Prediction of Gas Flow Through Short and Long 2-D Micro and Nano-Channels Using a Generalized Slip Model

2008 ◽  
Author(s):  
M. Raisee ◽  
N. Vahedi ◽  
A. Rostamzadeh
Keyword(s):  
Gas Flow ◽  
Spectral Element Method ◽  
Slip Flow ◽  
Spectral Element ◽  
Pressure Variation ◽  
Numerical Results ◽  
Recent Effort ◽  
Slip Model ◽  
Nitrogen Flow ◽  
Flow Through

This paper reports the outcome of our recent effort in prediction of gas slip flow through microchannels. Slip Nitrogen flow through short (L/h = 20) and long (L/h = 2500) microchannels is analyzed and discussed using spectral element method and the generalize slip model boundary condition of Karniadakis and Beskok [1]. The well-known curvature in pressure distribution, due to the compressible behavior of the gas flow, is observed. Comparison of numerical results (for density and pressure variation as well as the slip velocity distribution with the experimental and DSMC data as well as reported numerical results showed that the generalize slip model is able to produce reliable results for both short and long microchannels.

Applicability of 3D Spectral Element Method for Computing Close-Range Underwater Piling Noises

2019 ◽  
Vol 27 (04) ◽  
pp. 1950012
Author(s):  
C. Jeong ◽  
A. Manalaysay ◽  
H. N. Gharti ◽  
S. Guan ◽  
J. Vignola
Keyword(s):  
Shear Wave ◽  
Spectral Element Method ◽  
Spectral Element ◽  
Numerical Results ◽  
Pile Driving ◽  
Underwater Noise ◽  
Close Range ◽  
Mach Cones ◽  
Axially Asymmetric ◽  
Element Method

Pile driving is used for constructing foundation supports for offshore structures. Underwater noise, induced by in-water pile driving, could adversely impact marine life near the piling location. Many studies have computed this noise in close ranges by using semi-analytical models and Finite Element Method (FEM) models. This work presents a Spectral Element Method (SEM) wave simulator as an alternative simulation tool to obtain close-range underwater piling noise in complex, fully three-dimensional, axially-asymmetric settings in the time domain for impacting force signals with high-frequency contents (e.g., frequencies greater than 1000[Formula: see text]Hz). The presented numerical results show that the flexibility of SEM can accommodate the axially-asymmetric geometry of a model, its heterogeneity, and fluid-solid coupling. We showed that there are multiple Mach Cones of different angles in fluid and sediment caused by the difference in wave speeds in fluid, a pile, and sediment. The angles of Mach Cones in our numerical results match those that are theoretically evaluated. A previous work18 had shown that Mach Cone waves lead to intense amplitudes of underwater piling noise via a FEM simulation in an axis-symmetric setting. Since it modeled sediment as fluid with a larger wave speed than that of water, we examined if our SEM simulation, using solid sediment–fluid coupling, leads to additional Mach Cones. Because this work computes the shear wave in sediment and the downward-propagating shear wave in a pile, we present six Mach Cones in fluid and sediment induced by downward-propagating P- and S-waves in a pile in lieu of two previously-reported Mach Cones in fluid and sediment (modeled as fluid) induced by a downward-propagating P-wave in a pile. We also showed that the amplitudes of the close-range underwater noise are dependent on the cross-sectional geometry of a pile. In addition, when a pile is surrounded by a solid of an axially-asymmetric geometry, waves are reflected from the surface of the surrounding solid back to the fluid so that constructive and destructive interferences of waves take place in the fluid and affect the amplitude of the underwater piling noise.

Liquid Leak Predictions in Micro- and Nanoporous Gaskets

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Lotfi Grine ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Stokes Equations ◽  
Slip Flow ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Experimental Conditions ◽  
Navier Stokes Equations ◽  
Slip Boundary ◽  
Gas Leak ◽  
Flow Through

In recent years, quite few experimental and theoretical studies have been conducted to predict gas leak rate through gaskets. However, a very limited work is done on liquid leak rates through gaskets. The slip flow model is used to predict liquid flow through porous gaskets based on measurements of gas flow at different pressures. In fact, an extrapolation of the porosity parameter approach (Grine, L., and Bouzid, A., 2009, “Correlation of Gaseous Mass Leak Rates Through Micro and Nano-Porous Gaskets,” ASME Paper No. PVP2009-77205) used to correlate leak rates between different gases is used to predict liquid leak rates. In the present article, an analytical-computational methodology based on the number and pore size to predict liquid micro- and nanoflows in the slip flow regime through gaskets is presented. The formulation is based on the Navier–Stokes equations associated with slip boundary condition at the wall. The mass leak rates through a gasket considered as a porous media under various experimental conditions of fluid media, pressure, and gasket stress were conducted on a special gasket test rig. Gaseous and liquid leaks are measured and comparisons with the analytical predictions are made.

scholarly journals A Numerical Study on Gas Flow through Anisotropic Sierpinski Carpet with Slippage Effect

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shuxia Qiu ◽  
Lipei Zhang ◽  
Zhenhua Tian ◽  
Zhouting Jiang ◽  
Mo Yang ◽  
...  
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Gas Flow ◽  
Gas Permeability ◽  
Fractal Model ◽  
Numerical Results ◽  
Pore Scale ◽  
Gas Slippage ◽  
Slippage Effect ◽  
Flow Through

A pore-scale model has been developed to study the gas flow through multiscale porous media based on a two-dimensional self-similar Sierpinski carpet. The permeability tensor with slippage effect is proposed, and the effects of complex configurations on gas permeability have been discussed. The present fractal model has been validated by comparison with theoretical models and available experimental data. The numerical results show that the flow field and permeability of the anisotropic Sierpinski model are different from that of the isotropic model, and the anisotropy of porous media can enhance gas permeability. The gas permeability of porous media increases with the increment of porosity, while it decreases with increased pore fractal dimension under fixed porosity. Furthermore, the gas slippage effect strengthens as the pore fractal dimension decreases. However, the relationship between the gas slippage effect and porosity is a nonmonotonic decreasing function because reduced pore size and enhanced flow resistance may be simultaneously involved with decreasing porosity. The proposed pore-scale fractal model can present insights on characterizing complex and multiscale structures of porous media and understanding gas flow mechanisms. The numerical results may provide useful guidelines for the applications of porous materials in oil and gas engineering, hydraulic engineering, chemical engineering, thermal power engineering, food engineering, etc.

A Criterion for the Experimental Validation of the Slip-Flow Models for Incompressible Rarefied Gases Through Microchannels

2004 ◽  
Author(s):  
G. L. Morini ◽  
M. Lorenzini ◽  
M. Spiga
Keyword(s):  
Friction Factor ◽  
Cross Section ◽  
Gas Flow ◽  
Experimental Validation ◽  
Rarefied Gas ◽  
Slip Flow ◽  
Rarefied Gas Flow ◽  
Flow Models ◽  
Flow Through ◽  
Rarefaction Effects

This paper is devoted to analyzing the friction factor of incompressible rarefied gas flow through microchannels. A theoretical investigation is conducted in order to underline the conditions for experimentally evidencing rarefaction effects on the pressure drop. It is demonstrated that for a fixed geometry of the microchannel cross section it is possible to calculate the minimum value of the Knudsen number for which the rarefaction effects can be observed experimentally, taking into account the experimental uncertainties on the evaluation of the friction factor.

Gas Flow Through Trapezoidal Microgaps

1973 ◽  
Vol 95 (1) ◽  
pp. 52-58
Author(s):  
W. G. Rieder ◽  
D. R. Haworth
Keyword(s):  
Gas Flow ◽  
Slip Flow ◽  
Circular Cross Section ◽  
Velocity Profiles ◽  
Transition Regime ◽  
Flow Rates ◽  
Flow Through ◽  
Value Flow ◽  
Made In

A generalized approach based on a model of the Boltzmann equation is suggested for predicting velocity profiles and gas flow rates through trapezoidal microgaps. Sample results are given for selected trapezoidal, rectangular, square, and circular cross section passages for Knudsen numbers ranging from 0.1 to about 10. Comparison of predicted flow rates for rectangular passages with available empirical data seems to indicate that where passage size is characterized by a single dimension, a simple across-channel measurement is inappropriate. While relative velocity profiles are independent of this value, flow rates are not. Accuracy of predictions may be enhanced by matching with analytical or empirical results for similar geometries of larger size. A flow rate from the low Knudsen number end of the transition regime is matched with one from the overlapping region of the slip-flow regime and an arbitrary adjustment is made in the characterization of passage size. This adjustment can then be incorporated into the results throughout the transition regime.

Large Eddy Simulation of Gasoline Sprays in a Lagrangian-Eulerian Framework Using the High-Order Spectral Element Method

2021 ◽  
Author(s):  
Juan D. Colmenares F. ◽  
Muhsin M. Ameen ◽  
Saumil S. Patel
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Gas Flow ◽  
Spectral Element Method ◽  
Cone Angle ◽  
Spectral Element ◽  
High Order ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Element Method

Abstract Predicting the spray evolution using simulations requires accurate modeling of the turbulent gas-phase flow field. In this study, the high-order spectral-element method (SEM), implemented in the code Nek5000, was used to provide highly-resolved solutions to the turbulent flow field. Spray modeling capabilities were implemented into the Nek5000 code. The spray is modeled in a Lagrangian-Eulerian (LE) framework, where the liquid is represented by discrete parcels of droplets. The method for coupling liquid and gas in the context of SEM is described, which allows for very fine meshes to be used without affecting the stability of the solution. Large-eddy simulations (LES) of the eight-hole ECN Spray G gasoline injector were conducted. Numerical results are compared against experimental data for liquid penetration, droplet size and gas velocity. The morphology of the multi-plume spray is compared against experimental data. The effect of different spray injection inputs is analyzed. It was found that using a plume direction of 33° and an injection cone angle of 30° produced the best results overall. This work shows the applicability of SEM for spray modeling applications, where use of a high-order flow solver can help us understand the multi-plume spray aerodynamics and how it leads to plume collapse under certain conditions. Results also highlight the need for tuning spray input parameters in the LE framework, even when high-fidelity gas flow solutions are possible.

Simulation of borehole acoustic wavefields in fractured media by combining the spectral element method and linear-slip model

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Jiaqi Xu ◽  
Qing Huo Liu ◽  
Hengshan Hu ◽  
Yang Zhong
Keyword(s):  
Finite Difference ◽  
Tilt Angle ◽  
Spectral Element Method ◽  
Numerical Solutions ◽  
Spectral Element ◽  
Fractured Media ◽  
Dipole Source ◽  
Slip Model ◽  
Linear Slip Model ◽  
Element Method

We use the spectral element method (SEM) to simulate 3D acoustic wavefields in the fluid-filled borehole embedded in the fractured media. The fractures are characterized by the linear-slip model (LSM), which is incorporated into the surface integral of the SEM weak form, avoiding meshing individual fractures, thus reducing the degrees of freedom of the fractures comparing with meshing each fracture directly. For the fracture-free case, we validate SEM through the comparison with the real-axis integration (RAI) method for both monopole and dipole sources. For the case with a fracture, we compare the SEM-LSM solutions with the reference numerical solutions of a thin layer model using finite-difference method. Good agreement is achieved between the results from the proposed method and the reference finite-difference solutions. We find that the acoustic wavefields excited by a dipole source are more sensitive to the fractures than those by a monopole source. To show the ability of the approach to handle complex problems, we simulate the cases with a tilted fracture and multiple fractures. Based on the simulated results, we investigate the influence of the fracture parameters (e.g., stiffness, tilt angle, azimuth, thickness, number and spatial intervals of fractures) on the scattered wavefields. We find that the tilt angle has an obvious influence on the scattered waveforms and amplitudes. The results also demonstrate that the wavefields are quite sensitive to the number of fractures. The magnitudes of the horizontal-components transmitted wavefields decrease linearly with the number of the fractures. Through analyzing the synthetic data in time and frequency domains, we discuss how to evaluate the properties of fractures intersected by a borehole.

Experimental investigation of rarefied gas flow in different channels

1974 ◽  
Vol 64 (3) ◽  
pp. 417-438 ◽  
Author(s):  
B. T. Porodnov ◽  
P. E. Suetin ◽  
S. F. Borisov ◽  
V. D. Akinshin
Keyword(s):  
Experimental Investigation ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Slip Flow ◽  
Molecular Scattering ◽  
Highly Sensitive ◽  
Accommodation Coefficients ◽  
Tangential Momentum ◽  
Flow Through ◽  
Made In

An experimental investigation of flows of a large number of inert and polyatomic gases in various channels, a non-ideal orifice, flat slits with different surface roughnesses and wall materials, capillary packets with molten walls and a capillary sieve, has been made.The unsteady flow method and a highly sensitive capacitance micromanometer were used (the sensitivity being ∼ 3 × 10−4N/m2Hz). Measurements were made in a range of Knudsen numbers 5 × 104–10−3at ∼ 293 °K, and some measurements for flow through a non-ideal orifice were carried out at 77.2°K.It was found that, both in the viscous slip-flow and free-molecule regimes for the channels with molten walls, the experimental conductivities were higher (by ∼ 15%) than theoretical ones calculated assuming diffuse molecular scattering by the walls. We have also observed that the channel conductivity essentially depends on the channel surface roughness and on the kind of gas. The larger the roughness height, the lower the conductivity. From the experimental data the tangential momentum accommodation coefficients were calculated.

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