scholarly journals Dynamics of photo-ablated carbon plasma in an inert gas atmosphere

1998 ◽  
Vol 16 (1) ◽  
pp. 31-38 ◽  
Author(s):  
T. Kerdja ◽  
S. Abdelli ◽  
E. H. Amara ◽  
D. Ghobrini ◽  
M. Si-Bachir ◽  
...  
Keyword(s):  
Wave Model ◽  
Inert Atmosphere ◽  
Viscous Drag ◽  
Laser Evaporation ◽  
Force Model ◽  
Plasma Dynamics ◽  
Gas Atmosphere ◽  
Viscous Drag Force ◽  
Swan Band ◽  
Two Stages

Time and space-resolved emission spectroscopy measurements were performed to investigate plasma dynamics during laser evaporation of a graphite target in an ambient inert atmosphere. Intense molecular emission is found to occur behind a front separating the plasma from the foreign gas. Two stages of expansion are found and are well described, using a viscous drag force model for the first one and a delayed ideal blast wave model for the second. The vibrational temperature estimated using the Swan band in helium at different pressures is presented.

The numerical study of viscous drag force influence on low-frequency surge motion of a semi-submersible in storm sea states

2020 ◽  
Vol 213 ◽  
pp. 107511 ◽  
Author(s):  
Shan Ma ◽  
De-kang Xu ◽  
Wen-yang Duan ◽  
Ji-kang Chen ◽  
Kang-ping Liao ◽  
...  
Keyword(s):  
Drag Force ◽  
Numerical Study ◽  
Low Frequency ◽  
Viscous Drag ◽  
Viscous Drag Force

Magnetic manipulation on the unlabeled nonmagnetic particles

2019 ◽  
Vol 33 (07) ◽  
pp. 1950047 ◽  
Author(s):  
Yongqing He ◽  
Laan Luo ◽  
Shuang Huang
Keyword(s):  
Flow Rate ◽  
Magnetic Force ◽  
Opposite Polarity ◽  
Viscous Drag ◽  
Maximum Deviation ◽  
Magnetic Manipulation ◽  
Practical Applications ◽  
Viscous Drag Force ◽  
Flow Rate Range ◽  
Nonmagnetic Particles

This paper reports two basic microfluidic strategies for the magnetic manipulation of unlabeled nonmagnetic particles/cells. One is the deflection induced by a single magnet, and the other is the confusing effect produced by two magnets of opposite polarity. They can be combined into more completed particle manipulations like continuous flow separation, counting and detection, which are essential steps in biomedical applications. We experimentally studied the dynamics of 10.4 and 20 [Formula: see text]m nonmagnetic polystyrene particles within a flow rate range of 30, 50, 70 and 90 [Formula: see text]L/min in a straight channel. We defined the cross-section length that the particles occupy as the “particle bandwidth” to characterize the extent of deflection and focusing. To predict the trajectories of the particles, we established a simple theoretical model by considering the magnetic force and viscous drag force. Compared with the experimental results, the maximum deviation of the simulation is 9.28%. The influences of magnetic nanoparticle concentration, magnetic field parameters, size of microparticles and flow rate are systematically investigated. We also demonstrated that the effective deflection and focusing could be realized at low Fe3O4 nanoparticle concentrations, which means that this method can reduce the damage on cells in the practical applications.

Computational Modeling of the Pulling Force in a Conventional Pultrusion Process

2013 ◽  
Vol 772 ◽  
pp. 399-406 ◽  
Author(s):  
Pierpaolo Carlone ◽  
Gaetano S. Palazzo
Keyword(s):  
Computational Modeling ◽  
Viscous Drag ◽  
Force Model ◽  
High Productivity ◽  
Pultrusion Process ◽  
Pulling Force ◽  
Frictional Effects

Pultrusion process is gaining increasing attention in several sectors, due to the high productivity and quality achievable. Recent researches highlighted the influence of the pulling force on the quality of pultruded products. In this paper a pulling force model, accounting for compacting, viscous, and frictional effects in a conventional pultrusion process has been implemented. The model is based on the combination of an impregnation, a thermochemical, and a frictional sub-models. Obtained outcomes evidenced, for the considered case,adominant role of the viscous drag.

scholarly journals Bacterial handling under the influence of non-uniform electric fields: dielectrophoretic and electrohydrodynamic effects

2008 ◽  
Vol 80 (4) ◽  
pp. 627-638 ◽  
Author(s):  
Flavio H. Fernádez-Morales ◽  
Julio E. Duarte ◽  
Josep Samitier-Martí
Keyword(s):  
Electric Fields ◽  
Microelectrode Array ◽  
Viscous Drag ◽  
Liquid Motion ◽  
Dielectrophoretic Force ◽  
Electrode Surfaces ◽  
Biological Objects ◽  
Viscous Drag Force ◽  
Lift Off ◽  
Positive Dielectrophoresis

This paper describes the modeling and experimental verification of a castellated microelectrode array intended tohandle biocells, based on common dielectrophoresis. The proposed microsystem was developed employing platinumelectrodes deposited by lift-off, silicon micromachining, and photoresin patterning techniques. Having fabricated the microdevice it was tested employing Escherichia coli as bioparticle model. Positive dielectrophoresis could be verified with the selected cells for frequencies above 100 kHz, and electrohydrodynamic effects were observed as the dominant phenomena when working at lower frequencies. As a result, negative dielectrophoresis could not be observed because its occurrence overlaps with electrohydrodynamic effects; i.e. the viscous drag force acting on the particles is greater than the dielectrophoretic force at frequencies where negative dielectrophoresis should occur. The experiments illustrate the convenience of this kind of microdevices to micro handling biological objects, opening the possibility for using these microarrays with other bioparticles. Additionally, liquid motion as a result of electrohydrodynamic effects must be taken into account when designing bioparticle micromanipulators, and could be used as mechanism to clean the electrode surfaces, that is one of the most important problems related to this kind of devices.

Particle Flow and Contamination in Slider Air Bearings for Hard Disk Drives

2003 ◽  
Vol 125 (2) ◽  
pp. 358-363 ◽  
Author(s):  
Xinjiang Shen ◽  
David B. Bogy
Keyword(s):  
Hard Disk Drives ◽  
Particle Flow ◽  
Viscous Drag ◽  
Air Bearing ◽  
Disk Drives ◽  
Air Bearings ◽  
Viscous Drag Force ◽  
Effect Of Particle Size ◽  
Pass Through ◽  
Particle Paths

For a particle entrained in an air bearing, various forces, such as the viscous drag force, Saffmann and Magnus lift forces and gravity force, will act on it. Such particles may pass through the air bearing or impact the slider or disk and then adhere to the surface or bounce off. In this paper, particle flow in an air bearing is simulated. The contamination of particles on a slider’s surface is analyzed using the assumption of adhesion upon impact. The effect of particle size and density on particle paths in the air bearing is studied. The numerical results show that particles are likely to contaminate slider surfaces in the transition regions on the rails. The density of the particles and the pitch angle of the slider are also found to strongly affect the flying path of the particles, and therefore, the accumulation of the particles on slider surfaces.

Shear StressTM Cleaning for Surface Departiculation

1987 ◽  
Vol 30 (1) ◽  
pp. 51-56
Author(s):  
Robert Musselman ◽  
Tom Yarbrough
Keyword(s):  
Shear Stress ◽  
Fluid Mechanics ◽  
High Velocity ◽  
Adhesion Force ◽  
Field Tests ◽  
Viscous Drag ◽  
Small Particles ◽  
Utility Industry ◽  
Liquid Spray ◽  
Viscous Drag Force

A cleaning technique widely used by the nuclear utility industry for removal of radioactive surface contamination has proven effective at removing non-hazardous contaminant particles as small as 0.1 micrometer (μm). The process employs a controlled high-velocity liquid spray inside a vapor containment enclosure to remove particles from a surface. The viscous drag force generated by the cleaning fluid applies a shear stress greater than the adhesion force that holds small particles to a substrate. Fluid mechanics and field tests indicate general cleaning parameters.

The dynamics of towed flexible cylinders Part 1. Neutrally buoyant elements

1988 ◽  
Vol 187 ◽  
pp. 507-532 ◽  
Author(s):  
A. P. Dowling
Keyword(s):  
Critical Point ◽  
Viscous Drag ◽  
Transverse Displacement ◽  
Flexible Cylinder ◽  
Low Frequencies ◽  
Viscous Forces ◽  
Transverse Vibrations ◽  
Crucial Effect ◽  
Viscous Drag Force ◽  
Neutrally Buoyant

The transverse vibrations of a thin, flexible cylinder under nominally constant towing conditions are investigated. The cylinder is neutrally buoyant, of radius aA with a free end and very small bending stiffness. As the cylinder is towed with velocity U, the tangential drag causes the tension in the cylinder to increase from zero at its free end to a maximum at the towing point. Transverse vibrations of the cylinder are opposed by a normal viscous drag force. Both the normal and tangential viscous forces can be described conveniently in terms of drag coefficients CN and CT. The ratio CN/CT has a crucial effect on the motion of the cylinder. The form of the transverse displacement is found to be greatly influenced by the existence of a critical point at which the effect of tension in the cylinder is cancelled by a fluid loading term. Matched asymptotic expansions are used to extend the solution across this critical point to apply the downstream boundary condition. Displacements well upstream of the critical point have a simple form, while nearer to the critical point the solution depends on whether the normal drag coefficient CN is greater or less than one-half CT.The typical acoustic streamer geometry considered is found to be stable to transverse displacements at all towing speeds. Forced perturbations of frequency ω are investigated. At low frequencies they propagate effectively along the cylinder with speed U. At higher frequencies they are attenuated.The effect of a rope drogue of length lR, radius aR is investigated. Provided ωlRaR/UaA is very small, the drogue has the same effect as a small increase in the length of the cylinder. However at higher frequencies and for small values of the ratio CN/CT attaching a drogue may be disadvantageous because it reduces the attenuation of high-frequency disturbances as they propagate down the cylinder.

Plasma Dynamics During Pulsed Laser Evaporation of High Tc Superconductors

1990 ◽  
Vol 201 ◽  
Author(s):  
Rajiv K. Singh ◽  
R. Neifeld ◽  
J. Narayan
Keyword(s):  
Theoretical Model ◽  
Energy Density ◽  
Excimer Laser ◽  
Pulsed Laser ◽  
Laser Wavelength ◽  
Laser Evaporation ◽  
Degree Of Ionization ◽  
Plasma Dynamics ◽  
Excimer Laser Irradiation

AbstractWe have theoretically and experimentally investigated the dynamics of the evaporated material generated by nanosecond excimer laser irradiation of YBa2Cu3O7 targets in vacuum. The velocity distribution and the ionization of the plasma were determined by the ion time of flight measurements. The excimer laser ablated species possessed very high velocities (> 106 cm/sec) which increased non-linearly with energy density. The ionization/ volume of the evaporated material exhibited a weak dependence on energy density, thereby suggesting the role of nonthermal mechanisms in the ionization process. These experimental results have been correlated with the theoretical model analyzing the plasma dynamics during pulsed laser evaporation of materials. A new modification to the earlier theoretical model is developed which accurately predicts the terminal velocities and the effect of ionization on these velocities. Various factors including, evaporation rates, degree of ionization, and laser wavelength which affect the plasma velocities will also be discussed.

DAMPING CHARACTERISTICS OF MR FLUIDS IN LOW MAGNETIC FIELDS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 829-836 ◽  
Author(s):  
HIDEYA NISHIYAMA ◽  
TADAMASA OYAMA ◽  
TOYOHISA FUJITA
Keyword(s):  
Magnetic Fields ◽  
Flat Plate ◽  
Phase Difference ◽  
Magnetic Fluid ◽  
Cluster Formation ◽  
Cluster Structure ◽  
Viscous Drag ◽  
Damping Characteristics ◽  
Mr Fluids ◽  
Viscous Drag Force

The cluster structure is visualized and the physical properties of new two types of nano MR fluids are measured in the applied magnetic fields. Correlating to these measurements, the damping characteristics of an oscillating flat plate immersed in two types of nano MR fluids such as damping amplitude, phase difference, viscous damping coefficient and viscous drag force acted on a flat plate are experimentally clarified, comparing with those of commercial magnetic fluid from the fluiddynamic points of view. It is shown that the resonance of damping amplitude and phase difference are very sensitive to the applied magnetic field, and further the damping effect of MR fluid is about ten times stronger than that of the commercial magnetic fluid even in low magnetic fields of 50–100 Gauss due to the robust cluster formation.

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