure, and environmental impact. Understanding and mitigating scaling in miniaturized systems for process intensification applications is crucial. In this study, we indigenously developed and utilized microfluidic reactors to investigate calcium carbonate (CaCO3) scaling dynamics in microfluidic channels, offering real-time visualization under continuous flow; a significant advancement over static methods. We explore the impact of channel geometry (curvature of 0°, 45°, 90°, and 135°) and process parameters (temperature, supersaturation index (SI), and flow velocity) on CaCO3 deposition behavior. Our findings reveal significant influences: higher temperature and SI promote deposition, while microchannel curvature and increased flow velocity enhance removal. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the morphology and phase changes of the deposited CaCO3. Calcite and aragonite were the dominant polymorphs, with their occurrence influenced by temperature and SI. These insights can be translated to the design and operation of miniaturized equipment for process intensification, such as micro heat exchangers. By understanding and controlling scaling phenomena, this research might pave the way for improved performance, sustainability, and resource efficiency in various industrial settings.

Theoretical investigation of hysteresis loops in free-surface flow under sluice gates for power-law channels

ABSTRACT In the present study, a new theoretical framework and analytical solutions to the problem of hysteresis loops due to hydraulic jump in power-law open channels under supercritical flows are introduced. This investigation primarily focuses on the flow dynamics encountered at a vertical sluice gate across channels of various shapes: rectangular, parabolic, and triangular. By the application of energy and momentum conservation principles, the dual flow configurations emerging under identical initial conditions are shown. An intensive analytical computational analysis led to the development of approximate theoretical models, facilitating the prediction of hysteresis loops for a wide range of Froude numbers and dimensionless channel geometry parameters. Several illustrative examples were treated and the results show a high degree of accuracy of the proposed models in predicting the hysteresis loops. The present research contributes to a novel methodology for enhancing predictions regarding the behavior of supercritical flows and the design of open channels for specific scenarios of the hysteresis phenomenon.

Validation of Fluid Flow Speed Behavior in Capillary Microchannels Using Additive Manufacturing (SLA Technology)

This research explores fluid flow speed behavior in capillary channels using additive manufacturing, focusing on stereolithography (SLA). It aims to validate microchannels fabricated through SLA for desired fluid flow characteristics, particularly capillary-driven flow. The methodology involves designing, fabricating, and characterizing microchannels via SLA, with improvements such as an air-cleaning step facilitating the production of microchannels ranging from 300 to 1000 µm. Experimental validation assesses fluid flow speed behavior across channels of varying dimensions, evaluating the impact of channel geometry, surface roughness, and manufacturing parameters. The findings affirm the feasibility and efficacy of SLA in producing microchannels with consistent and predictable fluid flow behavior between 300 to 800 µm. This study contributes insights into microfluidic device fabrication techniques and enhances the understanding of fluid dynamics in capillary-driven systems. Overall, it underscores the potential of additive manufacturing, specifically SLA, in offering cost-effective and scalable solutions for microfluidic applications. The validated fluid flow speed behavior in capillary channels suggests new avenues for developing innovative microfluidic devices with improved performance and functionality, marking a significant advancement in the field.

Numerical study of the process parameters affecting the feature size of a microfiber fabricated by microfluidic-based bioprinting

Microfiber is a significant tubular structure due to its desirable properties, such as a large surface area and near-vessel shape. However, the fabrication of solid and hollow microfibers may face challenges with additive manufacturing (AM). 3D bioprinting is an AM technique with significant challenges, such as difficulty in high-precision printing of precise microfibers. Additionally, due to the unique advantages of microfluidic systems, such as flow control, laminar regime, and biocompatibility, these devices have great potential to integrate with 3D bioprinting. Therefore, enhancing AM methods with microfluidic technology is a prominent approach to fabricating heterogeneous microfibers. Several process parameters affect the geometry of microfibers produced by microfluidic-based printing platforms. Therefore, this study has focused on the numerical analysis of channel geometry, bioink properties, and process parameters on the microfibers’ feature size. In this regard, the results of the developed numerical model have been verified with experimental data. There is 85% agreement between the numerical model results and experimental data. These errors are attributed to the sheath fluid and sample fluid effects. Besides, a mathematical model was developed to predict the solid and hollow microfiber feature size. Altering the sample and sheath inlet velocity resulted in a range of solid microfiber diameters between 45 and 108 µm. The OD values have an error margin of up to 15%, while the ID error values have an error margin of up to 14%. The results of this study can be employed to optimize the channel geometry, bioink properties, and process parameters to achieve the desired functionally graded microfibers.

A membrane’s blueprint: In silico investigation of fluid flow and molecular transport as a function of membrane design parameters in organ-on-a-chip

Following the rapid growth of Organ-on-a-Chip (OoaC) technology, porous membranes have become essential components for in vitro tissue barrier models. Nonetheless, literature highlights lacking knowledge on their integration and effect on microfluidic devices. Therefore, we conducted finite element modelling (FEM) to characterize the influence of membrane, channel geometry, flow and diffusion parameters, in modelling flow rate, shear stress, transient transport and steady state molecular concentration. This analysis was performed for four different conditions based on single channel (SCP) and parallel perfusion (PP). It was found that membrane and geometry parameters are crucial in determining flow and shear for SCP. However, for PP, flow and shear are predominantly governed by the inlet flow rate. Although the transient behaviour is well-controlled within SCP and PP, only PP allows modelling the steady state concentration distribution. It is highlighted that: (1) the pore radius has great influence on flow and shear; (2) a shallow cell channel and a long membrane are capable of establishing different levels of shear on opposing surfaces of the same channel; (3) the membrane thickness, membrane length, height of the cell and flow channels, and inlet flow rate provide good control over transient transport; (4) the membrane length and inlet flow rate enable changing the concentration from a uniform distribution to a complete heterogeneous state across the device. Experimental assays were performed to support the FEM and evidence its significance for OoaC applications. Ultimately, extensive, and systematic guidelines are provided on designing future OoaC devices with integrated porous membranes.

Development and evaluation of the channel routing model and parameters within the National Water Model

AbstractThe National Water Model (NWM) was deployed by the National Oceanic and Atmospheric Administration to simulate operational forecasts of hydrologic states across the continental United States. This paper describes the geospatial river network (“hydro‐fabric”), physics, and parameters of the NWM, elucidating the challenges of extrapolating parameters a large scale with limited observations. A set of regression‐based channel geometry parameters are evaluated for a subset of the 2.7 million NWM reaches, and the riverine compound channel scheme is described. Based on the results from regional streamflow experiments within the broader NWM context, the compound channel reduced the root mean squared error by 2% and improved median Nash–Sutcliffe efficiency by 16% compared with a non‐compound formulation. Peak event analysis from 910 peak flow events across 26 basins matched from the US Flash Flood Observation Database revealed that the mean timing error is 3 h lagged behind the observations. The routing time step was also tested, for 5‐min (default, operational setting) and 1‐h increments. The model was computationally stable and able to convey the flood peaks, although the hydrograph shape and peak timing were altered.

EXPERIMENTAL RESEARCH ON A KINETIC HYDRO TURBINE - GENERATOR ASSEMBLY

The present paper is part of a larger project whose purpose is to develop a new hydrokinetic turbine-generator assembly, suitable for very low head water courses. It presents the experimental results of a turbine–generator physical model, installed on the tailrace of Mihailesti Hydropower Plant. In order to carry out the measurements, a floating structure and an anchoring system was installed on the power plant tailrace. This system also allowed the translation of the assembly between the two shores. A first set of measurements followed the water velocity and depth in the channel at various load values of the hydropower plant units, in order to determine the proper conditions for testing the model. The turbine gives the possibility of blades adjustment at three different angles, 0, 9 and 14 degrees respectively. Therefore, a set of measurements has been performed for each position of the blades. The measured parameters were the electric parameters of the generator such as voltage, current and the power variation with rotation speed. For the blades adjustment of 9 degrees and 1.76 m/s water velocity, the generator reached its maximum power of 500 W. The results retrieved will be used for the optimization and design of a new enlarged scale turbine–generator assembly. They will also be used as input data for the numerical modeling of the generator. Also, the exact knowledge of the channel geometry and flow parameters is valuable in studies preceding testing a prototype in the site.

Evaluation of a new observationally based channel parameterization for the National Water Model

Abstract. Accurate representation of channel properties is important for forecasting in hydrologic models, as it affects the height, celerity, and attenuation of flood waves. Yet, considerable uncertainty in the parameterization of channel geometry and hydraulic roughness (Manning's n) exists within the NOAA National Water Model (NWM), due largely to data scarcity; only ∼2800 out of the 2.7×106 river reach segments in the NWM have measured channel properties. In this study, we seek to improve channel representativeness by updating channel geometry and roughness parameters using a large, previously unpublished hydraulic geometry (HyG) dataset of approximately 48 000 gauges. We begin with a Sobol' sensitivity analysis of channel geometry parameters for 12 small, semi-natural basins across the continental U.S., which reveals an outsized sensitivity of simulated flow to Manning's n relative to channel geometry parameters. We then develop and evaluate a set of regression-based regionalizations of channel parameters estimated using the HyG dataset. Finally, we compare the model output generated from updated channel parameter sets to observations and the current NWM v2.1 parameterization. We find that while the NWM land surface model holds the most influence over flow, given its control over total volume, the updated channel parameterization leads to improvements in simulated streamflow performance relative to observed flows, with a statistically significant mean R2 increase from 0.479 to 0.494 across approximately 7400 gauge locations. HyG-based channel geometry and roughness provide a substantial overall improvement in channel representation over the default parameterization, updating the previous set value for most reaches of Manning's n=0.060 to a new range between 0.006 and 0.537 (median 0.077). This research provides a more representative, observationally based channel parameter dataset for the NWM routing module and new insight into the influence of the routing module within the overall modeling framework.

Response of Channel Morphology to Climate Change over the Past 2000 Years Using Vertical Boreholes Analysis in Lancang River Headwater in Tibetan Plateau

The Qinghai-Tibetan Plateau, known as the world’s “third pole”, is home to several large rivers in Asia. Its geomorphology is exceptionally vulnerable to climate change, which has had a significant impact on historical riverbed development through runoff and sedimentation processes. However, there is limited research combining climate change, sedimentology, and chronology with river dynamics to investigate riverbed evolution patterns in geological-historical time scales and their changes in overland flow capacity. In the current study, the evolution of a representative portion of the river channel in the Nangqian basin in the Lancang River headwaters was investigated to explore the reaction of the riverbed to climatic change during the geological period via field surveys, riverbed drilling, optically stimulated luminescence (OSL) dating and bankfull channel geometry parameters. The generalized channel section of the historical period was obtained by linking sedimentary layers of the same age on the distribution map of borehole sections, and the bankfull area of the river was computed accordingly. The restored bankfull areas can effectively reflect the ability of historical river channels to transport water and sediment, thus reflecting the climate change at that time. The findings showed that river morphology in the mounded river section could be successfully reconstructed using OSL dating and sedimentary records and that the conceptual sections of the historical warm periods at 2000 years (2 ka) and 0.7 ka can be recovered. Based on the reconstruction, the calculated bankfull areas during the two warm events were larger than present by factors of 1.28 and 1.9, respectively, indicating a stronger capacity for transporting water and sediments. This is the first trial in the Lancang headwaters to investigate the response of river morphology to climate change on a geological time scale.

Characterization of microbubble-enhanced molecular delivery to cells in acoustofluidic channels

Cell therapies are rapidly emerging as a promising approach for treatment of many diseases, such as cancer and cardiovascular diseases. Non-viral methods for molecular delivery are currently in development to increase safety and reduce varability during manufacturing of cell therapies. Ultrasound-mediated microbubble cavitation has been utilized as an effective approach for non-viral molecular delivery via sonoporation or other mechanisms. However, prior ultrasound studies have primarily utilized static sample chambers, which have limited throughput and are generally not practical for cell therapy manufacturing processes. To address these limitations, we are developing novel acoustofluidic platforms to enable intracellular delivery of biomolecules as cells continuously pass through an ultrasound field in a flow chamber. We have investigated a range of fundamental parameters that influence acoustofluidic-mediated molecular delivery to human cells, including microbubble properties, channel geometry, and ultrasound parameters. In addition, we investigated biological factors that influence acoustofluidic-mediated molecular delivery to cells, including cellular properties and extracellular metabolite levels. The results of these studies will be presented to provide new insights into the key parameters and mechanisms that affect the efficiency of molecular delivery to human cells in acoustofluidic channels. Further development of acoustofluidic platforms may enable improved processes for manufacturing of cell therapies.

Inertial microfluidics: Determining the effect of geometric key parameters on capture efficiency along with a feasibility evaluation for bone marrow cells sorting.

Despite great developments in inertial microfluidics, there is still a lack of knowledge to precisely define the particles' behavior in the microchannels. In the present study, as a prerequisite to experimental studies, numerical simulations have been used to study the capture efficiency of target particles in the contraction-expansion microchannel, aiming to provide an estimation of the conditions at which the channel performs best. Fluid analysis based on Navier-Stokes equations is conducted using the finite element method to determine the streamlines and vortices. The highest capture efficiency for 10, 15, and 19-micron particles occurs when the center of the vortex is approximately in the middle of the wide section (at the flow rate of 0.35ml/min). In addition to investigating the effect of particle diameter and input flow rate, the effect of channel geometry parameters (channel height and initial length of the channel) on particle trapping has also been studied. Also, to consider great interest in separating different-sized bioparticles from a sample, a three-stage platform has been designed to separate four types of bone marrow cells and evaluate the possibility of using contraction-expansion channels in this application.

Inertial particle separation in helical channels: A calibrated numerical analysis

Inertial microfluidics has been used in recent years to separate particles by size, with most efforts focusing on spiral channels with rectangular cross sections. Typically, particles of different sizes have been separated by ensuring that they occupy different equilibrium positions near the inner wall. Trapezoidal cross sections have been shown to improve separation efficiency by entraining one size of particles in Dean vortices near the outer wall and inertially focusing larger particles near the inner wall. Recently, this principle was applied to a helical channel to develop a small-footprint microfluidic device for size-based particle separation and sorting. Despite the promise of these helical devices, the effects of channel geometry and other process parameters on separation efficiency remain unexplored. In this paper, a simplified numerical model was used to estimate the effect of various geometric parameters such as channel pitch, diameter, taper angle, depth, and width on the propensity for particle separation. This study can be used to aid in the design of microfluidic devices for optimal size-based inertial particle separation.

Optimization of anode performance in the ethanol electrochemical reforming for clean hydrogen production

Carbon-based fuel electrochemical reforming is considered as a promising hydrogen production method. Ethanol is one of the most appropriate carbon-based fuels. In this work, anode performance, especially the flow, ethanol electro-oxidization and energy consumption in the ethanol electrochemical reforming is numerically studied and experimental verified. Take the straight serpentine channel with square cross-section as a base structure in the electrochemical cell (EC), the effects of channel geometry and operating parameters are analyzed. Another five different configurations of flow channels, as well as another three different cross-sections are designed and explored. Results indicate that at the same cross-section area, the wider channel provides the higher effective area for proton transfer, and thereby improves the electrode reactions. The appropriate decrease of inlet velocity or increase of input voltage promotes the anode reaction and reduces the pressure drop in channel, while the operating temperature has the opposite effects on ethanol conversion and pressure drop. The arc channel is found optimal considering its highest ethanol conversion, although its pressure drop is a bit higher. The sector cross-section with uniform flow field distribution is found most favorable for the straight serpentine channel considering the ethanol electro-oxidization. These findings will favor the improvement of EC.

Analysis and optimization of high temperature proton exchange membrane (HT-PEM) fuel cell based on surrogate model

The stoichiometric ratio and flow channel geometry play a vital role in the performance of high temperature proton exchange membrane (HT-PEM) fuel cells. Because of the high cost of experiments or simulations, most analyses and optimization of the stoichiometric ratio and flow channel geometry are limited to several points in the entire design domain. In this study, an analysis and optimization method for HT-PEM fuel cells based on the surrogate model was proposed. Surrogate models were constructed using some of the available budgets of samples to analyze and optimize the entire design domain. With this method, it was indicated that the effect of the cathode stoichiometric ratio is more significant to the cell performance than the anode stoichiometric ratio and there are significant nonlinear interactions among the flow channel geometry parameters. At the fixed operating voltage, the flow channel geometry with the maximum current density and that with the maximum real power were obtained. Compared with the base design, the designs obtained by the surrogate model improve the current density and real power by 10.54% and 3.93%, respectively. Thus, this analysis and optimization method is demonstrated to be helpful and deserves attention in future research.

Desain Saluran Terbuka Berbasis Microsoft Excel Perhitungan dan Pemodelan yang Praktis dan Effisien

Saluran dibangun sebagai media yang berfungsi untuk mengalirkan air. Di dalam kegiatan perencanaan, desain, dan konstruksi saluran memerlukan banyak waktu, upaya , dan biaya. Desain dan konstruksi saluran harus sesuai dengan kebutuhan dan karakteristik lokasi yang digunakan. Seringkali terjadi perubahan parameter dalam menentukan desain saluran akibat pertimbangan teknis maupun ekonomis. Hal tersebut menuntut perubahan desain saluran yang sesuai dengan parameter yang baru. Oleh sebab itu, diperlukan alat untuk mempermudah perhitungan desain saluran. Parameter yang diperlukan untuk menghitung desain saluran adalah debit (Q), faktor tahanan Chezy (C), Koefisien Darcy-Weisbach (f), atau faktor kekasaran Manning (n), dan parameter gradien alas saluran (i). Penelitian bertujuan untuk menghitung dan memodelkan desain saluran, serta menyediakan alat atau media praktis dan mudah digunakan. Metode yang dilakukan adalah dengan menerapkan formula perhitungan Chezy, Darchy-Weisbach, dan Manning untuk berbagai bentuk saluran menggunakan perangkat lunak Microsoft Excel. Penentuan nilai faktor tahanan Chezy (C), Koefisien Darcy-Weisbach (f), dapat dihubungkan dari faktor kekasaran Manning (n). Koefisien kekasaran Manning (n) dapat diperkirakan dari ukuran partikel material penyusun alas saluran (d) menggunakan formula, maupun mengacu kepada tabel faktor kekasaran Manning. Penelitian ini menghasilkan alat untuk menghitung dan memodelkan desain saluran terbuka “Kalkulator Desain Saluran – FAR”. Penulis mengusulkan formula baru untuk memperkirakan nilai faktor kekasaran Manning (n) dari ukuran partikel material penyusun alas saluran (d). Selain itu, penulis mengusulkan formula untuk menghitung langsung tinggi air dalam penampang geometri saluran (y). Formula tersebut diperoleh dengan memasukkan koefisien α yang berdasar dari hubungan antar parameter geometri saluran kedalam formula Chezy, Darchy-Weisbach, dan Manning.
 Kata Kunci: alat, desain, geometri, praktis, saluran.

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

AbstractLateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two‐step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non‐cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel‐system geometry (i.e. channel‐bank heights, water depths, channel‐system width, and channel slope) on channel‐migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel‐migration rates scale inversely with the channel‐bank height. Furthermore, when channel‐bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel‐migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank‐height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel‐migration rates by modulating channel‐bank heights. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd.

Effect of geometry parameters on the hydrocarbon fuel flow rate distribution in pyrolysis zone of SCRamjet cooling channels

Hypersonic air-breathing propulsion (>Mach 5) based on SCRamjet promotes the revolutions of both military and civilian applications. However, the engine thermal protection is seriously challenged due to high Mach number. One of the key problems is mal-distribution of hydrocarbon fuel in regenerative cooling channels under the complex thermal boundaries and channel geometry, which may cause structural failure. To improve the cooling channel design and achieve better fuel flow distribution, the effect of channel geometry parameters on flow distribution in pyrolysis zone is numerically studied. Both geometry induced and heat flux induced flow mal-distribution are concerned. The study indicates that the flow and heat transfer features in pyrolysis zone of parallel channels differs with those in non-pyrolysis zone. The flow distribution deviations in pyrolysis zone are lower. When the channel aspect ratio varies, thermal stratification dominates flow distribution more than the variation of heat flux on heated surface in pyrolysis zone, which is opposite of that in non-pyrolysis zone. Besides, thinner rib and smaller total flow area achieve better cooling performance while consuming less fuel chemical heat sink. The results help to conclude possible references to the design of cooling channels with fuel pyrolysis considered.

Flow rate limitation in curved open capillary groove channels

This paper is concerned with the forced flow through curved open capillary channels under microgravity conditions. A maximum flow rate in the open capillary channel achieves when the flow rate exceeds a certain value and the free surface collapses leading to the gas ingestion. The gas ingestion is not desired for most of the applications. In order to prevent it and enable an optimal performance, it is vital to understand the influences of the channel geometry parameters and liquid properties on the maximum flow rate. In this paper, the one-dimensional theoretical model successfully applied to the straight open capillary channel is extended to the curved open capillary channel. The result shows that under the same boundary conditions, the maximum flow rate in the curved open channel is smaller than that in the straight open channel. The maximum flow rate decreases with the curvature of open channel increasing. By analysis, the pressure loss and the centrifugal force effect due to the curve motion in a curved path are considered to be the cause of the maximum flow rate difference between the curved channel and the straight channel. It is found that the centrifugal force effects weaken the pressure difference balance ability of the free surface and the pressure loss in the curved open channel is greater than that in the straight open channel. By comparison, the one-dimensional theoretical results agree well with CFD simulations and the average relative error is only 1.51%. Furthermore, the parametric study of flow in the curved open capillary channel depicts that the maximum flow rate increases with the channel curvature or aspect ratio increasing, and decreases with the open channel length, contact angle or Ohnesorge number increasing. This conclusion can be utilized to design the open channel in space liquid management system.

Enhancement of Heat Transfer over a Double Forward Facing Step with Square Obstacle through Taguchi’s Optimization Technique

In this paper, the heat transfer to the fluid, passing through the double forward facing step (FFS) channel with square obstacle is enhanced by Taguchi’s S/N ratio analysis. Flow through the forward facing step channel has a wide range of applications in thermal systems due to its flow separation and subsequent reattachment, which in turn enhances the heat transfer. Flow separation and reattachment mainly depends on the channel geometry, obstacle and flow parameters. Hence, in this study, step height in the channel, obstacle size, Reynold’s number and gap between the obstacle and step are included as control paramters in the S/N ratio analysis for maximizing the heat transfer. These parameters are varied through three levels of values and L9 orthogonal array is employed. Numerical simulation technique is applied to analyze the L9 cases through computational fluid dynamics code. From the simulation, the rise in temperature at the channel exit with reference to the inlet is predicted. The best values for the identified control parameters conclude to a temperature raise of about 2.86°C. The optimum result obtained from the S/N ratio analysis is also compared with response surface methodology technique. Finally, analysis of variance (ANOVA) is conducted and identified that step height and flow Reynold’s number affect the heat transfer by about 79 and 19%, respectively.

DESIGN AND SIMULATION OF MICROFLUIDIC PASSIVE MIXER WITH GEOMETRIC VARIATION

Microfluidic designs are advantageous and are extensively used in number of fields related to biomed ical and biochemical engineeri ng. The objective of this paper is to perform numerical simulations to optimize the design of microfluidic mixers in order to achieve optimum mixing. In the present study, fluid mixing in different type of micro channels has b een investigated. Numeric al si mulations are performed in order to understand the effect of channel geometry parameters on mixing p erformance. A two dimensional “ T shaped ” passive microfluidic mixer is restructured by employing the rectangular shaped obstacles in the chan nel to improve the mixing performance. The impact of proper placement of obstacles in the channel is demonstrated b y applying the leakage concept. It has been observed that, the channel design with non - leaky obstacles (i.e. without leaky barriers) has presented better mi xing performance in contrast to channel design with leaky obstacles (i.e. leaky barriers) and channe l design without obstacles. The mixing occurs by virtue of secondary flow and generation of vortices due to curling o f fluids in the channel o n account of t he presence of obstacles. This passive mixer has achieved complete mixing of fluids in few seconds o r some milliseconds , which is certainly acceptable to utilize in biological applications such as cell dynamics, drug scre ening , toxicological screening and others.