scholarly journals A Simple Analytical Model for Estimating the Dissolution-Driven Instability in a Porous Medium

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 60
Author(s):  
Layachi Hadji
Keyword(s):  
Stability Problem ◽  
Three Dimensional ◽  
Step Function ◽  
New Approach ◽  
Engineering Mathematics ◽  
Alternative Approach ◽  
Function Base ◽  
The Stability ◽  
Rayleigh Benard ◽  
Profile Approach

This article deals with the stability problem that arises in the modeling of the geological sequestration of carbon dioxide. It provides a more detailed description of the alternative approach to tackling the stability problem put forth by Vo and Hadji (Physics of Fluids, 2017, 29, 127101) and Wanstall and Hadji (Journal of Engineering Mathematics, 2018, 108, 53–71), and it extends two-dimensional analysis to the three-dimensional case. This new approach, which is based on a step-function base profile, is contrasted with the usual time-evolving base state. While both provide only estimates for the instability threshold values, the step-function base profile approach has one great advantage in the sense that the problem at hand can be viewed as a stationary Rayleigh–Bénard problem, the model of which is physically sound and the stability of which is not only well-defined but can be analyzed by a variety of existing analytical methods using only paper and pencil.

Three-dimensional stability analysis for slurry-filled trench wall in cohesionless soil

1996 ◽  
Vol 33 (5) ◽  
pp. 798-808 ◽  
Author(s):  
Jiin-Song Tsai ◽  
Jia-Chyi Chang
Keyword(s):  
Stability Analysis ◽  
Stability Problem ◽  
Slip Surface ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Soil Mass ◽  
Cohesionless Soil ◽  
Cohesionless Soils ◽  
Slurry Trench ◽  
The Stability

On the basis of the limiting equilibrium and arching theory, a three-dimensional analysis is proposed for slurry-supported trenches in cohesionless soils. This analytical approach is developed by considering the trench stability problem as a vertical soil cut within a fictitious half-silo with a rough wall surronding. Arching effects are considered not only in the vertical direction but also in the horizontal direction. A shell-shaped slip surface of the sliding soil mass is defined by Mohr-Coulomb criterion. The factor of safety is defines as the ratio of the resisting force induced by slurry pressure to the horizontal force required to maintain the stability of the trench wall. Results of the proposed method have been compared with those of two existing analytical methods for a typical trench stability problem. Key words: stability analysis, slurry trench wall, cohesionless soil.

scholarly journals Three-dimensional instability of axisymmetric flow in a rotating lid–cylinder enclosure

2001 ◽  
Vol 438 ◽  
pp. 363-377 ◽  
Author(s):  
A. Yu. GELFGAT ◽  
P. Z. BAR-YOSEPH ◽  
A. SOLAN
Keyword(s):  
Stability Problem ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Phase Velocities ◽  
Discrete Values ◽  
The Stability ◽  
Two Parameters ◽  
Dimensional Instability ◽  
Axisymmetric Instability ◽  
Axisymmetric Perturbations

The axisymmetry-breaking three-dimensional instability of the axisymmetric flow between a rotating lid and a stationary cylinder is analysed. The flow is governed by two parameters – the Reynolds number Re and the aspect ratio γ (=height/radius). Published experimental results indicate that in different ranges of γ axisymmetric or non-axisymmetric instabilities can be observed. Previous analyses considered only axisymmetric instability. The present analysis is devoted to the linear stability of the basic axisymmetric flow with respect to the non-axisymmetric perturbations. After the linearization the stability problem separates into a family of quasi-axisymmetric subproblems for discrete values of the azimuthal wavenumber k. The computations are done using the global Galerkin method. The stability analysis is carried out at various densely distributed values of γ in the range 1 < γ < 3.5. It is shown that the axisymmetric perturbations are dominant in the range 1.63 < γ < 2.76. Outside this range, for γ < 1.63 and for γ > 2.76, the instability is three-dimensional and sets in with k = 2 and k = 3 or 4, respectively. The azimuthal periodicity, patterns, characteristic frequencies and phase velocities of the dominant perturbations are discussed.

Stability of columnar convection in a porous medium

2013 ◽  
Vol 737 ◽  
pp. 205-231 ◽  
Author(s):  
Duncan R. Hewitt ◽  
Jerome A. Neufeld ◽  
John R. Lister
Keyword(s):  
Porous Medium ◽  
Linear Stability ◽  
Stability Problem ◽  
Columnar Structure ◽  
Marginal Stability ◽  
Vertically Propagating ◽  
The Stability ◽  
Rayleigh Benard ◽  
Linear Stability Problem ◽  
Dimensional Domain

AbstractConvection in a porous medium at high Rayleigh number $\mathit{Ra}$ exhibits a striking quasisteady columnar structure with a well-defined and $\mathit{Ra}$-dependent horizontal scale. The mechanism that controls this scale is not currently understood. Motivated by this problem, the stability of a density-driven ‘heat-exchanger’ flow in a porous medium is investigated. The dimensionless flow comprises interleaving columns of horizontal wavenumber $k$ and amplitude $\widehat{A}$ that are driven by a steady balance between vertical advection of a background linear density stratification and horizontal diffusion between the columns. Stability is governed by the parameter $A= \widehat{A}\mathit{Ra}/ k$. A Floquet analysis of the linear-stability problem in an unbounded two-dimensional domain shows that the flow is always unstable, and that the marginal-stability curve is independent of $A$. The growth rate of the most unstable mode scales with ${A}^{4/ 9} $ for $A\gg 1$, and the corresponding perturbation takes the form of vertically propagating pulses on the background columns. The physical mechanism behind the instability is investigated by an asymptotic analysis of the linear-stability problem. Direct numerical simulations show that nonlinear evolution of the instability ultimately results in a reduction of the horizontal wavenumber of the background flow. The results of the stability analysis are applied to the columnar flow in a porous Rayleigh–Bénard (Rayleigh–Darcy) cell at high $\mathit{Ra}$, and a balance of the time scales for growth and propagation suggests that the flow is unstable for horizontal wavenumbers $k$ greater than $k\sim {\mathit{Ra}}^{5/ 14} $ as $\mathit{Ra}\rightarrow \infty $. This stability criterion is consistent with hitherto unexplained numerical measurements of $k$ in a Rayleigh–Darcy cell.

On the interaction between Tollmien-Schlichting and Rayleigh-Bénard instabilities in the presence of a longitudinal magnetic field

1983 ◽  
Vol 93 (2) ◽  
pp. 355-377
Author(s):  
N. Rudraiah ◽  
E. S. Shivaraya
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Magnetic Reynolds Number ◽  
Tollmien Schlichting ◽  
Stuart Number ◽  
The Stability ◽  
Rayleigh Benard ◽  
Stable Flow ◽  
Aligned Magnetic Field

AbstractThe method used by Gage and Reid(10) to investigate hydrodynamic stability of thermally stratified fluid is extended to hydromagnetic stability to study the effect of aligned magnetic field on the stability of unstable thermal stratification under the assumption of small magnetic Reynolds number. The interaction between the Tollmien–Schlichting–Stuart mechanism of instability due to shear and magnetic field and Rayleigh–Bénard–Thompson mechanism of instability due to thermally unstable stratification and magnetic field is brought out in detail. It is shown that, although Squire's transformation can be used to reduce the three-dimensional problem to an equivalent two-dimensional one, Squire's theorem is not valid. This conclusion follows from the fact that in our analysis the Richardson number Ri ( < 0) will not be greater than the value −0·92 × 10−6. In particular, it is shown that for the values of stratification parameter n ≤ 0·6 the effect of magnetic field for small values of Stuart number N is to augment instability and impose the restriction on the validity of our numerical procedure. However, for η = 0·8 a sharp transition from unstable to stable flow takes place at N = 0·3. A physical explanation for this based on eddies is given.

scholarly journals Stabilization of a prokaryotic LAT transporter by random mutagenesis

2016 ◽  
Vol 147 (4) ◽  
pp. 353-368 ◽  
Author(s):  
Arturo Rodríguez-Banqueri ◽  
Ekaitz Errasti-Murugarren ◽  
Paola Bartoccioni ◽  
Lukasz Kowalczyk ◽  
Alex Perálvarez-Marín ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Random Mutagenesis ◽  
Membrane Insertion ◽  
Structural Determination ◽  
New Approach ◽  
Membrane Transport Proteins ◽  
Engineer Stability ◽  
The Stability ◽  
Optimal Candidate ◽  
Detergent Micelles

The knowledge of three-dimensional structures at atomic resolution of membrane transport proteins has improved considerably our understanding of their physiological roles and pathological implications. However, most structural biology techniques require an optimal candidate within a protein family for structural determination with (a) reasonable production in heterologous hosts and (b) good stability in detergent micelles. SteT, the Bacillus subtilis l-serine/l-threonine exchanger is the best-known prokaryotic paradigm of the mammalian l–amino acid transporter (LAT) family. Unfortunately, SteT’s lousy stability after extracting from the membrane prevents its structural characterization. Here, we have used an approach based on random mutagenesis to engineer stability in SteT. Using a split GFP complementation assay as reporter of protein expression and membrane insertion, we created a library of 70 SteT mutants each containing random replacements of one or two residues situated in the transmembrane domains. Analysis of expression and monodispersity in detergent of this library permitted the identification of evolved versions of SteT with a significant increase in both expression yield and stability in detergent with respect to wild type. In addition, these experiments revealed a correlation between the yield of expression and the stability in detergent micelles. Finally, and based on protein delipidation and relipidation assays together with transport experiments, possible mechanisms of SteT stabilization are discussed. Besides optimizing a member of the LAT family for structural determination, our work proposes a new approach that can be used to optimize any membrane protein of interest.

Manipulation with a polyarticulated mechanical hand: a new efficient real-time method for computing fingertip forces for a global manipulation strategy

Robotica ◽  
2005 ◽  
Vol 23 (4) ◽  
pp. 479-490 ◽  
Author(s):  
J. P. Gazeau ◽  
S. Zeghloul ◽  
G. Ramirez
Keyword(s):  
Optimization Problem ◽  
Three Dimensional ◽  
Inequality Constraints ◽  
Minimal Distance ◽  
Linear Quadratic ◽  
New Approach ◽  
Three Dimensional Objects ◽  
Mechanical Hand ◽  
The Stability ◽  
Manipulation Strategy

This paper proposes an efficient algorithm for computing finger forces involved in a three-dimensional objects grasp. Effective finger force computation is necessary for the successful manipulation on an object by a multifingered robot hand. Based on previous works, the stability forces are computed as a solution of an optimization problem. This optimization problem is mapped into a linear quadratic problem under inequality constraints. We propose a new approach for this problem: the problem is solved as a minimal distance calculation problem in the forces space. The results obtained by simulation demonstrate the efficiency and the numerical stability of the method. This method is used with the LMS mechanical hand as a component of the global control strategy dedicated to the object manipulation.

scholarly journals Pemikiran Nurcholis Majid dan Pengembangan Pendidikan Islam: Analisis Spirit Keislaman dan Keindonesiaan

2020 ◽  
Vol 3 (2) ◽  
pp. 123
Author(s):  
Siti Mukaromah
Keyword(s):  
Inclusive Education ◽  
Islamic Education ◽  
Religious Fundamentalism ◽  
New Approach ◽  
Library Research ◽  
Alternative Approach ◽  
Qualitative Descriptive ◽  
Truth Claims ◽  
The Stability ◽  
Contemporary Development

The rise of truth claims, radicalism, religious fundamentalism, and the demand of formalization of the khilāfah al Islāmiyah in Indonesia appears to have triggered disharmony in the society and posed threat to the stability of the state. Among the underlying factors contributing to the issue is the approach and method applied in the teaching system of Islamic Education (PAI) which tend to be doctrinal, normative, and exclusive. This has raised awareness of the need to introduce alternative approach in Islamic Education, to accommodate such discourse as multiculturalism, inclusive education based on the spirit of Islam rahmatan lil ‘ālamīn, and respecting the cultural diversity of Indonesian society. Nurcholish Madjid is one of the most prominent Indonesian scholars who actively promote new discourse in Islamic education as he introduces alternative approach and methods based on the spirit of Islam. This research focuses on Nurcholish Madjid’s thoughts on Islamic spirit and indigenous Indonesian identity, especially the extent to which his thoughts have significance in the contemporary development of Islamic Education in Indonesia. This research employs a qualitative-descriptive approach. The data is collected through documentation and reviews of relevant sources. The data analysis shows that Nurcholish Madjid has important thoughts on Islamic education which can be adopted as new approach in the system of Islamic education in Indonesia. Among his thoughts on Islamic education, based on his grand discourse of Islamic spirit and indigenous Indonesian identity, is the need to introduce new discourses of humanism, egalitarian, democratic and inclusive-pluralist within the system of Islamic education in Indonesia.[Maraknya truth claim, radikalisme, politisasi, dan fundamentalisme agama, serta wacana formalisasi syari’at negara khilāfah al Islāmiyah menyebabkan perpecahan dan mengancam stabilitas negara Indonesia. Persoalan tersebut salah satunya dilatarbelakangi oleh pembelajaran Pendidikan Agama Islam (PAI) yang bersifat doktriner, eksklusif dan normatif. Oleh sebab itu, perlu alternatif solusi melalui Pembelajaran Pendidikan Agama Islam yang multikultural, inklusif dan pluralis dengan berbasis pada spirit keislaman dengan membumikan Islam rahmatan lil ‘ālamīn dan spirit keindonesiaan yang menghargai keragaman (pluralitas). Salah satu pemikir dan cendekiawan muslim Indonesia yang aktif menyuarakan spirit keislaman dan keindonesiaan adalah Nurcholish Madjid. Dengan demikian, subjek dalam penelitian ini ialah Nurcholish Madjid mengenai konsep spirit keislaman dan keindonesiaan dan kontribusinya terhadap pengembangan Pendidikan Agama Islam. Pendekatan dalam penelitian ini menggunakan pendekatan kualitatif-deskriptif, dengan jenis penelitian kepustakaan (library research). Pengumpulan data menggunakan metode dokumentasi dengan menganalisis data berupa sumber-sumber dari berbagai literatur yang memiliki persamaan dengan tema penelitian. Hasil penelitian menunjukkan bahwa kontribusi pemikiran Nurcholish Madjid mengenai spirit keislaman dan keindonesiaan terhadap Pengembangan Pendididkan Agama Islam ialah terwujudnya pembelajaran Pendidikan Agama Islam yang humanis, egaliter, demokratis, dan inklusif-pluralis.]

Inviscid spatial stability of a three-dimensional compressible mixing layer

1991 ◽  
Vol 231 ◽  
pp. 35-50 ◽  
Author(s):  
C. E. Grosch ◽  
T. L. Jackson
Keyword(s):  
Dimensional Stability ◽  
Stability Problem ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Mean Flow ◽  
Compressible Mixing Layer ◽  
Spatial Stability ◽  
Family Of Curves ◽  
The Stability

We present the results of a study of the inviscid spatial stability of a parallel three-dimensional compressible mixing layer. The parameters of this study are the Mach number of the fast stream, the ratio of the speed of the slow stream to that of the fast stream, the ratio of the temperature of the slow stream to that of the fast stream, the direction of the crossflow in the fast stream, the frequency, and the direction of propagation of the disturbance wave. Stability characteristics of the flow as a function of these parameters are given. Certain theoretical results are presented which show the interrelations between these parameters and their effects on the stability characteristics. In particular, the three-dimensional stability problem for a three-dimensional mixing layer at Mach zero can be transformed to a two-dimensional stability problem for an equivalent two-dimensional mean flow. There exists a one-parameter family of curves such that for any given direction of mean flow and of wave propagation one can apply this transformation and obtain the growth rate from the universal curves. For supersonic couvective Mach numbers, certain combinations of crossflow angle and propagation angle of the disturbance can increase the growth rates by a factor of about two. and thus enhance mixing.

scholarly journals Stability boundaries of roll and square convection in binary fluid mixtures with positive separation ratio

2000 ◽  
Vol 408 ◽  
pp. 121-147 ◽  
Author(s):  
B. HUKE ◽  
M. LÜCKE ◽  
P. BÜCHEL ◽  
CH. JUNG
Keyword(s):  
Three Dimensional ◽  
Stationary Solutions ◽  
Stability Boundaries ◽  
Binary Fluid ◽  
Fluid Mixtures ◽  
Separation Ratio ◽  
Wide Range ◽  
The Stability ◽  
Binary Fluid Mixtures ◽  
Rayleigh Benard

Rayleigh–Bénard convection in horizontal layers of binary fluid mixtures heated from below with realistic horizontal boundary conditions is studied theoretically using multi-mode Galerkin expansions. For positive separation ratios the main difference between the mixtures and pure fluids lies in the existence of stable three-dimensional patterns near onset in a wide range of the parameter space. We evaluated the stationary solutions of roll, crossroll, and square convection and we determined the location of the stability boundaries for many parameter combinations thereby obtaining the Busse balloon for roll and square patterns.

A Liquid Metal Flow Between Two Coaxial Cylinders System

2019 ◽  
Vol 11 (1) ◽  
pp. 79-86
Author(s):  
Abdelkrim Merah ◽  
Ridha Kelaiaia ◽  
Faiza Mokhtari
Keyword(s):  
Couette Flow ◽  
Metal Flow ◽  
Three Dimensional ◽  
Liquid Sodium ◽  
Taylor Vortex ◽  
Turbulent Regime ◽  
Coaxial Cylinders ◽  
Concentric Cylinders ◽  
Ideal Tool ◽  
The Stability

Abstract The Taylor-Couette flow between two rotating coaxial cylinders remains an ideal tool for understanding the mechanism of the transition from laminar to turbulent regime in rotating flow for the scientific community. We present for different Taylor numbers a set of three-dimensional numerical investigations of the stability and transition from Couette flow to Taylor vortex regime of a viscous incompressible fluid (liquid sodium) between two concentric cylinders with the inner one rotating and the outer one at rest. We seek the onset of the first instability and we compare the obtained results for different velocity rates. We calculate the corresponding Taylor number in order to show its effect on flow patterns and pressure field.

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