A Study for Flow Characteristics of Liquid Slip Flow in Rectangular Microchannels

2007 ◽  
Author(s):  
Jie Jiang ◽  
Yingli Hao ◽  
Jinli Lu
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Shear Rate ◽  
Water Flow ◽  
Slip Length ◽  
Velocity Slip ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Inlet Velocity ◽  
Friction Factors

Nowadays, there has been great interest in micro- and nano-applications. Understanding the flow and heat transfer in microscale is useful. The primary goal of this investigation is to reveal the flow behavior in microchannels. The deionized water flow in a microchannel was experimentally investigated. The pressure drops were measured under the conditions of different Reynolds numbers. The friction factors were obtained based on the experimental measurements. The friction factors deviate significantly from the conventional theory. A series of numerical simulation was also carried out to explore the mechanism of the deviation in the present paper. The numerical simulation adopting the slip boundary condition shows the numerical results coincide with the experimental results very well. The velocity slip was obtained based on the comparison with the experimental results. By introducing the slip length Ls, the velocity slip of water flow in the microchannel can be characterized. The velocity slip increases with the increase of the inlet velocity and the slip length increases with the increase of the shear rate. The linear Navier boundary condition breaks down when the shear rate reaches a critical value. A correlation between the velocity slip and the inlet velocity based on our experimental measurements and numerical results was obtained.

Slip Length Measurement of Water Flow on Graphite Surface Using Atomic Force Microscope

2014 ◽  
Vol 941-944 ◽  
pp. 1581-1584 ◽  
Author(s):  
Da Yong Li ◽  
Da Lei Jing ◽  
Yun Lu Pan ◽  
Khurshid Ahmad ◽  
Xue Zeng Zhao
Keyword(s):  
Atomic Force Microscope ◽  
Water Flow ◽  
Drag Force ◽  
Silicon Surface ◽  
Slip Length ◽  
Graphite Surface ◽  
Length Measurement ◽  
Hydrodynamic Drag ◽  
Experimental Measurements ◽  
Atomic Force

In this paper, we present experimental measurements of slip length of deionized (DI) water flow on a silicon surface and a graphite surface by using atomic force microscope. The results show that the measured hydrodynamic drag force is higher on silicon surface than that on graphite surface, and a measured slip length about 10 nm is obtained on the later surface.

Numerical Simulation of Pulsating Flow over Blood Vessel Robot

2012 ◽  
Vol 591-593 ◽  
pp. 1734-1738
Author(s):  
Chun Yan Huang ◽  
Fan Jiang
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Blood Flow ◽  
Blood Vessel ◽  
Surface Pressure ◽  
Blood Parameters ◽  
Pulsating Flow ◽  
Inlet Velocity ◽  
Blood Density

In order to study the influence of pulsating blood flow to robot and blood vessel, UDF programming of the inlet velocity is defined as the boundary condition, and the model simulate the turbulent blood flow. Moreover, in this situation, this paper analyzes the influence caused by blood parameters for the biggest surface pressure on robot. The results are showed that the variation of pressure and velocity is different on different position at 0.08s and 0.27s, and the surface pressure of the robot become greater by the increase of blood density or viscosity.

Examination of the Slip Boundary Condition by µ-PIV and Lattice Boltzmann Simulations

2002 ◽  
Author(s):  
Derek C. Tretheway ◽  
Luoding Zhu ◽  
Linda Petzold ◽  
Carl D. Meinhart
Keyword(s):  
Boundary Condition ◽  
Shear Rate ◽  
Channel Flow ◽  
Lattice Boltzmann ◽  
Slip Velocity ◽  
Slip Length ◽  
Slip Boundary Condition ◽  
Slip Boundary ◽  
Lattice Boltzmann Simulations ◽  
Bounce Back

This work examines the slip boundary condition by Lattice Boltzmann simulations, addresses the validity of the Navier’s hypothesis that the slip velocity is proportional to the shear rate and compares the Lattice Boltzmann simulations to the experimental results of Tretheway and Meinhart (Phys. of Fluids, 14, L9–L12). The numerical simulation models the boundary condition as the probability, P, of a particle to bounce-back relative to the probability of specular reflection, 1−P. For channel flow, the numerically calculated velocity profiles are consistent with the experimental profiles for both the no-slip and slip cases. No-slip is obtained for a probability of 100% bounce-back, while a probability of 0.03 is required to generate a slip length and slip velocity consistent with the experimental results of Tretheway and Meinhart for a hydrophobic surface. The simulations indicate that for microchannel flow the slip length is nearly constant along the channel walls, while the slip velocity varies with wall position as a results of variations in shear rate. Thus, the resulting velocity profile in a channel flow is more complex than a simple combination of the no-slip solution and slip velocity as is the case for flow between two infinite parallel plates.

scholarly journals Comparison between analytical, numerical, and experimental results of grouping effects in droplet streams

2017 ◽  
Author(s):  
Norbert Roth ◽  
Hassan Gomaa ◽  
Alon Livne ◽  
David Katoshevski ◽  
Bernhard Weigand
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Direct Numerical Simulation ◽  
Initial Boundary ◽  
Experimental Results ◽  
Controllable System ◽  
Initial Boundary Condition ◽  
Linear Behaviour ◽  
Monodisperse Droplet ◽  
Monodisperse Droplets

Grouping of droplets was studied in monodisperse droplet streams. This very controllable system allows to studybasic effects. In experiments droplet streams with monodisperse droplets were generated, however, with initially two different inter droplet spacing. A larger inter droplet spacing is followed by a little bit smaller one, which is followed by a larger one and so on. Due to this initial boundary condition groups of two droplets form, which approach each other and finally coagulate. It was found, that the velocity of the droplet approach is linearly dependent on the spacing between the droplets. This process was simulated by direct numerical simulation using the in-house code FS3D. The results of the simulations show the  ame linear behaviour. For larger computational domains thenumerical results approach the experimental results.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4685

Hydrodynamic slippage of water at surfaces

2017 ◽  
Author(s):  
E. Charlaix ◽  
L. Bocquet
Keyword(s):  
Boundary Condition ◽  
Molecular Mechanisms ◽  
Slip Length ◽  
Molecular Simulations ◽  
Short Review ◽  
Solid Surfaces ◽  
Experimental Investigations

The boundary condition (B.C.) for hydrodynamic flows at solid surfaces is usually assumed to be that of no slip. However a number of molecular simulations and experimental investigations over the last two decades have demonstrated violations of the no-slip B.C., leading to hydrodynamic slippage at solid surfaces. In this short review, we explore the molecular mechanisms leading to hydrodynamic slippage of water at various surfaces and discuss experimental investigations allowing us to measure the so-called slip length

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

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