On the pressure gradient boundary condition for the contact of two biphasic cartilage layers

The problem of peristaltic nanofluid flow in an asymmetric channel in the presence of the second-order slip boundary condition was investigated in this paper. To the best of the authors’ knowledge, this parameter was here incorporated for the first time in such field of a peristaltic flow. The system governing the current flow was found as a set of nonlinear partial differential equations in the stream function, pressure gradient, nanoparticle concentration, and temperature distribution. Therefore, this system has been successfully solved exactly via a very effective procedure. These exact solutions were then proved to reduce to well-known results in the absence of second slip which were published very recently in the literature. Effect of the second slip parameter on the present physical parameters was discussed through graphs and it was found that this type of slip is a very important one to predict the investigated physical model. Moreover, the variation of many physical parameters such as amplitudes of the lower and upper waves, phase difference on the temperature distribution, nanoparticle concentration, pressure rise, velocity, and pressure gradient were also discussed. Finally, the present results may be viewed as an optimal choice for their dependence on the exact solutions which are obtained due to the highly complex nonlinear system.

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Uncertainty of PIV/PTV based pressure, using velocity uncertainty

14th International Symposium on Particle Image Velocimetry ◽

10.18409/ispiv.v1i1.148 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Jiacheng Zhang ◽

Sayantan Bhattacharya ◽

Pavlos Vlachos

Keyword(s):

Boundary Condition ◽

Pressure Gradient ◽

Velocity Measurement ◽

Pressure Field ◽

Uncertainty Estimation ◽

Linear Transformations ◽

Reconstruction Process ◽

Pressure Fields ◽

Pressure Boundary Condition ◽

Instantaneous Pressure

Pressure reconstruction from velocity measurements using particle image velocimetry (PIV) and particle tracking velocimetry (PTV) has drawn significant attention as it can provide instantaneous pressure fields without altering the flow. Previous studies have found that the accuracy of the calcualted pressure field depends on several factors including the accuarcy of the velocity measurement, the spatiotemporal resolutions, the method for calculating pressure-gradient, the algorithm for pressure-gradient integration, the pressure boundary condition, etc. Therefore, it is critical and challenging to quantify the uncertainty of the reconstructed pressure field. The recent development of the uncertainty quantification algorithms for PIV and PTV allows for the local and instantaneous uncertainty estimation of velocity measurement, which can be used to infer the pressure uncertainty. In this study, we introduce a framework that propagates the standard velocity uncertainty defined as the standard deviation of the velocity error distribution through the pressure reconstruction process to obtain the uncertainty of the pressure field. The uncertainty propagations through the calculation of the pressure-gradient and the pressure-gradient integration were modeled as linear transformations, which can reproduce the effects of the spatiotemporal resolutions, the numerical schemes, the integration algorithms, and the pressure boundary condition on the accuracy of the resulting pressure fields. The proposed uncertainty estimation approach also considers the effect of the spatiotemporal and componentwise correlation of the velocity errors in common PIV/PTV measurements on the pressure uncertainty.

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Simulation of Effective Slip and Drag in Pressure-Driven Flow on Superhydrophobic Surfaces

Journal of Nanomaterials ◽

10.1155/2016/5052602 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Yuanding Huang ◽

Xuezeng Zhao ◽

Yunlu Pan ◽

Khurshid Ahmad

Keyword(s):

Boundary Condition ◽

Pressure Gradient ◽

Flow Rate ◽

Slip Boundary Condition ◽

Liquid Interface ◽

Driving Pressure ◽

Superhydrophobic Surfaces ◽

Boundary Slip ◽

Obvious Effect ◽

Effective Slip

The flow on superhydrophobic surfaces was investigated using finite element modeling (FEM). Surfaces with different textures like grooves, square pillars, and cylinders immersed in liquid forming Cassie state were modeled. Nonslip boundary condition was assumed at solid-liquid interface while slip boundary condition was supposed at gas-liquid interface. It was found that the flow rate can be affected by the shape of the texture, the fraction of the gas-liquid area, the height of the channel, and the driving pressure gradient. By extracting the effective boundary slip from the flow rate based on a model, it was found that the shape of the textures and the fraction of the gas-liquid area affect the effective slip significantly while the height of the channel and the driving pressure gradient have no obvious effect on effective slip.

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Activated Prominences; Mechanisms for Activation and Eruption

International Astronomical Union Colloquium ◽

10.1017/s0252921100065714 ◽

1979 ◽

Vol 44 ◽

pp. 307-313

Author(s):

D.S. Spicer

Keyword(s):

Pressure Gradient ◽

Density Gradient ◽

Current Density ◽

Convective Instability ◽

Tearing Mode ◽

Magnetic Shear ◽

Long Wavelength ◽

Ideal Mhd ◽

Gradient Change ◽

Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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An Attack on the Contamination Problem in the Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061859 ◽

1967 ◽

Vol 25 ◽

pp. 368-368

Author(s):

J. J. Kelsch ◽

A. Holtz

Keyword(s):

Electron Microscope ◽

Pressure Gradient ◽

Ionization Potential ◽

Simple Solution ◽

Specimen Surface ◽

Contamination Rate ◽

Local Pressure ◽

High Ionization ◽

Hydrocarbon Molecules ◽

Contamination Problem

A simple solution to the serious problem of specimen contamination in the electron microscope is presented. This is accomplished by the introduction of clean helium into the vacuum exactly at the specimen position. The local pressure gradient thus established inhibits the migration of hydrocarbon molecules to the specimen surface. The high ionization potential of He permits the use of relatively large volumes of the gas, without interfering with gun stability. The contamination rate is reduced on metal samples by a factor of 10.

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Hydration Chamber for Jeolco 200 Kv Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069703 ◽

1970 ◽

Vol 28 ◽

pp. 542-543

Author(s):

V. R. Matricardi ◽

G. G. Hausner ◽

D. F. Parsons

Keyword(s):

Electron Microscope ◽

Water Vapor ◽

Vapor Pressure ◽

Pressure Gradient ◽

Room Temperature ◽

List Type ◽

Type Number ◽

Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

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