scholarly journals Dynamic Behavior of Tubes Subjected to Internal and External Cross Flows

1997 ◽  
Vol 4 (2) ◽  
pp. 77-91 ◽  
Author(s):  
Yii-Mei Huang ◽  
Chih-Shan Hsu
Keyword(s):  
Dynamic Characteristics ◽  
Multiple Scales ◽  
Cross Flow ◽  
Internal Flow ◽  
Numerical Approach ◽  
Small Time ◽  
Steady Flows ◽  
Thin Cylindrical Shell ◽  
Pressure Distributions ◽  
The Stability

This article presents a method for thoroughly examining the dynamic characteristics of a tube under the influence of either the internal flow or the external cross flow. The tube is modeled as a thin cylindrical shell whose governing equations are derived from an energy method. The effects due to internal flow are introduced into the system through initial stress. Galerkin’s method in conjunction with the method of multiple scales is employed for obtaining the stability of the tube vibration. According to the results, instability can occur under certain conditions of resonance. Regarding the effects of the external cross flow, a numerical approach is initially employed to interpolate the experimental data of the pressure distributions due to the flow. The dynamic characteristics of the tube under steady flows and flows with small time variation are then investigated. Stability of the solution is also discussed.

ANALYSIS OF NONLINEAR MAGNETOELASTIC DYNAMICS AND STABILITY OF CONDUCTIVE CYLINDRICAL SHELLS

2010 ◽  
Vol 10 (01) ◽  
pp. 153-164
Author(s):  
YUDA HU ◽  
JIANG ZHAO ◽  
PI JUN ◽  
GUANGHUI QING
Keyword(s):  
Cylindrical Shell ◽  
Multiple Scales ◽  
Method Of Multiple Scales ◽  
Approximate Analytical Solution ◽  
Transverse Magnetic ◽  
Field Equations ◽  
Thin Cylindrical Shell ◽  
The Stability ◽  
Magnetic Induction Intensity ◽  
Steady State Solutions

The nonlinear magnetoelastic vibration equations and electromagnetic field equations of a conductive thin cylindrical shell in magnetic fields are derived. The nonlinear principal resonances and dynamic stabilities of the cylindrical shell simply supported in a transverse magnetic field are investigated. Approximate analytical solution and bifurcation equations of the system with principal resonances are obtained by using the method of multiple scales. The stabilities and singularities of the steady-state solutions are analyzed and the stability criterion is given. The transition sets and bifurcation figures of unfolding parameters are also obtained. The variations of the resonance amplitudes with respect to the detuning parameter, the magnetic induction intensity, and the amplitude of excitations are presented. The corresponding phase trajectories in moving phase planes are given. The stabilities of solutions, characteristics of singular points, and bifurcation are analyzed. The impacts of electromagnetic and mechanical parameters on dynamic behaviors are discussed in detail.

Flow-induced Instabilities of Cylindrical Structures

1987 ◽  
Vol 40 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Michael P. Paidoussis
Keyword(s):  
Annular Flow ◽  
Dynamical Behavior ◽  
Cross Flow ◽  
Axial Flow ◽  
Internal Flow ◽  
Internal Flows ◽  
Cylindrical Structures ◽  
Curved Pipes ◽  
The Stability ◽  
The Many

A kaleidoscopic view of the many diverse and interesting instabilities are presented, to which cylindrical structures are susceptible when in contact with flowing fluids. The physical mechanisms involved are discussed in each case, to the extent that they are understood, and the degree of success of available mathematical models is assessed. Four classes of problems are dealt with, according to the disposition of the flow vis-a`-vis the cylindrical structures: (a) instabilities induced by internal flows in tubular structures; (b) instabilities of solitary or clustered cylinders due to external axial flow; (c) annular-flow-induced instabilities of coaxial beams and shells; (d) instabilities of arrays of cylinders subject to cross-flow. In the first class of problems, the stability of straight tubular beams and cylindrical shells conveying fluid is discussed first, followed by the stability of curved pipes containing flow. In the second class of problems, the instabilities of solitary and clustered cylinders subjected to an external axial flow are treated, and their dynamical behavior is compared to that of systems with internal flow. The third class of problems involves annular flow in coaxial systems of beams and/or shells. Cross-flow-induced instabilities of clustered cylinders, in the form of arrays of different geometrical patterns, are the last class of problems considered; they are fundamentally distinct from the foregoing in terms of the fluid mechanics of the problem, for in this case the flow field is not irrotational—not even approximately.

scholarly journals Dynamic Characteristics and Stability of Flexible Riser Under Consideration of Non-Uniform Tension and Internal Flow

2020 ◽  
Author(s):  
Dingbang Yan ◽  
Shuangxi Guo ◽  
Yilun Li ◽  
Jixiang Song ◽  
Min Li ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Oil And Gas ◽  
Internal Flow ◽  
Oil And Gas Industry ◽  
Travelling Wave ◽  
Flexible Riser ◽  
Modal Shape ◽  
Gas Industry ◽  
Uniform Tension ◽  
The Stability

Abstract As oil and gas industry is developing towards deeper ocean area, the length and flexibility of ocean risers become larger, which may induce larger-amplitude displacement of flexible riser response due to lower structural stiffness against environmental and operational loads. Moreover, suffering not only the external fluid loads coming from environmental ocean wave and current, these risers also convey internal flow. In other words, the dynamic characteristics and response of the flow-conveying riser face great challenge, such as bucking, divergence and flutter, because of the fluid-solid coupling of the internal hydrodynamics and riser structural dynamics. In this study the dynamic characteristics and stability of a flexible riser, under consideration of its internal flow and, particularly, non-uniform axial tension, are examined through our FEM numerical simulations. First, the governing equations and FEM models of a flexible riser with axially-varying tension and internal flow are developed. Then the dynamic characteristics, including the coupled frequency and modal shape, are presented, as considering the speed of internal speed changes. At last, the dynamic response and corresponding stability behaviors are discussed and compared with the cases of riser with uniform tension. Our FEM results show that the stability and response are quite different from riser with uniform tension. And, the time-spatial evolution of riser displacement exhibit a strong wave propagation phenomenon where travelling wave are observed.

Nonlinear Vibration and Stability Analysis of Embedded Carbon Nanotubes With Internal Flow

2010 ◽  
Author(s):  
M. Rasekh ◽  
S. E. Khadem
Keyword(s):  
Carbon Nanotube ◽  
Nonlinear Vibration ◽  
Elastic Medium ◽  
Multiple Scales ◽  
Internal Flow ◽  
Beam Theory ◽  
Response Curves ◽  
Critical Flow Velocity ◽  
Aspect Ratios ◽  
The Stability

In this paper, for the first time, the influence of internal moving fluid on the nonlinear vibration and stability of embedded carbon nanotube is investigated. The Euler-Bernoulli beam theory is employed to model the vibrational behavior of an embedded carbon nanotube. The relationship of nonlinear amplitude and frequency for the single-wall nanotubes in the presence of internal fluid flow is expressed using the multiple scales perturbation method. The amplitude-frequency response curves of the nonlinear vibration obtained and the effects of the surrounding elastic medium, mass and the aspect ratios of nanotubes are discussed. It is shown that beyond the critical flow velocity buckling occurs and surrounding elastic medium plays a significant role in the stability of the carbon nanotube.

Instabilities of flow in a collapsed tube

1990 ◽  
Vol 220 ◽  
pp. 623-659 ◽  
Author(s):  
O. E. Jensen
Keyword(s):  
Dynamical Behaviour ◽  
Small Time ◽  
Neutral Stability ◽  
Steady Flows ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Analysis ◽  
Neutral Curves ◽  
Through Flow ◽  
Longitudinal Wall ◽  
The Stability

In a previous paper (Jensen & Pedley 1989) a model was analysed describing the effects of longitudinal wall tension and energy loss through flow separation on the existence and nature of steady flow in a finite length of externally pressurized, elastic-walled tube. The stability of these steady flows to small time-dependent perturbations is now determined. A linear analysis shows that the tube may be unstable to at least three different modes of oscillation, with frequencies in distinct bands, depending on the governing parameters; neutral stability curves for each mode are calculated. The motion of the separation point at a constriction in the tube appears to play an important role in the mechanism of these oscillations. A weakly nonlinear analysis is used to examine the instabilities in a neighbourhood of their neutral curves and to investigate mode interactions. The existence of multiple independent oscillations indicates that very complex dynamical behaviour may occur.

scholarly journals On the optimal control of coronavirus (2019-nCov) mathematical model; a numerical approach

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
N. H. Sweilam ◽  
S. M. Al-Mekhlafi ◽  
A. O. Albalawi ◽  
D. Baleanu
Keyword(s):  
Mathematical Model ◽  
Optimal Control ◽  
Weighted Average ◽  
Necessary Optimality Conditions ◽  
Numerical Approach ◽  
Population Number ◽  
Infected People ◽  
The Stability ◽  
Novel Coronavirus ◽  
Theoretical Results

Abstract In this paper, a novel coronavirus (2019-nCov) mathematical model with modified parameters is presented. This model consists of six nonlinear fractional order differential equations. Optimal control of the suggested model is the main objective of this work. Two control variables are presented in this model to minimize the population number of infected and asymptotically infected people. Necessary optimality conditions are derived. The Grünwald–Letnikov nonstandard weighted average finite difference method is constructed for simulating the proposed optimal control system. The stability of the proposed method is proved. In order to validate the theoretical results, numerical simulations and comparative studies are given.

On the modulation of water waves on shear flows

1976 ◽  
Vol 347 (1651) ◽  
pp. 537-546 ◽  
Keyword(s):  
Water Waves ◽  
Multiple Scales ◽  
Method Of Multiple Scales ◽  
Vries Equation ◽  
Harmonic Wave ◽  
Short Wave ◽  
Long Wave ◽  
Stokes Waves ◽  
The Stability ◽  
Wave Limit

The method of multiple scales is used to examine the slow modulation of a harmonic wave moving over the surface of a two dimensional channel. The flow is assumed inviscid and incompressible, but the basic flow takes the form of an arbitrary shear. The appropriate nonlinear Schrödinger equation is derived with coefficients that depend, in a complicated way, on the shear. It is shown that this equation agrees with previous work for the case of no shear; it also agrees in the long wave limit with the appropriate short wave limit of the Korteweg-de Vries equation, the shear being arbitrary. Finally, it is remarked that the stability of Stokes waves over any shear can be examined by using the results derived here.

scholarly journals Attenuation of Cross-Flow Fan Noise Using Porous Stabilizers

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Huanxin Lai ◽  
Meng Wang ◽  
Chuye Yun ◽  
Jin Yao
Keyword(s):  
Cross Flow ◽  
Sound Radiation ◽  
Internal Flow ◽  
Considerable Effect ◽  
Front Wall ◽  
Performance Curve ◽  
Fan Noise ◽  
Aerodynamic Performances ◽  
The Cross ◽  
Cross Flow Fan

This paper presents a qualitative analysis of controlling the cross-flow fan noise by using porous stabilizers. The stabilizer was originally a folded plate. It is changed into a porous structure which has a plenum chamber and vent holes on the front wall. In order to investigate the influences of using the porous stabilizers, experiments are carried out to measure the cross-flow fan aerodynamic performances and sound radiation. Meanwhile, the internal flow field of the fan is numerically simulated. The results show that the porous stabilizers have not produced considerable effect on the cross-flow fan's performance curve, but the noise radiated from the fan is strongly affected. This indicates the feasibility of controlling the cross-flow fan noise by using the porous stabilizers with selected porosity.

A Numerical Approach for the Simulation of Internal Nozzle Flow in a Pressure Swirl Atomizer Using Different Turbulent Models and Towards an Effective Inlet Weber Number

2013 ◽  
Author(s):  
Ahmadreza Abbasi Baharanchi ◽  
Seckin Gokaltun ◽  
Shahla Eshraghi
Keyword(s):  
Weber Number ◽  
Computational Cost ◽  
Internal Flow ◽  
Numerical Approach ◽  
Reynolds Stress Model ◽  
Multiphase Model ◽  
Vof Model ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

VOF Multiphase model is used to simulate the flow inside a pressure-swirl-atomizer. The capability of the Reynolds Stress Model and variants of the K-ε and K-ω models in modeling of turbulence has been investigated in the commercial computational fluid dynamics (CFD) software FLUENT 6.3. The Implicit scheme available in the volume-of-fluid (VOF) model is used to calculate the interface representation between phases. The atomization characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. The numerical results have been successfully validated against experimental data available for the computed parameters. The performance of the RNG K-ε model was found to be satisfactory in reducing the computational cost and introducing an effective Weber number for the flow simulated in this study.

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