scholarly journals Effect of Interface Momentum Distribution on the Stability in a Porous-Fluid System

2020 ◽  
Vol 13 (3) ◽  
pp. 1037-1046
Author(s):  
P. Hu ◽  
Q. Li ◽  
◽  
Keyword(s):  
Momentum Distribution ◽  
Fluid System ◽  
The Stability

Dynamic Stability of Isotropic or Composite-Material Cylindrical Shells Containing Swirling Fluid Flow

1977 ◽  
Vol 44 (1) ◽  
pp. 112-116 ◽  
Author(s):  
T. L. C. Chen ◽  
C. W. Bert
Keyword(s):  
Shell Theory ◽  
Swirling Flow ◽  
Circular Cylindrical Shell ◽  
Critical Flow ◽  
Fluid System ◽  
Critical Flow Velocity ◽  
Rotating Speed ◽  
Fluid Forces ◽  
Shell Motion ◽  
The Stability

A linear stability analysis is presented for a thin-walled, circular cylindrical shell of orthotropic material conveying a swirling flow. Shell motion is modeled by using the dynamic orthotropic version of the Sanders shell theory and fluid forces are described by inviscid, incompressible flow theory. The critical flow velocities are determined for piping made of composite and isotropic materials conveying swirling water. Fluid rotation strongly degrades the stability of the shell/fluid system, i.e. increasing the fluid rotating speed severely decreases the critical flow velocity.

A New Method for Predicting the Critical Taylor Number in Rotating Cylindrical Flows

1987 ◽  
Vol 54 (3) ◽  
pp. 713-719 ◽  
Author(s):  
J. O. Cruickshank
Keyword(s):  
Dynamic Stability ◽  
Critical Stress ◽  
Stress Condition ◽  
Flow Instability ◽  
Fluid System ◽  
Fluid Systems ◽  
Concentric Cylinders ◽  
Elastic Systems ◽  
Subsequent Motion ◽  
The Stability

A method for determining the boundaries of dynamic stability of a fluid system, as distinct from the prediction of the subsequent motion, is presented. The method is based on well-known approaches to the problem of instability in elastic systems. The extension of these methods to fluid systems, specifically, to the stability of flow between concentric cylinders, confirms that it may be possible in some cases to determine the boundaries of stability of fluid systems without recourse to an Orr-Sommerfeld type treatment. The results also suggest that the concept of apparent (virtual) viscosity may have implications for fluid stability outside the current realm of turbulence modelling. Finally, it is also shown that flow instability may be preceded by the onset of a critical stress condition in analogy with elastic systems.

Two-fluid gravitational instabilities in a galactic disk

1985 ◽  
Vol 106 ◽  
pp. 505-508
Author(s):  
Chanda J. Jog
Keyword(s):  
Galactic Disk ◽  
Random Motion ◽  
Hydrodynamic Equations ◽  
Fluid System ◽  
Gravitational Instabilities ◽  
Velocity Dispersions ◽  
The Stability ◽  
The One ◽  
Two Fluid ◽  
Perturbation Equations

We formulate and solve the hydrodynamic equations describing an azimuthally symmetric galactic disk as a two-fluid system. The stars and the gas are treated as two different isothermal fluids of different velocity dispersions (CS ≫ Cg), which interact gravitationally with each other. The disk is supported by rotation and random motion. The formulation of the equations closely follows the one-fluid treatment by Toomre (1964). We solve the linearized perturbation equations by the method of modes, and study the stability of the galactic disk against the growth of axisymmetric two-fluid gravitational instabilities.

scholarly journals Determination of Natural Frequency and Critical Velocity of Inclined Pipe Conveying Fluid under Thermal Effect by Using Integral Transform Technique

2021 ◽  
Vol 7 (1) ◽  
pp. 41-55
Author(s):  
Jabbar Hussein Mohmmed ◽  
Mauwafak Ali Tawfik ◽  
Qasim Abbas Atiyah
Keyword(s):  
Analytical Solution ◽  
Temperature Variation ◽  
Integral Transform ◽  
Fluid Velocity ◽  
Harmful Effect ◽  
Fluid System ◽  
Flowing Fluid ◽  
Time Domain Response ◽  
The Stability ◽  
Integral Transform Technique

This study proposes an analytical solution of natural frequencies for an inclined fixed supported Euler-Bernoulli pipe containing the flowing fluid subjected to thermal loads. The integral transform technique is employed to obtain the spatial displacement-time domain response of the pipe-fluid system. Then, a closed-form analytical expression is presented. The effects of various geometric and system parameters on the vibration characteristics of pipe-fluid system with different flow velocities are discussed. The results illustrate that the proposed analytical solution agrees with the solutions achieved in previous works. The proposed model predicts that the pipe loses the stability by divergence with the increasing flow velocity. It is evident that the influences of inclination angle and temperature variation are dramatically increased at a higher aspect ratio. Additionally, it is demonstrated that the temperature variation becomes a more harmful effect than the internal fluid velocity on the stability of the pipe at elevated temperature.

A Physical Explanation of the Destabilizing Effect of Damping

1998 ◽  
Vol 65 (3) ◽  
pp. 642-648 ◽  
Author(s):  
C. Semler ◽  
H. Alighanbari ◽  
M. P. Pai¨doussis
Keyword(s):  
Mathematical Explanation ◽  
Pipe Conveying Fluid ◽  
Key Factors ◽  
Physical Explanation ◽  
Fluid System ◽  
Force System ◽  
Modes Of Vibration ◽  
The Stability ◽  
Phase Angles ◽  
Conveying Fluid

In this paper, the destabilization due to small damping of the follower force system, known as Beck’s problem, and of the cantilevered pipe conveying fluid system, two nonconservative systems, is considered. Instead of looking for a mathematical explanation, e.g., the evolution of the eigenvalues with different parameters, a more “physical” explanation is provided. It is shown that it is of particular interest to focus on the different modes of vibration and to understand how they evolve when damping is varied. Also, based on energy considerations, the key factors influencing stability are highlighted, e.g., the phase angles between the different coordinates. In the case of the pipe conveying fluid, the methodology developed and insight gained help explain the presence of “jumps” p in the stability curves, that are known to play an important role in the linear and nonlinear dynamics of this system.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

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