scholarly journals Evolution of Water-in-Oil Droplets in T-Junction Microchannel by Micro-PIV

2021 ◽  
Vol 11 (11) ◽  
pp. 5289
Author(s):  
Hawa Ringkai ◽  
Khairul Fikri Tamrin ◽  
Nadeem Ahmed Sheikh ◽  
Shahrol Mohamaddan
Keyword(s):  
Flow Characteristics ◽  
Microfluidic Channel ◽  
Distilled Water ◽  
Critical Factors ◽  
Polystyrene Microspheres ◽  
Oil Droplets ◽  
Cross Sectional ◽  
Micro Piv ◽  
Interfacial Surface ◽  
Minimal Difference

Water-in-oil droplets have huge importance in chemical and biotechnology applications, despite their difficulty being produced in microfluidics. Moreover, existing studies focus more on the different shape of microchannels instead of their size, which is one of the critical factors that can influence flow characteristics of the droplets. Therefore, the present work aims to study the behaviours of water-in-oil droplets at the interfacial surface in an offset T-junction microchannel, having different radiuses, using micro-PIV software. Food-grade palm olein and distilled water seeded with polystyrene microspheres particles were used as working fluids, and their captured images showing their generated droplets’ behaviours focused on the junction of the respective microfluidic channel, i.e., radiuses of 400 µm, 500 µm, 750 µm and 1000 µm, were analysed via PIVlab. The increasing in the radius of the offset T-junction microchannel leads to the increase in the cross-sectional area and the decrease in the distilled water phase’s velocity. The experimental velocity of the water droplet is in agreement with theoretical values, having a minimal difference as low as 0.004 mm/s for the case of the microchannel with a radius of 750 µm. In summary, a small increase in the channel’s size yields a significant increase in the overall flow of a liquid.

Flow Characteristics of Dilute Polymer Solutions in Micro Tubes

2007 ◽  
Author(s):  
Keizo Watanabe ◽  
Satoshi Ogata ◽  
Munehiko Hirao
Keyword(s):  
Flow Rate ◽  
Polymer Solutions ◽  
Flow Characteristics ◽  
Fused Silica ◽  
Flow Rate Ratio ◽  
Distilled Water ◽  
Number Range ◽  
Micro Piv ◽  
Dilute Polymer Solutions ◽  
Piv Measurement

Pressure drops and velocity profiles for micro tubes were investigated for the laminar flow of distilled water and dilute polymer solutions. The test micro tubes were fused silica capillaries with diameters in the range of 50.2–251.8 μm, and a value of l/d (length/diameter) of about 340. By performing pressure drop measurements, it is shown that the experimental data agree well with the Hagen-Poiseuille equation in the case of Newtonian fluids. On the other hand, the flow rate of dilute polymer solutions increases relative to that of distilled water in the low Reynolds number range. The increased flow rate ratio is a maximum of about 15% in the case of d = 251.8 μm. For the result of the micro PIV measurement, however, there are few differences between the velocity profile of distilled water and the Peo 5 ppm solution.

scholarly journals Bayesian Optimization Design of Inlet Volute for Supercritical Carbon Dioxide Radial-Flow Turbine

Machines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 218
Author(s):  
Chao Bian ◽  
Shaojie Zhang ◽  
Jinguang Yang ◽  
Haitao Liu ◽  
Feng Zhao ◽  
...  
Keyword(s):  
Optimization Design ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Bayesian Optimization ◽  
Working Fluid ◽  
Cross Sectional ◽  
Pressure Loss Coefficient ◽  
Flow Capacity ◽  
Cycle Efficiency ◽  
Total Pressure Loss Coefficient

The radial-flow turbine, a key component of the supercritical CO2 (S-CO2) Brayton cycle, has a significant impact on the cycle efficiency. The inlet volute is an important flow component that introduces working fluid into the centripetal turbine. In-depth research on it will help improve the performance of the turbine and the entire cycle. This article aims to improve the volute flow capacity by optimizing the cross-sectional geometry of the volute, thereby improving the volute performance, both at design and non-design points. The Gaussian process surrogate model based parameter sensitivity analysis is first conducted, and then the optimization process is implemented by Bayesian optimization (BO) wherein the acquisition function is used to query optimal design. The results show that the optimized volute has better and more uniform flow characteristics at design and non-design points. It has a smoother off-design conditions performance curve. The total pressure loss coefficient at the design point of the optimized volute is reduced by 33.26%, and the flow deformation is reduced by 54.55%.

scholarly journals INFLUENCE OF WI-FI PERFORMANCE ON STUDENTS' SATISFACTION

2021 ◽  
Vol 3 (8) ◽  
pp. 226-237
Author(s):  
Nor Ain Najwa Ismail ◽  
Nur Atikah Armieza Khairul Nazmi ◽  
Nur Aishah Abdul Razak ◽  
Nurulnur Athirah Azhar ◽  
Rozilawati Shaari ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Service Quality ◽  
Multiple Regression Analysis ◽  
Learning Process ◽  
Critical Factors ◽  
Cross Sectional ◽  
Single Cross ◽  
Cross Sectional Studies ◽  
Students Satisfaction ◽  
Survey Questionnaires

Wi-Fi services provided by institutions are critical factors helping students in their learning process, especially during the COVID-19 pandemic. However, studies concerning Wi-Fi performance on students’ satisfaction in Polytechnics Malaysia are limited. Hence, this study aims to investigate the influence of Wi-Fi service quality on students’ satisfaction, particularly in the Politeknik Tuanku Syed Sirajuddin (PTSS) context. Specifically, this study examines the influence of reliability, tangibility, responsiveness, assurance, and empathy on students’ satisfaction towards Wi-Fi performance. Quantitative and single cross-sectional studies were employed. A total of 260 students responded to the survey questionnaires. Multiple regression analysis results revealed that reliability, tangibility, responsiveness, assurance, and empathy influence students’ satisfaction. It shows that improving reliability, tangibility, responsiveness, assurance, and empathy is very important to increase students’ satisfaction. The results also indicated that responsiveness is the primary factor influencing students’ satisfaction. This study is hoped to enlighten the polytechnic management to improve Wi-Fi performance for the students.

Analysis of Flow Resistance Inside Microchannels With Different Inlet Configurations Using Micro-PIV System

2003 ◽  
Author(s):  
Sang-Joon Lee ◽  
Guk-Bae Kim
Keyword(s):  
Flow Resistance ◽  
Reduction Rate ◽  
Flow Characteristics ◽  
Entrance Region ◽  
Curvature Radius ◽  
Microfluidic Chips ◽  
Mean Velocity ◽  
Dimethyl Siloxane ◽  
Micro Piv ◽  
Macro Scale

Most microfluidic chips consist of several microchannels inside. In order to design microfluidic chips efficiently, it is important to predict the flow passage and to understand the flow characteristics on the chip. In this study, the flow structure inside microchannels has been investigated using a micro-PIV system. We focused on the flow resistance with respect to the inlet configuration of microchannels. The microchannels made of poly-dimethyl-siloxane (PDMS) material were fabricated by a micro-molding technique using SU-8 (photoresist) master. The width (w) and depth of the microchannels were fixed as 100 μm and 58 μm, respectively. Six different inlet configurations with curvature radii in the ranges from r = 0.2w to 1.5w were tested in this study. As a result, with increasing the curvature radius of the inlet corner, the streamwise mean velocity develops slowly in the entrance region, but the fully developed velocity at further downstream is increased. When the curvature radius is larger than r = 0.6w, the reduction rate of flow resistance is not so significant. For the microchannels with r = 0.6w, 0.8w and 1.0w the downstream mean velocity at channel center has nearly the same value of about 276 mm/sec, 10.5% larger than that of r = 0.2w. The simple rounding of microchannel inlet corner reduces flow resistance effectively by smoothing the incoming flow. The length of entrance region is much smaller than that of macro-scale channel.

scholarly journals Performance and Exit Flow Characteristics of Mixed-Flow Turbines

1997 ◽  
Vol 3 (4) ◽  
pp. 277-293 ◽  
Author(s):  
C. Arcoumanis ◽  
R. F. Martinez-Botas ◽  
J. M. Nouri ◽  
C. C. Su
Keyword(s):  
Steady State ◽  
Velocity Ratio ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Mixed Flow ◽  
Cross Sectional ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
And Performance ◽  
Inlet Angle

The performance and exit flow characteristics of two mixed-flow turbines have been investigated under steady-state conditions. The two rotors differ mainly in their inlet angle geometry, one has a nominal constant incidence (rotor B) and the other has a constant blade angle (rotor C), but also in the number of blades. The results showed that the overall peak efficiency of rotor C is higher than that of rotor B. Two different volutes were also used for the tests, differing in their cross-sectional area, which confirm that the new larger area volute turbine has a higher efficiency than the old one, particularly at lower speeds, and a fairly uniform variation with velocity ratio.The flow exiting the blades has been quantified by laser Doppler velocimetry. A difference in the exit flow velocity for rotors B and C with the new volute was observed which is expected given their variation in geometry and performance. The tangential velocities near the shroud resemble a forced vortex flow structure, while a uniform tangential velocity component was measured near the hub. The exit flow angles for both rotor cases decreased rapidly from the shroud to a minimum value in the annular core region before increasing gradually towards the hub. In addition, the exit flow angles with both rotors were reduced with increasing rotational speeds. The magnitude of the absolute flow angle was reduced in the case of rotor C, which may explain the improved steady state performance with this rotor. The results also revealed a correlation between the exit flow angle and the performance of the turbines; a reduction in flow angle resulted in an increase in the overall turbine efficiency.

Flow Characteristics of Pulsating Flow Obstructed by an Array of Square Rods

2000 ◽  
Author(s):  
Hiroyuki Murata ◽  
Ken-ichi Sawada ◽  
Michiyuki Kobayashi
Keyword(s):  
Pressure Gradient ◽  
Flow Characteristics ◽  
Pulsating Flow ◽  
Pulsation Period ◽  
Simulation Code ◽  
Cross Sectional ◽  
Gradient Parameter ◽  
Streamwise Pressure Gradient ◽  
Time Variations ◽  
Visualization Experiments

Abstract A series of flow visualization experiments of pulsating flow obstructed by an array of square rods was carried out to investigate its characteristics. When the pulsation is absent, Karman vortices shed periodically from each rod. When the pulsation period is relatively long compared with the shedding period and its amplitude is large, the flow is stabilized during the accelerating phase and, during the decelarating phase, the flow is destabilized and Karman vortices break down. When the pulsation period is shorter than shedding period and its amplitude is large, the flow pulsation controls the generation and breakdown of the Karman vortices. A numerical simulation code was developed and compared with the experimental results. When the pressure gradient parameter of the code is changed sinusoidally with time, computed results become the pulsating flow. Time variations of the streamwise pressure gradient and cross-sectional averaged velocity show similarity between the experimental and computed results.

scholarly journals Flattening of Diluted Species Profile via Passive Geometry in a Microfluidic Device

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 839
Author(s):  
Michael Miles ◽  
Biddut Bhattacharjee ◽  
Nakul Sridhar ◽  
Apresio Kefin Fajrial ◽  
Kerri Ball ◽  
...  
Keyword(s):  
Solute Transport ◽  
Concentration Profile ◽  
Microfluidic Channel ◽  
Region Of Interest ◽  
Solute Concentration ◽  
Cross Sectional ◽  
Driven Systems ◽  
Solute Profile ◽  
Dynamics Simulations ◽  
Pressure Driven

In recent years, microfluidic devices have become an important tool for use in lab-on-a-chip processes, including drug screening and delivery, bio-chemical reactions, sample preparation and analysis, chemotaxis, and separations. In many such processes, a flat cross-sectional concentration profile with uniform flow velocity across the channel is desired to achieve controlled and precise solute transport. This is often accommodated by the use of electroosmotic flow, however, it is not an ideal for many applications, particularly biomicrofluidics. Meanwhile, pressure-driven systems generally exhibit a parabolic cross-sectional concentration profile through a channel. We draw inspiration from finite element fluid dynamics simulations to design and fabricate a practical solution to achieving a flat solute concentration profile in a two-dimensional (2D) microfluidic channel. The channel possesses geometric features to passively flatten the solute profile before entering the defined region of interest in the microfluidic channel. An obviously flat solute profile across the channel is demonstrated in both simulation and experiment. This technology readily lends itself to many microfluidic applications which require controlled solute transport in pressure driven systems.

Matching Optimization of Impeller and Volute for Double-Channel with Double-Suction Pump

2014 ◽  
Vol 904 ◽  
pp. 311-314
Author(s):  
Bao Jie Luo ◽  
Lin Long Song ◽  
Pan Zhao
Keyword(s):  
Flow Characteristics ◽  
Prediction Method ◽  
Cross Sectional ◽  
Suction Pump ◽  
Uniform Distributions ◽  
Calculation Results ◽  
Tongue Position ◽  
Frequency Components ◽  
Suspended Matters ◽  
Double Channel

In order to study the matching optimization of the impeller and volute as well as the flow characteristics of double-channel with double-suction pump ,this paper based on CFD performance prediction method uses the same impeller to match the volute with different base diameters, guaranteeing the volute inlet width, flow cross-sectional area, and tongue position unchanged .The calculation results show that scheme A with the largest volute base diameter can not only achieve the excellent energy characteristics and the velocity-pressure uniform distributions, but also the exchange of the fluid energy is more sufficient in the volute. On one hand, a large clearance can not only make the movement interference intensity weaken between the impeller and volute, but also can decrease the high frequency components of the pressure pulsations .On the other hand, the big gap can maximum exert the pump effects to convey liquids containing solid suspended particles as well as the fibrous suspended matters. The research can not only provide some references to further study on matching optimization of the impeller and volute but also can contribute to the hydraulic design of the impeller and volute.

Micro-PIV Measurement on Transient Flows in Pneumatic MEMS Device for Cell Trapping

2011 ◽  
Author(s):  
Hyun Dong Kim ◽  
Kyung Chun Kim
Keyword(s):  
Flow Characteristics ◽  
Operational Conditions ◽  
Cell Trapping ◽  
Transient Flows ◽  
Micro Piv ◽  
Cell Chip ◽  
Piv Measurement ◽  
Measurement Results ◽  
Equilibrium Region ◽  
Pneumatic Vibrator

This paper presents a micro-PIV measurement for investigation of flow characteristics in a micro chamber for trapping of a live cell. The micro cell chip consisting of pneumatic vibrator arrays and a trap chamber was fabricated through a replica molding technology with a SU-8 mold and Polydimethylsiloxane (PDMS) polymer. The single cell in the trap chamber was manipulated and trapped in the equilibrium region by exploiting the geometrical symmetry of the vibrators. The x-axial velocity of the viscous fluid induced by the deformation of the flexible diaphragms was eliminated or minimized at the center of vibrators. From the measurement results, the proper operational conditions of the vibrators were determined and it is also verified that the particle can be actively manipulated and trapped as desired.

Sign in / Sign up

Export Citation Format

Share Document