scholarly journals Discussion: “On the Dynamics of Stability of Cylindrical Shells Conveying Inviscid or Viscous Fluid in Internal or Annular Flow” (El Chebair, A., and Misra, A. K., 1991, ASME J. Pressure Vessel Technol., 113, pp. 409–417)

1992 ◽  
Vol 114 (1) ◽  
pp. 132-132
Author(s):  
C. Dupuis ◽  
J. Rousselet
Keyword(s):  
Viscous Fluid ◽  
Pressure Vessel ◽  
Annular Flow ◽  
Cylindrical Shells

Dynamics and Stability of Coaxial Cylindrical Shells Conveying Viscous Fluid

1985 ◽  
Vol 52 (2) ◽  
pp. 389-396 ◽  
Author(s):  
M. P. Paidoussis ◽  
A. K. Misra ◽  
S. P. Chan
Keyword(s):  
Viscous Fluid ◽  
Annular Flow ◽  
Cylindrical Shells ◽  
Inviscid Flow ◽  
Viscous Effects ◽  
Fluid Forces ◽  
Frictional Pressure Drop ◽  
Generalized Force ◽  
Shell Equations ◽  
Shell Vibration

In this paper the dynamics and stability characteristics of coaxial cylindrical shells containing incompressible, viscous fluid flow are examined in contrast to previous studies where the fluid has been considered to be inviscid. Specifically, upstream pressurization of the flow (to overcome frictional pressure drop) and skin friction on the shell surfaces are taken into account, generating time-mean normal and tangential loading on the shells. Shell motions are described by Flu¨gge’s thin shell equations, suitably modified to incorporate the time-mean stress resultants arising from viscous effects. The fluctuating fluid forces, coupled to shell vibration, are determined entirely by means of linearized potential flow theory and formulated with the aid of generalized-force Fourier-transform techniques. It is found that the effect of viscosity in the annular flow generally tends to destabilize the system, vis-a`-vis inviscid flow, whereas viscous effects in the inner flow stabilize the system. These effects can be quantitatively very important, so that, generally, neglect of viscous effects cannot be justified.

Tensile Plastic Instability of Axisymmetric Pressure Vessels

1998 ◽  
Vol 120 (1) ◽  
pp. 6-11 ◽  
Author(s):  
D. P. Updike ◽  
A. Kalnins
Keyword(s):  
Pressure Vessel ◽  
Detrimental Effect ◽  
Cylindrical Shells ◽  
Plastic Instability ◽  
Pressure Vessels ◽  
Reduction Factor ◽  
Test Results ◽  
Strength Reduction Factor ◽  
Burst Data ◽  
Longitudinal Welds

This paper examines the calculated pressure at a tensile plastic instability of a pressure vessel and its relationship to burst test results. It is proposed that the instability pressure be accepted as an upper bound to the pressure at which a vessel bursts, and that a strength reduction factor be used to predict the burst. The paper also presents a suitable mathematical model for the calculation of the instability pressures for thin-walled axisymmetric vessels. The proposition is tested by applying the model to a pressurized diaphragm, four cylindrical shells, and two torispherical heads, for which experimental burst data are available. It is found that the ratio of the test burst pressure to the calculated pressure at the tensile plastic instability, expressed in percent, ranges from 71 to 96 percent. The highest ratio occurs for a pressurized diaphragm with no significant defects. The lowest ratios occur for cylindrical shells with longitudinal welds, suggesting that the presence of the welds had a detrimental effect on the burst strength. These results may be useful when designing a pressure vessel with respect to its ultimate strength.

scholarly journals Exchange flow of two immiscible fluids and the principle of maximum flux

2011 ◽  
Vol 682 ◽  
pp. 132-159 ◽  
Author(s):  
R. R. KERSWELL
Keyword(s):  
Viscous Fluid ◽  
Annular Flow ◽  
Viscosity Ratio ◽  
Cylindrical Tube ◽  
Immiscible Fluids ◽  
Exchange Flow ◽  
Two Phase ◽  
Full Circle ◽  
Flow Situation ◽  
Principle Of Maximum

The steady, coaxial flow in which two immiscible, incompressible fluids of differing densities move past each other slowly in a vertical cylindrical tube has a continuum of possibilities due to the arbitrariness of the interface between the fluids. By invoking the presence of surface tension to at least restrict the shape of any interface to that of a circular arc or full circle, we consider the following question: which flow will maximise the exchange when there is only one dividing interface Γ? Surprisingly, the answer differs fundamentally from the better-known co-directional two-phase flow situation where an axisymmetric (concentric) core-annular solution always optimises the flux. Instead, the maximal flux state is invariably asymmetric either being a ‘side-by-side’ configuration where Γ starts and finishes at the tube wall or an eccentric core-annular flow where Γ is an off-centre full circle in which the more viscous fluid is surrounded by the less viscous fluid. The side-by-side solution is the most efficient exchanger for a small viscosity ratio β ≲ 4.60 with an eccentric core-annular solution optimal otherwise. At large β, this eccentric solution provides 51% more flux than the axisymmetric core-annular flow which is always a local minimiser of the flux.

Convective/absolute instability in miscible core-annular flow. Part 2. Numerical simulations and nonlinear global modes

2009 ◽  
Vol 618 ◽  
pp. 323-348 ◽  
Author(s):  
B. SELVAM ◽  
L. TALON ◽  
L. LESSHAFFT ◽  
E. MEIBURG
Keyword(s):  
Viscous Fluid ◽  
Numerical Simulations ◽  
Annular Flow ◽  
Nonlinear Oscillations ◽  
Variable Viscosity ◽  
Base Flow ◽  
Absolute Instability ◽  
Infinite Domain ◽  
Global Mode ◽  
The Core

The convective/absolute nature of the instability of miscible core-annular flow with variable viscosity is investigated via linear stability analysis and nonlinear simulations. From linear analysis, it is found that miscible core-annular flows with the more viscous fluid in the core are at most convectively unstable. On the other hand, flows with the less viscous fluid in the core exhibit absolute instability at high viscosity ratios, over a limited range of core radii. Nonlinear direct numerical simulations in a semi-infinite domain display self-excited intrinsic oscillations if and only if the underlying base flow exhibits absolute instability. This oscillator-type flow behaviour is demonstrated to be associated with the presence of a nonlinear global mode. Both the parameter range of global instability and the intrinsically selected frequency of nonlinear oscillations, as observed in the simulation, are accurately predicted from linear criteria. In convectively unstable situations, the flow is shown to respond to external forcing over an unstable range of frequencies, in quantitative agreement with linear theory. As discussed in part 1 of this study (d'Olce, Martin, Rakotomalala, Salin and Talon,J. Fluid Mech., vol. 618, 2008, pp. 305–322), self-excited synchronized oscillations were also observed experimentally. An interpretation of these experiments is attempted on the basis of the numerical results presented here.

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