Cylinder In Axial Flow Research Articles

An analytical model for vibration of clusters of flexible cylinders in turbulent axial flow

This paper describes an analytical model for the flow-induced vibration of clusters of cylinders in axial flow, in the sub-critical flow regime (i.e., at flow velocities below the threshold for fluid-elastic instabilities). The vibration is excited by the random pressure fluctuations in the turbulent flow acting on the cylinders. Correlation of the excitation field is assumed to exist, with appropriate length scales, not only on the same cylinder, but also on adjacent cylinders in the cluster. In the absence of measured correlation functions for the system at hand, numerical calculations were conducted with available pipe-flow correlation functions, due to Bakewell et al., assumed to be approximately valid. Power- and cross-spectral densities of the vibration are presented, as well as r.m.s. amplitudes, for simple systems of two, three and four cylinders, and the characteristics of the flow-induced vibration are then discussed. It is seen that there is remarkable qualitative agreement with measured characteristics of vibration.

Experiments on vibration of clusters of cylinders in axial flow: Modal and spectral characteristics

This paper describes experiments on axial-flow-induced lateral vibration of clustered circular cylinders, in which most attention is devoted to the modal characteristics of the measured vibration and its spectral content. The majority of tests have been conducted with symmetric clusters of four flexible cylinders in a water tunnel. One or two or the cylinders were instrumented with embedded strain gauges, permitting measurement of vibration in two mutually perpendicular planes of motion. Both modal and spectral characteristics have been found to agree remarkably well with those predicted by a previously developed theory for the free-vibration characteristics of the system.

The thick turbulent boundary layer on a long fine cylinder in axial flow

SummaryTransverse curvature effects in axi-symmetric flow on a circulai cylinder are discussed and it is deduced that for small δ/a, where δ is the boundary layer thickness and a is the cylinder radius, transverse curvature effects are small, for δ/a = 0(1) the effect is felt mainly in the outer region and for δ/a » 1, both the inner and the outer regions are affected. It is argued that the last case can only be achieved experimentally in the laboratory if the radius Reynolds number Ra= U1a/v is small and the streamwise Reynolds number Rx=U1xlv is large, implying x/a large. New experimental data are presented for this case. The data show that both the mean and turbulent flow field scale on outer variables throughout the layer and, for Ra≥455, exhibit Reynolds number independence. No logarithmic region is found in the mean profiles, a result which is echoed by the absence of a shoulder in the streamwise turbulence profiles which clearly evidence that the flow in the layer is fully turbulent. A flow model is suggested, in physical terms, to explain the very high turbulence levels found close to the cylinder at values of Ra which should, according to stability theory, be bordering on laminar flow.

Parametric Resonance Oscillations of Flexible Slender Cylinders in Harmonically Perturbed Axial Flow—Part 2: Experiments

This paper examines experimentally the dynamical behavior of a flexible slender cylinder in axial flow, perturbed harmonically in time. Parametric resonance oscillations were found to exist over certain ranges of frequencies and amplitudes of flow-velocity perturbations. The most prominent of the resonances, in these experiments, were associated with the second-mode principal primary resonance, and were studied extensively. Agreement with theory was found to be quite good.

Closure to “Discussion of ‘An Experimental Study of the Flow-Induced Motions of a Flexible Cylinder in Axial Flow’” (1980, ASME J. Fluids Eng., 102, p. 119)

Closure to “Discussion of ‘An Experimental Study of the Flow-Induced Motions of a Flexible Cylinder in Axial Flow’” (1980, ASME J. Fluids Eng., 102, p. 119)

The dynamics of clusters of flexible cylinders in axial flow: Theory and experiments

This paper presents an outline of the theory for the dynamics of clusters of independently supported flexible cylinders in axial flow, and an extensive discussion of the behaviour of such systems with increasing flow velocity, with special emphasis placed on the modal forms of free coupled motions of the cylinders and on the onset of instabilities. Results of an experimental study of the problem are also presented, involving systems of two, three or four cylinders supported at both ends and positioned symmetrically in the cylindrical test section of a water tunnel; experiments were conducted with different inter-cylinder gaps and support conditions. Both theory and experiment show that with increasing flow the system loses stability by buckling in one of its coupled modes, commonly in a pattern where cylinders move towards one another symmetrically, maximum displacement occurring just downstream of their midpoints. With increasing flow, theory predicts that other buckling instabilities are superimposed on the first; in the experiments the system remains buckled, changing modal patterns constantly; some of them correspond to those predicted by theory. At sufficiently high flow, oscillatory motion is observed, corresponding to theoretical flutter. Theory and experiment agree qualitatively in most essential features of the dynamical behaviour of the system, and quantitative agreement in the critical flow velocities for the onset of the first buckling instability is remarkably good.

Closure to “Discussions of ‘An Experimental Study of the Flow-Induced Motions of a Flexible Cylinder in Axial Flow’” (1979, ASME J. Fluids Eng., 101, pp. 292–293)

Closure to “Discussions of ‘An Experimental Study of the Flow-Induced Motions of a Flexible Cylinder in Axial Flow’” (1979, ASME J. Fluids Eng., 101, pp. 292–293)

An Experimental Study of the Flow-Induced Motions of a Flexible Cylinder in Axial Flow

Experimental studies of the flow-induced lateral motions of a flexible tube in parallel flow are reported. The experiments were conducted in a 19.05 cm diameter test section of a blow-down type water tunnel. The flexible member, 1.59 cm in diameter and 7.92 m long, was fixed at the upstream end and free at the downstream end and was approximately neutrally buoyant. A fully-developed annular flow was realized in the test section. Photographs established the dependence of the flow-induced lateral motions on the mechanical properties, the flow velocity, and tension in the flexible member. Spectral analysis of the continuously-monitored data from an optical displacement sensor showed that the flow-induced lateral motions of the flexible member can be described as limited-band, stationary random processes. The maximum of the power spectral density shifted slightly as the flow velocity increased. The amplitude of the power spectrum attenuated rapidly with distance from the free downstream extremity of the cylinder.

Comment on ' 'Turning Moment on a Rotating Disk"

Paidoussis, M.P., Dynamics of Tubular Cantilevers Conveying Fluid, Journal of Mechanical Engineering Science, Vol. 12, No. 2, 1970, pp. 85-103. Lighthil l , M.J. , Hydromechanics of Aquatic Animal Propulsion, Annual Review of Fluid Mechanics, Vol. 1, 1969, pp. 413-446. Paidoussis, M.P., Dynamics of Flexible Slender Cylinders in Axial Flow. Part 1. Theory, Journal of Fluid Mechanics, Vol. 26, Part 4, 1966, pp. 717-736. Granville, P. S., The Torque and Turbulent Boundary Layer for Rotating Disks with Smooth and Rough Surfaces, and in DragReducing Polymer Solutions, Journal of Ship Research, Vol. 17. Dec. 1973, pp. 181-195.

Experiments on Relatively Thick Turbulent Boundary Layers on Rotating Cylinders in Axial Flow : 2nd Report, The Flows under Pressure Gradients

Experiments on Relatively Thick Turbulent Boundary Layers on Rotating Cylinders in Axial Flow : 2nd Report, The Flows under Pressure Gradients

Thick Turbulent Boundary Layers on Rotating Cylinders in Axial Flow : 1st Report, The Effect of a Roughness Element

Thick Turbulent Boundary Layers on Rotating Cylinders in Axial Flow : 1st Report, The Effect of a Roughness Element

Stability of flexible slender cylinders in pulsatile axial flow

A theoretical analysis is presented of the dynamical behaviour of flexible cylinders in axial flow, the velocity of which is perturbed harmonically in time. It is found that parametric instabilities are possible for certain ranges of frequencies and amplitudes of the perturbations. These instabilities occur over specific ranges of flow velocities, and in the case of cantilevered cylinders are associated with only some of the modes of the system.

Mechanics of transition in an axisymmetric laminar boundary layer on a circular cylinder

Measurements of the growth of artificially generated turbulent spots and intermittency distribution in the transition region on a circular cylinder in axial flow show that the instability Reynolds number of 11,000 has a marked effect on the properties. In particular, it is found that the spot production in the initial region when a single turbulent spot has not yet wrapped around the cylinder and the propagation is essentially two-dimensional, is significantly altered. But the transition in the downstream or latter region, where most of the turbulent spots propagate onedimensionally (like the turbulent plugs in a pipe), is not affected. When the radius Reynolds number is more than 11,000, the intermittency law in the initial region is essentially the same as in twodimensional flow on a flat plate and in the latter region it is the one-dimensional flow in a pipe, the demarcation between the two regions being quite sharp.

Dynamics of cylindrical structures subjected to axial flow

A general theory is presented for the dynamics of slender cylindrical beams immersed in purely axial, uniform and steady flow. The cylinders may be either isolated or be part of a cluster of identical cylinders. Gravity and pressurization effects are taken into account. It is shown that small flow velocities damp free motions, but that at sufficiently high flow velocities hydroelastic instabilities are possible. Typically, pinned-pinned (simply supported) cylinders are subject to buckling in their first mode, and then at higher flow velocities in their second mode; at slightly higher flow velocities, coupled-mode flutter is shown to occur. Close spacing in a cluster severely destabilizes the system. Cantilevered cylinders, on the other hand, may be subject to buckling in their first mode and to flutter in their higher modes. Finally, the case of cylinders in axial flow subjected to an arbitrary force field is discussed, and a method is developed by which the response may be obtained.

Mean Velocity Profile of a Thick Turbulent Boundary Layer along a Circular Cylinder

The mean velocity profile of a turbulent boundary layer on a cylinder in axial flow without pressure gradient may be written, over some inner range of wall distances >', in the functional form l* = F(v*y/v>y/<*) 0) where u(x,y) denotes mean velocity, v+(x) friction velocity, v kinematic viscosity, and a cylinder radius. Within the viscous sublayer, apart from terms of order (y/a),' the explicit result for a laminar cylindrical boundary layer can be shown to apply and written as (2)

Dynamics of flexible slender cylinders in axial flow Part 2. Experiments

The experiments described here were designed to illustrate the dynamical behaviour of flexible cylinders in axial flow theoretically examined in Part 1. Rubber cylinders, either clamped or pinned at the upstream end and free at the other, or pinned at both ends, displayed both buckling and oscillatory instabilities when immersed in flowing water of sufficiently high velocity. The conditions of neutral stability were determined in a number of cases and compared with theory. The observations were in substantial agreement with the theory.

Incompressible laminar axisymmetric near wake behind a very slender cylinder in axial flow.

Abstract : An attempt is made to solve the near wake problem behind a very slender cylinder in axisymmetric incompressible laminar flow by a series expansion method. Although the solution thus found applies only up to a very limited distance downstream of the base, it exhibits important differences with the corresponding two-dimensional problem of the wake behind a flat plate, which are characteristic of the axisymmetry of the flow. This series expansion and an asymptotic expansion for the far wake region are compared with a simple solution obtained by linearizing the momentum equation. (Author)

Effect of Transverse Curvature on Turbulent-Boundary-Layer Characteristics

Tests made on the turbulent boundary layer on a circular cylinder in axial flow at zero pressure gradient are described. From the measurements, similarity laws of the velocity profile are formulated, and various boundary-layer characteristics are evaluated and compared with the flatplate results. It is found that the effect of transverse curvature is to increase the surface shearing stress and to decrease the boundary-layer thickness, and that the latter variation is more pronounced than the former.

Measurements of Turbulent Skin Friction on Cylinders in Axial Flow at Subsonic and Supersonic Velocities

Measurements of Turbulent Skin Friction on Cylinders in Axial Flow at Subsonic and Supersonic Velocities

Recent Investigation of Temperature Recovery and Heat Transmission on Cones and Cylinders in Axial Flow in the N.O.L. Aeroballistics Wind Tunnel

Recent Investigation of Temperature Recovery and Heat Transmission on Cones and Cylinders in Axial Flow in the N.O.L. Aeroballistics Wind Tunnel