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.

On the Dynamics and Stability of Cylindrical Shells Conveying Inviscid or Viscous Fluid in Internal or Annular Flow

1991 ◽  
Vol 113 (3) ◽  
pp. 409-417 ◽  
Author(s):  
A. El Chebair ◽  
A. K. Misra
Keyword(s):  
Annular Flow ◽  
Stokes Equations ◽  
Dynamical Behavior ◽  
Internal Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fluid Forces ◽  
Viscous Forces ◽  
The Fourier Transform ◽  
The Stability

This paper investigates theoretically for the first time the dynamical behavior and stability of a simply supported shell located coaxially in a rigid cylindrical conduit. The fluid flow is incompressible and the fluid forces consist of two parts: (i) steady viscous forces which represent the effects of upstream pressurization of the flow; (ii) unsteady forces which could be inviscid or viscous. The inviscid forces were derived by linearized potential flow theory, while the viscous ones were derived by means of the Navier-Stokes equations. Shell motion is described by the modified Flu¨gge’s shell equations. The Fourier transform technique is employed to formulate the problem. First, the system is subjected only to the unsteady inviscid forces. It is found that increasing either the internal or the annular flow velocity induces buckling, followed by coupled mode flutter. When both steady viscous and unsteady inviscid forces are applied, for internal flow, the system becomes stabilized; while for annular flow, the system loses stability at much lower velocities. Second, the system is only subjected to the unsteady viscous forces. Calculations are only performed for the internal flow case. The results are compared to those of inviscid theory. It is found that the effects of unsteady viscous forces on the stability of the system are very close to those of unsteady inviscid forces.

Stability of a Supported Cylinder in Axial Flow

2011 ◽  
Vol 117-119 ◽  
pp. 295-298
Author(s):  
Ji Duo Jin ◽  
Ning Li
Keyword(s):  
Numerical Analysis ◽  
Numerical Method ◽  
Dynamical Behavior ◽  
Axial Flow ◽  
Analytical Form ◽  
Viscous Force ◽  
Nonlinear Force ◽  
The Stability ◽  
Parameter Values ◽  
Zero Equilibrium

The stability of a supported cylinder subjected to axial flow is studied numerically. The dynamics of the cylinder is investigated with the numerical method applying the new nonlinear model in witch the nonlinear terms considered are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using three-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder. Some integration terms that appear in the discretization of the equation and can not be expressed in an analytical form are calculated using a numerical method. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence and at a higher velocity the flutter around the zero equilibrium may occur. There is some region in witch three different motions (configurations) can take place at the same parameter values.

Study on the Influence of Self-Circulating and Slot Combined Casing Treatment on the Stability of Transonic Compressor

2020 ◽  
Author(s):  
Song Yan ◽  
WuLi Chu ◽  
Zhengjing Shen
Keyword(s):  
Axial Flow ◽  
Internal Flow ◽  
Simulation Method ◽  
Tip Clearance ◽  
Single Type ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Blade Tip ◽  
The Stability ◽  
Stability Effect

Abstract Casing treatment (CT) has proven to be an effective way to enhance stability, and has a very important role in enhancing the stability of the compressor. Researchers have made great achievements and progress in the study of single-type CT structure, but less research on combined-type CT structure. In this paper, the isolated rotor of a high-load axial-flow compressor is taken as the research object, and the numerical simulation method is used to study the enhancing stability mechanism of the combined-type casing treatment (ASCT) by combining the axial slot casing treatment (ASC) and the self-circulating casing treatment (SCT). The study found that the reasonable choice of the ASCT scheme can make the enhancing stability effect of the ASCT higher than that of the single-type CT structure scheme. Through detailed quantitative analysis of the rotor’s internal flow field, it was found that ASC and SCT can suction the airflow downstream of the rotor passage, and then spray it into the main flow from the upstream of the rotor passage, and the blade tip blockage is reduced, the flow capacity of the blade tip passage is improved, and the rotor stability is enhanced by suppressing tip clearance leakage flow. The ASCT has both the spraying effect of the ASC and the SCT, and has the best improvement effect on the flow blockage zone in the rotor passage, and the obtained enhancing stability effect is also best. In addition, the circulation and re-injection of the airflow after CT has aggravated the flow blending loss in the blade tip zone, which has reduced the rotor efficiency. The ASCT has both the characteristics of the effect of the ASC and the SCT on the rotor efficiency, resulting in a large reduction in the rotor efficiency after using the ASCT.

Influence of Geometric Parameters on Annular Fluid Seal Characteristics

1995 ◽  
Author(s):  
Olivier Bonneau ◽  
Victor Lucas ◽  
Jean Frene
Keyword(s):  
Dynamical Behavior ◽  
Axial Flow ◽  
Difficult Problem ◽  
Geometric Parameters ◽  
Space Technology ◽  
Loss Parameter ◽  
The Stability ◽  
Energy Products ◽  
Geometrical Defects ◽  
Conical Seal

Abstract The numerical prediction of the dynamical behavior of turbopumps is very important. The space technology and the field of energy products are in constant development and it is necessary to quantify the influence of each component. The dynamical characteristics of annular seals must be calculated with accuracy. The aim of this work is to quantify the influence of geometric parameters on the dynamical behavior of the shaft. Three parameters will be studied: the duct loss parameter (at the seal entrance), a conical seal, and a misaligned seal. The two last geometrical defects have a direct influence on the film thickness. It is important to insist on the influence of the entrance duct loss which governs, in large part, the stiffness calculus (and then the stability). The most difficult problem is to evaluate this duct loss which depends on the seal geometry, Reynolds number and fluid characteristics... This study shows the important rôle played by geometrical parameter of a seal. The conicity and the misalignment modify the dynamical behavior of the shaft. These effects are essentially due to the axial flow which generates a pressure field due to axial film geometry. It should be noted that in the case of predominant circumferential flow these conclusions are totally different.

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.

scholarly journals Experience With the Development of an Euler Code for Rotor Rows

1983 ◽  
Author(s):  
J. P. Nenni ◽  
W. J. Rae
Keyword(s):  
Axial Flow ◽  
Internal Flow ◽  
Implicit Time ◽  
Internal Flows ◽  
Approximate Factorization ◽  
Kutta Condition ◽  
Method Of Solution ◽  
Time Marching ◽  
Flow Through ◽  
Marching Scheme

An Euler code for the transonic flow through an axial flow rotor has been developed. The method of solution is an implicit time marching scheme and approximate factorization has been used to minimize the computations. Although the basic methods have been well publicized in the external aerodynamics literature, several modifications were found to be crucial in order to apply the methods to internal flows. the internal flow calculations appear to be much more susceptible to instabilities than the external flow calculations. A boundary-fitted coordinate system is used which is an adaptation of one due to Ives. The calculation of the metrics of the transformation proves to be extremely important and a revision of the numerical viscosity treatment enlarges and enhances the domain where converged solutions can be obtained. In particular, it was found that the metrics must be discretized in the same spatial fashion as the governing partial differential equation in order to avoid introducing source-like terms which would quickly destroy the solution. Results are presented for the two-dimensional case of flows through a cascade with inlet Mach numbers up to 0.76 and with outlet conditions prescribed and with a Kutta condition applied.

scholarly journals Vibration of Slender Structures Subjected to Axial Flow or Axially Towed in Quiescent Fluid

2009 ◽  
Vol 2009 ◽  
pp. 1-19 ◽  
Author(s):  
L. Wang ◽  
Q. Ni
Keyword(s):  
Dynamical Behavior ◽  
Axial Flow ◽  
Axial Direction ◽  
Motion Constraints ◽  
Curved Pipes ◽  
Pipes Conveying Fluid ◽  
External Flows ◽  
Conveying Fluid ◽  
Quiescent Fluid ◽  
Slender Structures

The vibrations and stability of slender structures subjected to axial flow or axially towed in quiescent fluid are discussed in this paper. A selective review of the research undertaken on it is presented. It is endeavoured to show that slender structures subjected to axial flow or axially towed in quiescent fluid are capable of displaying rich dynamical behavior. The basic dynamics of straight and curved pipes conveying fluid (with or without motion constraints), carbon nanotubes conveying fluid, tubular beams subjected to both internal and external flows in axial direction, slender structures in axial flow or axially towed in quiescent fluid, cylindrical shells conveying or immersed in axial flow, solitary plate or parallel-plate assembly in axial flow; linear, nonlinear, and chaotic dynamics; these and many more are some of the aspects of the problem considered.

Nonlinear Dynamics of a Slender Flexible Cylinder in Axial Flow

2011 ◽  
Vol 130-134 ◽  
pp. 761-765
Author(s):  
Ji Duo Jin ◽  
N. Li ◽  
Zhao Hong Qin
Keyword(s):  
Nonlinear Dynamics ◽  
Flow Velocity ◽  
Nonlinear Model ◽  
Dynamic Instability ◽  
Dynamical Behavior ◽  
Axial Flow ◽  
Viscous Force ◽  
Flexible Cylinder ◽  
Flutter Instability ◽  
The Stability

The stability and nonlinear dynamics are studied for a slender flexible cylinder subjected to axial flow. A nonlinear model is presented, based on the corresponding linear equation of motion, for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the additional axial force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain, with this relatively simple nonlinear model, the flutter instability found in experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the buckled configuration becomes unstable at higher flow leading to post-divergence flutter. As the flow velocity increases further, the system is restabilized in the buckled configuration prior to another dynamic instability at higher flow.

Nonlinear Dynamics of Supported Cylinder Subjected to Axial Flow

2011 ◽  
Vol 243-249 ◽  
pp. 4712-4717
Author(s):  
Ji Duo Jin ◽  
Zhao Hong Qin
Keyword(s):  
Nonlinear Dynamics ◽  
Flow Velocity ◽  
Nonlinear Model ◽  
Dynamical Behavior ◽  
Axial Flow ◽  
Equation Of Motion ◽  
Flexible Cylinder ◽  
Chaotic Motions ◽  
Flutter Instability ◽  
The Stability

In this paper, the stability and nonlinear dynamics are studied for a slender flexible cylinder subjected to axial flow. A nonlinear model is presented, based on the corresponding linear equation of motion, for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are only the additional axial force induced by the lateral motions of the cylinder. Using six-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain, with this relatively simple nonlinear model, the flutter instability found in experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the new equilibrium (the buckled configuration) becomes unstable at higher flow leading to post-divergence flutter. As the flow velocity increases further, the quasiperiodic motion around the buckled position occurs, and this evolves into chaotic motions at higher flow.

Dynamics of a Supported Cylinder in Axial Flow

2011 ◽  
Vol 99-100 ◽  
pp. 1059-1062
Author(s):  
Ji Duo Jin ◽  
Ning Li ◽  
Zhao Hong Qin
Keyword(s):  
Nonlinear Dynamics ◽  
Numerical Analysis ◽  
Numerical Simulations ◽  
Nonlinear Model ◽  
Dynamical Behavior ◽  
Axial Flow ◽  
Viscous Force ◽  
Friction Drag ◽  
Flutter Instability ◽  
Nonlinear Force

The nonlinear dynamics are studied for a supported cylinder subjected to axial flow. A nonlinear model is presented for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain the flutter instability found in the experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the new equilibrium (the buckled configuration) becomes unstable at higher flow leading to post-divergence flutter. The effect of the friction drag coefficients on the behavior of the system is investigated.

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