Theoretical Prediction of Onset of Horizontal Slug Flow

1980 ◽  
Vol 102 (4) ◽  
pp. 441-445 ◽  
Author(s):  
Kaichiro Mishima ◽  
Mamoru Ishii
Keyword(s):  
Experimental Data ◽  
Stability Analysis ◽  
Slug Flow ◽  
Flow Analysis ◽  
Finite Amplitude ◽  
Empirical Correlations ◽  
Deformation Limit ◽  
Theoretical Criterion ◽  
The Stability ◽  
Good Agreement

A criterion for the onset of a slug flow in a horizontal duct is derived theoretically. A potential flow analysis is carried out by considering waves of finite amplitude. The stability criterion is obtained by introducing the wave deformation limit and the “most dangerous wave” concept in the stability analysis. The present theoretical criterion for slug formation shows very good agreement with a large number of experimental data and with some empirical correlations.

Global Stability Analysis of the Wake behind a Circular Cylinder Based on the POD-Chiba Method

2011 ◽  
Vol 137 ◽  
pp. 72-76
Author(s):  
Wei Zhang ◽  
Xian Wen ◽  
Yan Qun Jiang
Keyword(s):  
Stability Analysis ◽  
Circular Cylinder ◽  
Global Stability ◽  
Dimensional Model ◽  
Global Stability Analysis ◽  
The Stability ◽  
Low Dimensional ◽  
Proper Orthogonal ◽  
Calculated Amount ◽  
Good Agreement

A proper orthogonal decomposition (POD) method is applied to study the global stability analysis for flow past a stationary circular cylinder. The flow database at Re=100 is obtained by CFD software, i.e. FLUENT, with which POD bases are constructed by a snapshot method. Based on the POD bases, a low-dimensional model is established for solving the two-dimensional incompressible NS equations. The stability of the flow solution is evaluated by a POD-Chiba method in the way of the eigensystem analysis for the velocity disturbance. The linear stability analysis shows that the first Hopf bifurcation takes place at Re=46.9, which is in good agreement with available results by other high-order accurate stability analysis methods. However, the calculated amount of POD is little, which shows the availability and advantage of the POD method.

On the Development of Transverse Ridges on Rock Glaciers

1989 ◽  
Vol 35 (121) ◽  
pp. 383-391 ◽  
Author(s):  
Deborah S. Loewenherz ◽  
Christopher J. Lawrence ◽  
Richard L. Weaver
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
Lower Layer ◽  
Elastic Solid ◽  
Surface Region ◽  
Finite Amplitude ◽  
Climatic Conditions ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
The Stability

AbstractThe stability of a low Reynolds number flow on an inclined plane is investigated with respect to modelling the initiation of transverse wave-like ridges which commonly occur on the surfaces of rock-glacier forms. In accordance with field observations indicating the presence of stratification in rock glaciers, two models of rock-glacier structure are considered, each stratified and possessing a lower layer which is treated as a Newtonian fluid. An upper, less compliant layer is treated, alternatively, as a Newtonian fluid of viscosity greater than that of the lower layer, or as an elastic solid under longitudinal compression induced by a decrease in the slope of the underlying incline. A linear stability analysis is used to examine the behaviour of each of the proposed models, and both are found to generate instabilities at wavelengths comparable to those associated with transverse surficial ridges on rock glaciers. The growth rates of a flow disturbance predicted by the viscous-stratified model appear to be too slow to account fully for the development of wave forms of finite amplitude, suggesting that other mechanisms are involved in the amplification of an initial disturbance. The results of the stability analysis of the elastic lamina model indicate that finite surficial ridges may develop on rock glaciers as a product of a buckling instability in the surface region if there is a decrease in the slope of the underlying incline. Both of the analyses illustrate that transverse ridges can occur on the surface of a rock glacier in the absence of any variations in debris supply to the system. The results further imply that the use of these features in the paleoreconstruction of Holocene climatic conditions must entail an assessment of the relative roles of external climatically driven forcingversusinternal Theologically derived instability.

scholarly journals Stability Analysis of Dike to Impound Freshwater in Brackish Water Estuarine Environment

2020 ◽  
Vol 14 (1) ◽  
pp. 139-149
Author(s):  
Amala Krishnan ◽  
Sreevalsa Kolathayar
Keyword(s):  
Stability Analysis ◽  
Brackish Water ◽  
High Tide ◽  
Estuarine Environment ◽  
Water Demands ◽  
River Flood ◽  
The Stability ◽  
River Dike ◽  
Underlying Soil ◽  
Good Agreement

This paper presents the stability analysis of a dike proposed to impound the river flood waters within an estuary near the west coast of south India. The proposed dike will be located within Ashtamudi Lake, the second largest lake in the state of Kerala, India, separating fresh water from brackish water. Constructing a dike at Munro Island portion of Ashtamudi, which is about 9.23 km from Arabian Sea coast, can meet the water demands of the region as well as prevent the sinking of Island during high tide. The river dike is designed to construct artificially as rock filled structures. The stratigraphy in the top 2 m consists of clayey mud underlined by fine to medium sand up to 6 m followed by alternate layers of clay and sand up the investigated depth of 15 m. In this paper, the stability of the dike located in an estuarine environment has been investigated and the factor of safety values have been determined with varying water level conditions and varying properties of the underlying soil. A detailed parametric study using RocScience software is presented, considering all the design conditions. The expected settlement of the dike is estimated considering the soil profile at the location both manually as well as using software Geo5. Both were in good agreement and the maximum possible settlement was found to be less than half a meter.

scholarly journals Stability analysis of cylindrical shells subjected to complex loads

2001 ◽  
Vol 23 (4) ◽  
pp. 247-256
Author(s):  
Ngo Huong Nhu
Keyword(s):  
Cylindrical Shell ◽  
Stability Analysis ◽  
Composite Shell ◽  
Laminated Composite ◽  
Numerical Results ◽  
Load Pressure ◽  
Combined Loads ◽  
Analytical Result ◽  
The Stability ◽  
Good Agreement

The paper deals with stability analysis of shell on the basis FEM via Castem 2000. The numerical results of stability problems of cylinders subjected to different loads as compress load, pressure, concentrated and combined loads are compared with analytical result and give a good agreement. The influence of changing radius of the cylindrical shell on the unstable forms and the influence of angles of fibers on unstable behaviour of laminated composite shell are considered. Numerical results and corresponding programs by languages Gibian given in the paper to realize software Castem 2000 can be applied in the design and in the stability analysis of the shell with more complex conditions

Stability of Ring-Stiffened Tubular Members Under External Pressure

1995 ◽  
Vol 117 (2) ◽  
pp. 150-155 ◽  
Author(s):  
S. A. Karamanos ◽  
J. L. Tassoulas
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Stability Analysis ◽  
External Pressure ◽  
Nonlinear Finite Element ◽  
Steel Tubes ◽  
Deformation Plasticity ◽  
The Stability ◽  
Element Technique ◽  
Stiffened Steel

This paper presents results of a rigorous nonlinear finite element technique for the stability analysis of ring-stiffened steel tubes under external pressure. Large deformation, plasticity, as well as residual stresses and imperfections, are taken into account. Both internal and external stiffeners are simulated. A study of various parameters which affect pressure capacity is summarized, along with a comparison with available experimental data.

On the Development of Transverse Ridges on Rock Glaciers

1989 ◽  
Vol 35 (121) ◽  
pp. 383-391
Author(s):  
Deborah S. Loewenherz ◽  
Christopher J. Lawrence ◽  
Richard L. Weaver
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
Lower Layer ◽  
Elastic Solid ◽  
Surface Region ◽  
Finite Amplitude ◽  
Climatic Conditions ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
The Stability

AbstractThe stability of a low Reynolds number flow on an inclined plane is investigated with respect to modelling the initiation of transverse wave-like ridges which commonly occur on the surfaces of rock-glacier forms. In accordance with field observations indicating the presence of stratification in rock glaciers, two models of rock-glacier structure are considered, each stratified and possessing a lower layer which is treated as a Newtonian fluid. An upper, less compliant layer is treated, alternatively, as a Newtonian fluid of viscosity greater than that of the lower layer, or as an elastic solid under longitudinal compression induced by a decrease in the slope of the underlying incline. A linear stability analysis is used to examine the behaviour of each of the proposed models, and both are found to generate instabilities at wavelengths comparable to those associated with transverse surficial ridges on rock glaciers. The growth rates of a flow disturbance predicted by the viscous-stratified model appear to be too slow to account fully for the development of wave forms of finite amplitude, suggesting that other mechanisms are involved in the amplification of an initial disturbance. The results of the stability analysis of the elastic lamina model indicate that finite surficial ridges may develop on rock glaciers as a product of a buckling instability in the surface region if there is a decrease in the slope of the underlying incline. Both of the analyses illustrate that transverse ridges can occur on the surface of a rock glacier in the absence of any variations in debris supply to the system. The results further imply that the use of these features in the paleoreconstruction of Holocene climatic conditions must entail an assessment of the relative roles of external climatically driven forcing versus internal Theologically derived instability.

scholarly journals Modelling of Transient Slug Flow in Pipeline

1997 ◽  
Author(s):  
T. N. Wong ◽  
Y. K. Yau
Keyword(s):  
Experimental Data ◽  
Theoretical Prediction ◽  
Slug Flow ◽  
Valve Closure ◽  
Liquid Slug ◽  
Proposed Model ◽  
Pressure Surge ◽  
Slug Flows ◽  
Gas Expansion ◽  
Good Agreement

An approach to model slug flow in horizontal pipeline is presented which is based on a transient Lagrangian formulation. The effect of slug growth is modelled by considering the gas expansion, picking up of liquid film ahead of the slug and shading of liquid from the slug tail. This method is particular useful for slug flows approaching the end of a pipeline. The validation of the theoretical prediction is confirmed by comparing with the experimental measurement. The proposed model is further used to analyse shock phenomenon caused by a rapid valve closure in a gas-liquid slug flows system. The results show that the pressure surge is highly dependent on the local void fraction at the valve during closure. Good agreement has been obtained between prediction and experimental data by Akagawa et al (1982).

The instability of the thin vortex ring of constant vorticity

1977 ◽  
Vol 287 (1344) ◽  
pp. 273-305 ◽  
Keyword(s):  
Stability Analysis ◽  
Vortex Ring ◽  
Mean Flow ◽  
Bending Waves ◽  
Constant Vorticity ◽  
Ring Radius ◽  
Amplification Rate ◽  
The Mean ◽  
The Stability ◽  
Good Agreement

A theoretical investigation of the instability of a vortex ring to short azimuthal bending waves is presented. The theory considers only the stability of a thin vortex ring with a core of constant vorticity (constant /r) in an ideal fluid. Both the mean flow and the disturbance flow are found as an asymptotic solution in e = a /R, the ratio of core radius to ring radius. Only terms linear in wave amplitude are retained in the stability analysis. The solution to 0 (e 2 ) is presented, although the details of the stability analysis are carried through completely only for a special class of bending waves that are known to be unstable on a line filament in the presence of strain (Tsai & Widnall 1976) and have been identified in the simple model of Widnall, Bliss & Tsai (1974) as a likely mode of instability for the vortex ring: these occur at certain critical wavenumbers for which waves on a line filament of the same vorticity distribution would not rotate (w 0 = 0). The ring is found to be always unstable for at least the lowest two critical wavenumbers ( ka = 2.5 and 4.35). The amplification rate and wavenumber predicted by the theory are found to be in good agreement with available experimental results.

Linear and Nonlinear PSE for Stability Analysis of the Blasius Boundary Layer Using Compact Scheme

2001 ◽  
Vol 123 (3) ◽  
pp. 545-550 ◽  
Author(s):  
V. Esfahanian ◽  
K. Hejranfar ◽  
F. Sabetghadam
Keyword(s):  
Stability Analysis ◽  
Three Dimensional ◽  
Nonlinear Effects ◽  
Numerical Investigations ◽  
Blasius Boundary Layer ◽  
Incompressible Boundary ◽  
Linear And Nonlinear ◽  
Tollmien Schlichting ◽  
The Stability ◽  
Good Agreement

A highly accurate finite-difference PSE code has been developed to investigate the stability analysis of incompressible boundary layers over a flat plate. The PSE equations are derived in terms of primitive variables and are solved numerically by using compact method. In these formulations, both nonparallel as well as nonlinear effects are accounted for. The validity of present numerical scheme is demonstrated using spatial simulations of two cases; two-dimensional (linear and nonlinear) Tollmien-Schlichting wave propagation and three-dimensional subharmonic instability breakdown. The PSE solutions have been compared with previous numerical investigations and experimental results and show good agreement.

Stability analysis of two coupled pre-shaped beams in parallel

2017 ◽  
Vol 232 (13) ◽  
pp. 2482-2489 ◽  
Author(s):  
Wu Zhou ◽  
Huiju Yu ◽  
Lili Chen ◽  
Yu Chen ◽  
Bei Peng ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Analytical Methods ◽  
Nonlinear Phenomenon ◽  
Single Beam ◽  
Fabrication Errors ◽  
Coupled Beams ◽  
The Stability ◽  
Bistable Mechanism ◽  
Minimum Force ◽  
Good Agreement

Parallel bistable mechanism rather than single bistable beam is preferred in micro devices like relays and resonators due to its higher stability in insensitive axis and higher robustness to fabrication errors. Its stability characteristics including nonlinearity and bistability or snap-through, however, rarely appear in current publications. The coupled mechanism constructed by two pre-shaped beams in parallel is investigated analytically and numerically in this paper. Based on the quasi-linearization of the problem and analytical equation of force and displacement, the dimension combinations of coupled beams are categorized into three types according to the apex amplitudes of cosine-shaped beams. It is concluded that the appearance of snap-through behaviors in parallel coupled mechanism is sustained by both arranging two bistable beams and making the apex difference meet condition of Fmin < 0. The smallest values of minimum force only appears when the apexes are equal to each other, and any efforts to increase or decrease the apex of single beam will lead the nonlinear phenomenon from snap-through to constrained-snap-through and further to no snap-through. The numerical method is also introduced to observe the stability of coupled mechanism and shows a good agreement with analytical methods proposed by this paper.

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