Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 2: Experiments

1979 ◽  
Vol 46 (1) ◽  
pp. 52-57 ◽  
Author(s):  
M. J. Hannoyer ◽  
M. P. Paidoussis
Keyword(s):  
Axial Flow ◽  
Internal Flow ◽  
Quantitative Agreement ◽  
External Flow ◽  
Critical Conditions ◽  
Experimental Program ◽  
Water Tunnel ◽  
Elastic Instabilities ◽  
Theoretical Predictions ◽  
Flow Part

This paper describes the experimental program which was conducted in parallel with the theoretical investigation presented in Part 1 of this study. Experiments were conducted in a special water tunnel with silicone rubber cantilevers which, in the case of external flow, were truncated cones, the free ends of which were streamlined; in the case of internal flow the beams were tubular, conical inside, and either conical or cylindrical outside, immersed either in still air or water. Experiments were also conducted with uniform tubular cylinders, and some with simultaneous internal and external axial flow. Qualitatively these experiments support theoretical predictions very well. The critical conditions for the various fluid-elastic instabilities which these systems can develop were measured and compared with theory. Quantitative agreement ranged from excellent to fair, the former for internal flow in conical tubes, and the latter for very slender cones in external flow.

Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 1: Theory

1979 ◽  
Vol 46 (1) ◽  
pp. 45-51 ◽  
Author(s):  
M. J. Hannoyer ◽  
M. P. Paidoussis
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Thickness ◽  
Equations Of Motion ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
High Flow ◽  
Flow Passage ◽  
Flow Part ◽  
Surrounding Fluid

This paper develops a general theory for the dynamics of slender, nonuniform axisymmetric beams subjected to either internal or external flow, or to both simultaneously. The effect of the boundary layer of the external flow is taken into account in the formulation. Typical solutions of the equations of motion are presented for cantilevered conical beams in external flow and for beams with a conical internal flow passage. Such systems lose stability at sufficiently high flow velocity, internal or external, either by flutter or by buckling. The effect of several parameters is investigated. For internal flow, the internal and external shape, whether uniform or conical, and the density of the surrounding fluid have sometimes unexpected effects on stability; e.g., tubular beams lose stability at lower internal flow when immersed in water than when in air. For external flow the effects of conicity, free end shape and boundary-layer thickness are investigated; the latter has a strong stabilizing influence, such that simple theory neglecting this effect results in serious error.

Nonlinear Dynamics of an Extensible Flexible Pipe Conveying Fluid and Subjected to External Axial Flow

2011 ◽  
Author(s):  
F. A. Ghaith ◽  
Y. A. Khulief
Keyword(s):  
Nonlinear Equations ◽  
Linear Models ◽  
Numerical Solutions ◽  
Plug Flow ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Pipe Conveying Fluid ◽  
Flexible Pipe ◽  
Conveying Fluid

In this paper, the nonlinear equations representing the dynamics of a slender flexible pipe conveying fluid and subjected to external axial flow are formulated using the extended Hamilton’s principle. The internal flow is assumed to be steady, fully developed turbulent and approximated by a plug flow, while the external flow is represented by the induced hydrodynamic forces associated with friction, hydrostatic and inviscid components. The pipe centerline is considered to be extensible, and hence two coupled nonlinear equations of motion associated with longitudinal and transverse displacements are derived to describe the dynamics of the system. The developed model takes into account the fluid pressurization force and the tension in the pipe, which may be externally applied or associated with the frictional forces. For verification purpose, comparisons were performed, wherein the developed formulation was reduced to some published linear models. Numerical solutions were obtained for a case study of a double-pipe heat exchanger, wherein the effects of internal flow, external flow, flowrate, and radial gap on the dynamic characteristics of the system were addressed.

Dynamics of flexible slender cylinders in axial flow Part 1. Theory

1966 ◽  
Vol 26 (4) ◽  
pp. 717-736 ◽  
Author(s):  
M. P. Paidoussis
Keyword(s):  
Axial Flow ◽  
Cylindrical Body ◽  
Critical Conditions ◽  
Hydrodynamic Drag ◽  
System Parameters ◽  
Flow Part ◽  
Frictional Forces ◽  
Conditions Of Stability ◽  
Large Flow ◽  
Oscillatory Instabilities

A general theory is presented to account for the small, free, lateral motions of a flexible, slender, cylindrical body immersed in fluid flowing parallel to the position of rest of its axis. The cylinder is either clamped or pinned at both ends, or clamped at the upstream end and free at the other; it lies in a horizontal plane wherein all motion is considered to be confined. It is shown that for sufficiently large flow velocities the cylinder may be subject to buckling and oscillatory instabilities in its first and higher flexural modes, respectively. It is shown that for cylinders with both ends supported the oscillatory instabilities are specifically caused by lateral frictional forces, and that in the absence of hydrodynamic-drag effects only buckling is possible. The same applies for cylinders supported at the upstream end and with a very long, gradually tapering free end. The critical conditions of stability, expressed in dimensionless form, are evaluated extensively for clamped-free and pinned-pinned cylinders, illustrating the effect of the various system parameters on stability.

Experiments on vertical slender flexible cylinders clamped at both ends and subjected to axial flow

2007 ◽  
Vol 366 (1868) ◽  
pp. 1275-1296 ◽  
Author(s):  
Y Modarres-Sadeghi ◽  
M.P Païdoussis ◽  
C Semler ◽  
E Grinevich
Keyword(s):  
Axial Flow ◽  
Quantitative Agreement ◽  
Dynamical Behaviour ◽  
High Flow ◽  
The Third ◽  
Theoretical Predictions ◽  
Series Of Experiments ◽  
Linear And Nonlinear ◽  
Theory And Experiment ◽  
Flow Velocities

Three series of experiments were conducted on vertical clamped–clamped cylinders in order to observe experimentally the dynamical behaviour of the system, and the results are compared with theoretical predictions. In the first series of experiments, the downstream end of the clamped–clamped cylinder was free to slide axially, while in the second, the downstream end was fixed; the influence of externally applied axial compression was also studied in this series of experiments. The third series of experiments was similar to the second, except that a considerably more slender, hollow cylinder was used. In these experiments, the cylinder lost stability by divergence at a sufficiently high flow velocity and the amplitude of buckling increased thereafter. At higher flow velocities, the cylinder lost stability by flutter (attainable only in the third series of experiments), confirming experimentally the existence of a post-divergence oscillatory instability, which was previously predicted by both linear and nonlinear theory. Good quantitative agreement is obtained between theory and experiment for the amplitude of buckling, and for the critical flow velocities.

An Experimental and Analytical Study of Vortex-Flow Temperature Separation by Superposition of Spiral and Axial Flow: Part 2

1959 ◽  
Vol 81 (3) ◽  
pp. 213-221 ◽  
Author(s):  
J. E. Lay
Keyword(s):  
Analytical Study ◽  
Vortex Motion ◽  
Axial Flow ◽  
Experimental Program ◽  
Stagnation Temperature ◽  
Spiral Flow ◽  
Free Vortex ◽  
Temperature Separation ◽  
Flow Part

Part 2 reports on the analytical study. The free vortex motion of the gas upon entrance to the tube is mathematically superposed to a compressible sink to give a spiral flow in the plane. The characteristic existence of limit circles is corroborated by the experimental flow visualization. The solution in space is obtained by addition of a uniform axial velocity to the spiral flow. When viscosity effects are considered, the free vortex is shown to change into a forced vortex. The latter flow is one of minimum kinetic energy and maximum entropy. Energy considerations enable the determination of an optimum cold air radius to give largest stagnation temperature separation. Significantly, this was the radius that gave best performance in the experimental program.

scholarly journals Design and Verification for Hypersonic Aerodynamic Model with Duct of Internal and External Flow Decoupling

2015 ◽  
Vol 9 (12) ◽  
pp. 202
Author(s):  
Zejiang Wang ◽  
Wenping Song ◽  
Jin Jiang ◽  
Huiyong Zhao ◽  
Yong Zhang
Keyword(s):  
Circular Cross Section ◽  
Wind Tunnel Test ◽  
Internal Flow ◽  
Test System ◽  
External Flow ◽  
Design Technique ◽  
Aerodynamic Model ◽  
Component Strain ◽  
Flow Part ◽  
Key Techniques

<p class="zhengwen"><span lang="EN-GB">In order to develop the design techniques for the hypersonic aerodynamic testing model with duct system of internal flow and external flow decoupling, this research used a circular cross section air-breathing hypersonic cruise vehicle model, explored the model design technique for internal flow and external flow separated from each other, the design technique and the seal technique for the clearance between the internal flow part and the external flow part, the design technique of ring type six-component strain-gauge balance and so on. A wind tunnel test was conducted at mach 6. The results of the test indicate that, the design of the internal flow and external flow decoupling test system is successful to get credible test data. It have been mastered that the key techniques for the test system design of internal flow and external flow decoupling.</span></p>

Combinational Influence of Internal Flow and External Annular Axial Flow on Instability of Cantilevered Double Wall Pipes

2017 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Akinori Moriasa
Keyword(s):  
Dynamic Stability ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Elastic Tube ◽  
Piping System ◽  
Navier Stokes Equation ◽  
Double Wall

When flexible pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In this paper, the pipe is subjected to internal flow and external flow at the same time. The dynamic stability of a double wall pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures for the development of a piping system in the field of ocean mining, and in the field of fluid energy generation, and so on. In this paper, the pipe structures are assumed to be composed of the cantilevered elastic tube structure. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence are added to are applied. Changing the flow direction and the fluid velocity as for the internal flow and the external flow, the dynamic stability of the double wall pipes is investigated and discussed. Moreover, changing the flow rate and the density of a fluid and a structure, these effects on the stability of double wall pipes are investigated.

Stability of Cantilevered Pipes Subjected to Internal Flow and External Annular Axial Flow Simultaneously

2015 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Akinori Moriasa
Keyword(s):  
Flow Direction ◽  
Fluid Velocity ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Energy Utilization ◽  
Navier Stokes ◽  
Piping System ◽  
Navier Stokes Equation ◽  
Cantilevered Beam

When slender pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In the development of a piping system in the field of ocean mining, and in the field of fluid energy utilization, and so forth, the double walled pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures. In this paper, the pipe structures are assumed to be composed of the cantilevered beam structure which shows the complicated dynamic behavior than the other supported conditions. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence is added to are applied. Changing the flow direction and the fluid velocity of the internal flow and the external flow, and the specifications of modeling, the stability of the double walled pipes is investigated and discussed.

The propagation of gravity currents in a V-shaped triangular cross-section channel: experiments and theory

2014 ◽  
Vol 754 ◽  
pp. 232-249 ◽  
Author(s):  
Marius Ungarish ◽  
Catherine A. Mériaux ◽  
Cathy B. Kurz-Besson
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Viscosity Coefficient ◽  
Gravity Currents ◽  
Quantitative Agreement ◽  
Flat Bottom ◽  
Special Configuration ◽  
Theoretical Predictions ◽  
Speed Of Propagation ◽  
High Reynolds

AbstractWe investigate the motion of high-Reynolds-number gravity currents (GCs) in a horizontal channel of V-shaped cross-section combining lock-exchange experiments and a theoretical model. While all previously published experiments in V-shaped channels were performed with the special configuration of the full-depth lock, we present the first part-depth experiment results. A fixed volume of saline, that was initially of length $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}x_0$ and height $h_0$ in a lock and embedded in water of height $H_0$ in a long tank, was released from rest and the propagation was recorded over a distance of typically $ 30 x_0$. In all of the tested cases the current displays a slumping stage of constant speed $u_N$ over a significant distance $x_S$, followed by a self-similar stage up to the distance $x_V$, where transition to the viscous regime occurs. The new data and insights of this study elucidate the influence of the height ratio $H = H_0/h_0$ and of the initial Reynolds number ${\mathit{Re}}_0 = (g^{\prime }h_0)^{{{1/2}}} h_0/ \nu $, on the motion of the triangular GC; $g^{\prime }$ and $\nu $ are the reduced gravity and kinematic viscosity coefficient, respectively. We demonstrate that the speed of propagation $u_N$ scaled with $(g^{\prime } h_0)^{{{1/2}}}$ increases with $H$, while $x_S$ decreases with $H$, and $x_V \sim [{\mathit{Re}}_0(h_0/x_0)]^{{4/9}}$. The initial propagation in the triangle is 50 % more rapid than in a standard flat-bottom channel under similar conditions. Comparisons with theoretical predictions show good qualitative agreements and fair quantitative agreement; the major discrepancy is an overpredicted $u_N$, similar to that observed in the standard flat bottom case.

Improvement of Stalling Characteristics of an Axial-Flow Fan by Radial-Vaned Air-Separators

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nobuyuki Yamaguchi ◽  
Masayuki Ogata ◽  
Yohei Kato
Keyword(s):  
Solid Wall ◽  
Axial Flow ◽  
Internal Flow ◽  
Rotor Blades ◽  
Relative Location ◽  
Flow Conditions ◽  
Axial Flow Fan ◽  
Light Load ◽  
Stall Prevention ◽  
Air Separator

An improved construction of air-separator device, which has radial-vanes embedded within its inlet circumferential opening with their leading-edges facing the moving tips of the fan rotor-blades so as to scoop the tip flow, was investigated with respect to the stall-prevention effect on a low-speed, single-stage, lightly loaded, axial-flow fan. Stall-prevention effects by the separator layout, relative location of the separator to the rotor-blades, and widths of the openings of the air-separator inlet and exit were parametrically surveyed. As far as the particular fan is concerned, the device together with the best relative location has proved to be able to eliminate effectively the stall zone having existed in the original solid-wall characteristics, which has confirmed the promising potential of the device. Guidelines were obtained from the data for optimizing relative locations of the device to the rotor-blades, maximizing the stall-prevention effect of the device, and minimizing the axial size of the device for a required stall-prevention effect, at least for the particular fan and possibly for fans of similar light-load fans. The data suggest the changing internal flow conditions affected by the device conditions.

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