Research of bubble flow characteristics in microfluidic chip

2017 ◽  
Vol 31 (10) ◽  
pp. 1750109
Author(s):  
Chao Qiu ◽  
Han Cheng ◽  
Shuxian Chen
Keyword(s):  
Heat Flux ◽  
Microfluidic Chip ◽  
High Speed ◽  
Flow Characteristics ◽  
Hydrophobic Surface ◽  
High Speed Photography ◽  
Bubble Flow ◽  
Hydrophilic Surface ◽  
Biological Detection ◽  
Speed Up

Bubble is the heart of the microfluidic chip, which takes a significant role in drug release, biological detection and so on. In this case, bubble flow characteristics in microfluidic chip are the key to realize its function. In this paper, bubble flow characteristics in the microfluidic chip have been studied with high speed photography system by controlling the wettability and the heat flux of the microelectrode surface. The result shows that bubble flows faster on the electrode with hydrophobic surface. In addition, loading current to the electrode with hydrophilic surface could also speed up the movement of bubble, and the flow rate of bubble increases with the increasing heat flux of the electrode.

Flow Characteristics of Rectangular Liquid Jets Injected Into Low Subsonic Crossflow

2019 ◽  
Author(s):  
M. Tadjfar ◽  
A. Jaberi ◽  
R. Shokri
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Combustion Efficiency ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Aspect Ratios ◽  
Jet Trajectory ◽  
Wide Range ◽  
Circular Holes ◽  
Subsonic Crossflow

Abstract Perpendicular injection of liquid jets into gaseous crossflow is well-known as an effective way to obtain good mixing between liquid fuel and air crossflow. Mostly, injectors with circular holes were used as the standard method of fuel spraying. However, recently a great attention to injectors with non-circular holes has emerged that aims to improve the quality of fuel mixing and consequently combustion efficiency. In the present work, rectangular injectors with different aspect ratios varying from 1 to 4 were experimentally studied. Using a wind tunnel with maximum air velocity of 42 m/s, tests were performed for a wide range of flow conditions including liquid-to-air momentum ratios of 10, 20, 30 and 40. Backlight shadowgraphy and high speed photography were employed to capture the instantaneous physics of the liquid jets discharged into gaseous crossflow. The flow physics of the rectangular liquid jets were investigated by means of flow visualizations. Different regimes of flow breakup including capillary, arcade, bag and multimode were observed for rectangular jets. Moreover, a new technique was used to calculate the trajectory of the liquid jets. It was shown the nozzle’s shape has no significant effect on jet trajectory. Also, the momentum ratio was found to has a profound effect on jet trajectory.

Experimental and Numerical Study of Hydrodynamic Cavitation of Orifice Plates with Multiple Triangular Holes

2012 ◽  
Vol 256-259 ◽  
pp. 2519-2522 ◽  
Author(s):  
Zhi Yong Dong ◽  
Qi Qi Chen ◽  
Yong Gang Yang ◽  
Bin Shi
Keyword(s):  
Velocity Profile ◽  
High Speed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Orifice Plate ◽  
Hydrodynamic Cavitation ◽  
High Speed Photography ◽  
Hydraulic Characteristics ◽  
Image Velocimetry

Hydraulic characteristics of orifice plates with multiple triangular holes in hydrodynamic cavitation reactor were experimentally investigated by use of three dimensional particle image velocimetry (PIV), high speed photography, electronic multi-pressure scanivalve and pressure data acquisition system, and numerically simulated by CFD software Flow 3D in this paper. Effects of number, arrangement and ratio of holes on hydraulic characteristics of the orifice plates were considered. Effects of arrangement and ratio of holes and flow velocity ahead of plate on cavitation number and velocity profile were compared. Distribution of turbulent kinetic energy and similarity of velocity profile were analyzed. And characteristics of cavitating flow downstream of the orifice plate were photographically observed by high speed camera. Also, a comparison with flow characteristics of orifice plate with hybrid holes (circle, square and triangle) was made.

scholarly journals Influence of Discharge Gap On Material Removal and Melt Pool Movement in EDM Discharge Process

2021 ◽  
Author(s):  
Xiaoming Yue ◽  
Ji Fan ◽  
Qi Li ◽  
Xiaodong Yang ◽  
Zuoke Xu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Material Removal ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
External Pressure ◽  
High Speed Photography ◽  
Discharge Process ◽  
Melt Pool ◽  
Discharge Gap ◽  
Gap Width

Abstract In electrical discharge machining (EDM), gap control is the key to stable processing; the discharge gap plays a significant role in EDM. To determine the influence of the discharge gap on material removal and melt pool movement, which are two fundamental issues in EDM, high-speed photography and molecular dynamics (MD) simulations were used to study the discharge process. Research results demonstrate that the discharge gap has a significant influence on material removal during the discharge process. A smaller gap width produces more and larger removed materials. The influence mechanism of the gap width on material removal is explained as follows. A smaller gap width produces discharge plasma with a smaller diameter and greater heat flux. Discharge with a greater heat flux generates more material removed during the discharge process. In addition, a smaller gap width and greater heat flux produce a stronger interaction of metal vapor jets, generating a stronger shear force acting on the melt pool. The discharge gap also influences the movement of the melt pool and the final topography of the discharge crater through external pressure acting on the melt pool. Smaller gap width produces greater external pressure acting on the melt pool, generating a bowl-shaped melt pool and a discharge crater with a depression in the center and a bulge around the edge. A larger gap width produces less external pressure acting on the melt pool, generating a flat melt pool and a discharge crater with swelling in the center and a depression around the edge.

Thermal-Fluid Phenomena Induced by Nanosecond-Pulse Heating of Materials in Water

2001 ◽  
Vol 123 (6) ◽  
pp. 1123-1132 ◽  
Author(s):  
I. Ueno ◽  
M. Shoji
Keyword(s):  
High Speed ◽  
Bubble Formation ◽  
Water System ◽  
Solid Material ◽  
Laser Wavelength ◽  
High Speed Photography ◽  
Time Resolved ◽  
Pump And Probe ◽  
Shock Wave Generation ◽  
Speed Up

Thermal-hydraulic phenomena adjacent to the liquid metal-water and solid material-water interfaces induced by nanosecond pulsed Nd:YAG laser (wavelength: 532 nm, FWHM: ∼13 ns) heating with the fluence F of 5.0×101∼1.0×103 mJ/cm2 were experimentally investigated. By applying the high-speed photography with a frame speed up to 2.0×107 fps, the aspects of the bubble formation, shock wave generation and propagation were observed. The bubble formation on the heated material’s surface of about 80 nm in diameter was detected in Si-water system from the time-resolved reflection (TRR) signal by applying the pump and probe method.

STUDY OF LEIDENFROST MECHANISM IN DROPLET IMPACTING ON HYDROPHILIC AND HYDROPHOBIC SURFACES

2013 ◽  
Vol 21 (04) ◽  
pp. 1350028 ◽  
Author(s):  
SEOL HA KIM ◽  
JUN YOUNG KANG ◽  
HO SEON AHN ◽  
HANG JIN JO ◽  
MOO HWAN KIM
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Hydrophobic Surface ◽  
Bubble Nucleation ◽  
Hydrophilic Surface ◽  
Water Droplets ◽  
Time Resolved ◽  
Droplet Dynamics ◽  
Different Shapes ◽  
Time Resolved Imaging

Water droplets, 2 mm in diameter, were allowed to fall freely onto hydrophobic and hydrophilic heated surfaces, and their impacts were imaged using high-speed cameras to investigate the droplet dynamics and heat transfer. As the heating power increased, the water droplets evaporated faster, eventually hovering over the surface due to the formation of a boiling film when the Leidenfrost point (LFP) was reached. The heat transfer from the surface into the droplet was evaluated, and LFP transition phenomena were investigated using time-resolved imaging of both side and bottom views. The hydrophilic surface showed a higher heat transfer rate and a higher LFP than the hydrophobic surface did. Furthermore, the droplet dynamics revealed very different shapes depending on the surface wettability; vigorous bubble nucleation and growth was observable for the hydrophilic surface, but not the hydrophobic surface. The rebound behavior of the droplets was analyzed based on the droplet free energy, including kinetic, potential, and surface energy terms.

Bubble Ebullition on a Hydrophilic Surface

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Aritra Sur ◽  
Yi Lu ◽  
Carmen Pascente ◽  
Paul Ruchhoeft
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Working Fluid ◽  
Hydrophilic Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Nucleate Bubble

Nucleate boiling heat transfer depends on various aspects of the bubble ebullition, such as the bubble nucleation, growth and departure. In this work, a synchronized high-speed optical imaging and infrared (IR) thermography approach was employed to study the ebullition process of a single bubble on a hydrophilic surface. The boiling experiments were conducted at saturated temperature and atmospheric pressure conditions. De-ionized (DI) water was used as the working fluid. The boiling device was made of a 385-um thick silicon wafer. A thin film heater was deposited on one side, and the other side was used as the boiling surface. The onset of nucleate boiling (ONB) occurs at a wall superheat of ΔTsup= 12 °C and an applied heat flux of q" = 35.9 kW/m2. The evolution of the wall heat flux distribution was obtained from the IR temperature measurements, which clearly depicts the existence of the microlayer near the three-phase contact line of the nucleate bubble. The results suggest that, during the bubble growth stage, the evaporation in the microlayer region contributes dominantly to the nucleate boiling heat transfer; however, once the bubble starts to depart from the boiling surface, the microlayer quickly vanishes, and the transient conduction and the microconvection become the prevailing heat transfer mechanisms.

Impacts of Circular Liquid Jet Injection Angle Into Low Subsonic Crossflow

2021 ◽  
Author(s):  
Si. Kasmaiee ◽  
M. Tadjfar ◽  
Sa. Kasmaiee
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Liquid Jet ◽  
High Speed Photography ◽  
Interfacial Instabilities ◽  
Injection Angle ◽  
Circular Nozzle ◽  
Subsonic Crossflow ◽  
Working Liquid

Abstract One of the most common ways to obtain mixing between liquid and air, is by injecting the liquid jet into an incoming gaseous crossflow. The physics of this mixing flow is very complicated due to the presence of many flow interfacial instabilities. Usually, a perpendicular liquid jet into the cross flow airstream is used as the standard method of mixing. In the present work, the effect of the injection angle of the liquid flow emanated from a circular nozzle into airstream was experimentally investigated. The flow characteristics of the liquid jet were visualized by diffused backlight shadowgraph technique and high-speed photography. Water was used as the working liquid and tests were conducted into an incoming airstream at room temperature and pressure. A circular nozzle with 1.5 mm in diameter was used. The injection angles of the 30, 45, 60 and 90 degrees of the liquid jet into the airstream were considered. Different parameters of liquid jet flow such as breakup length and trajectory were measured. It was found that at low angles the path was independent from the momentum ratio.

Experimental study on water entry of cylindrical projectiles with different nose shapes

2019 ◽  
Vol 33 (09) ◽  
pp. 1950107 ◽  
Author(s):  
Guo-Xin Yan ◽  
Guang Pan ◽  
Yao Shi ◽  
Guan-Hua Wang
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Cavity Flow ◽  
Water Entry ◽  
High Speed Photography ◽  
Entry Angle ◽  
Entry Velocity ◽  
Nose Shape ◽  
Cavity Evolution ◽  
Trajectory Stability

Water entry experiments of projectiles with different nose shapes were performed under different entry angles and velocities using high-speed photography technology. The cavity flow characteristics of the near water surface, including splash jet, splash crown, surface seal of cavity, pull away, deep seal of cavity and cavity collapses, were systematically investigated using a high-speed camera. The emphasis of the study is paid on the effect of nose shape, water entry angle and velocity on the evolution of the air entraining cavity. The experimental results demonstrate that the nose shape of projectile has a significant influence on the jet flow, the cavity diameter and trajectory stability in the case of certain other conditions. On the other hand, the splash scale, cavity diameter increase gradually with the increasing of the water entry velocity, as well as the cavitation closed in advance. Furthermore, the water entry angle of the projectile plays an important role in the cavity evolution and the close type.

A Comprehensive Model for Nucleate Pool Boiling Heat Transfer Including Microlayer Evaporation

1976 ◽  
Vol 98 (4) ◽  
pp. 623-629 ◽  
Author(s):  
R. L. Judd ◽  
K. S. Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Speed ◽  
Methylene Chloride ◽  
Significant Proportion ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Evaporation Heat ◽  
Microlayer Evaporation

The results of an experimental investigation are presented in which dichloromethane (methylene chloride) boiling on a glass surface was studied using laser interferometry and high-speed photography. New data for active site density, frequency of bubble emission, and bubble departure radius were obtained in conjunction with measurements of the volume of microlayer evaporated from the film underlying the base of each bubble for various combinations of heat flux and subcooling. These results were used to support a model for predicting boiling heat flux incorporating microlayer evaporation, natural convection, and nucleate boiling mechanisms. Microlayer evaporation heat transfer is shown to represent a significant proportion of the total heat transfer for the range of heat flux and sub-cooling investigated.

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