A Study on Fluid Excitation Forces Acting on a Rotated Square Tube Bundle of T∕D=3.1 in Cross-Flow

2006 ◽  
Vol 129 (1) ◽  
pp. 162-168
Author(s):  
Fumio Inada ◽  
Kimitoshi Yoneda ◽  
Akira Yasuo ◽  
Takashi Nishihara
Keyword(s):  
Correlation Length ◽  
Vortex Shedding ◽  
Tube Bundle ◽  
Cross Flow ◽  
Axial Direction ◽  
Universal Curve ◽  
Power Spectral ◽  
Small Pitch ◽  
Vortex Shedding Frequency ◽  
Excitation Force

The local fluid excitation force acting on a rotated square tube bundle having transverse pitch-to-diameter ratio of T∕D=3.1, in a single-phase cross-flow was measured, and the normalized power spectral density (NPSD) and correlation length in the axial direction of a tube were examined. The fluid excitation force acting on the interior tube was from three to ten times larger than that acting on the upstream tube. The fluid force was almost fully developed after the third row. NPSD of the fluid excitation force could be almost plotted on a single universal curve. Regarding the lift direction, there was a peak in NPSD at fD∕u∼0.3 caused by vortex shedding. Regarding the drag direction, there could be another peak in NPSD around twice the vortex shedding frequency. In the region of fD∕u>0.5, where the effect of the vortex shedding was assumed to be small in the lift direction, the correlation length of the lift direction was ∼1.1D. NPSD was a little larger than previous results for tube bundles of relatively small pitch to diameter ratios summarized by Axisa, Antunes, and Villard (1990, J. Fluid Struct., 4, pp. 321–341).

Flow-Induced Vibration of Cross-Shaped Tube Bundle: The Effect of Tube Bundle Arrangement

2003 ◽  
Author(s):  
Fumio Inada ◽  
Takashi Nishihara ◽  
Akira Yasuo ◽  
Ryo Morita ◽  
Akihiro Sakashita ◽  
...  
Keyword(s):  
Correlation Length ◽  
Random Vibration ◽  
Tube Bundle ◽  
Cross Flow ◽  
Flow Induced Vibration ◽  
Power Spectral ◽  
Shaped Tube ◽  
Excited Vibration ◽  
Power Spectral Densities ◽  
Staggered Arrangement

A cross-shaped tube bundle is proposed for the lower plenum structure in the next-generation LWR. The effect of tube bundle arrangement on the flow-induced vibration characteristics of the cross-shaped tube bundle in cross flow was considered experimentally. Regarding random vibration, the power spectral density of the fluid force of the staggered arrangement as well as the correlation length was measured and those of the normal arrangement were compared with those of the staggered arrangement. Regarding self-excited vibration, vibration response was compared. The trend of the power spectral densities, correlation length, and the critical velocity of the normal arrangement were similar to those of the staggered arrangement.

Turbulence-Induced Fluid Dynamic Forces Acting on Cross-Shaped Tube Bundle in Cross Flow

2002 ◽  
Author(s):  
Takashi Nishihara ◽  
Fumio Inada ◽  
Akira Yasuo ◽  
Ryo Morita ◽  
Akihiro Sakashita ◽  
...  
Keyword(s):  
Tube Bundle ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Scale Model ◽  
Small Scale ◽  
Power Spectral ◽  
Shaped Tube ◽  
Dynamic Forces ◽  
Excitation Force ◽  
Small Scale Model

A cross-shaped tube bundle with dense arrangement may be designed for a lower plenum structure in a next generation LWR, though the characteristics of flow-induced vibration of this type of tube bundle remain virtually unknown. In this study, turbulence-induced fluid dynamic forces acting on a cross-shaped tube bundle with a dense arrangement subject to cross flow were measured by water tunnel tests with two types of scale models. One is a small-scale model to measure local fluid dynamic forces and their correlation length in the lift and drag direction. The other is a large-scale model to investigate the effect of the Reynolds number on fluid dynamic forces in the lift, drag and torsional directions. Free oscillation tests with another small-scale model were also conducted to measure vibration amplitude by random excitation force. In conclusion, the following results were obtained. Vortex-induced vibration cannot arise in the cross-shaped tube bundle, since a typical peak corresponding to periodic vortex shedding was not observed in power spectral density for fluid excitation force. Power spectral densities of fluid dynamic forces in the drag, lift and torsional directions have mutually similar properties and they are hardly dependent on the Reynolds number. The experimental results were compiled into dimensionless correlation equations composed of the power spectral density for the local fluid excitation force and its correlation length. They are useful for evaluating the random vibration amplitude. The estimated amplitudes of turbulence-induced vibration by the correlation equation coincide with those of the experimental results obtained by the free-oscillation tests.

Equivalent Diameter for Predicting Vortex Shedding of Finned Cylinders in Cross-Flow

2021 ◽  
Author(s):  
Mohammed Alziadeh ◽  
Atef Mohany
Keyword(s):  
Vortex Shedding ◽  
Tube Bundle ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Resonance Excitation ◽  
Equivalent Diameter ◽  
Frequency Scaling ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Abstract This article explores different equivalent diameter equations found in the literature for shedding frequency scaling and applying it to various types of finned cylinders in industrial heat exchangers. The focus is on three finned cylinder types: straight, twist-serrated, and crimped spirally finned cylinders. Within each finned cylinder category, at least three different finned cylinders are investigated. The results indicate that utilizing the appropriate equivalent diameter for vortex shedding frequency scaling collapses the data within the Strouhal bounds of a bare cylinder away from resonance excitation. However, the onset of flow-excited acoustic resonance and peak acoustic pressure in all the finned cylinder cases occur at a reduced flow velocity earlier than their equivalent diameter bare cylinder. This suggests that although utilizing the appropriate equivalent diameter can predict the shedding frequency away from resonance, it cannot be used in velocity scaling to predict the onset of acoustic resonance in finned tube bundle.

Computational Determination of the Modified Vortex Shedding Frequency for a Rigid, Truncated, Wall-Mounted Cylinder in Cross Flow

2014 ◽  
Author(s):  
Aimie Faucett ◽  
Todd Harman ◽  
Tim Ameel
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Classical Case ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
End Effects ◽  
Dimensional Solution ◽  
Horseshoe Vortices ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Flow around a rigid, truncated, wall-mounted cylinder with an aspect ratio of 5 is examined computationally at various Reynolds numbers Re to determine how the end effects impact the vortex shedding frequency. The existence of the wall and free end cause a dampening of the classical shedding frequency found for a semi-infinite, two-dimensional cylinder, as horseshoe vortices along the wall and flow over the tip entrain into the shedding region. This effect was observed for Reynolds numbers in the range of 50 to 2000, and quantified by comparing the modified Strouhal numbers to the classical (two-dimensional) solution for Strouhal number as a function of Reynolds number. The range of transition was found to be 220 < Re < 300, versus 150 < Re < 300 for the classical case. Vortex shedding started at Re ≈ 100, significantly above Re = 50, where shedding starts for the two-dimensional case.

Elastically Mounted Body in Cross Flow With an Attached Pendulum

1993 ◽  
Author(s):  
Aleš Tondl
Keyword(s):  
Vortex Shedding ◽  
Parametric Excitation ◽  
Trivial Solution ◽  
Cross Flow ◽  
Vertical Vibration ◽  
The Body ◽  
Autoparametric Resonance ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
The Stability

Abstract A pendulum is attached to an elastically mounted body in cross flow. The body is excited due to the action of vortex shedding. The stability of the semi-trivial solution (representing the vibration of the body with the non-oscillating pendulum) is investigated. It is proved that a certain interval of the vortex shedding frequency can exist where the semi-trivial solution representing the vertical vibration of the body is unstable. The body vibration is the source of parametric excitation of the pendulum resulting in autoparametric resonance.

An experimental study of steady and pulsating cross-flow over a semi-staggered tube bundle

2005 ◽  
Vol 219 (3) ◽  
pp. 283-298 ◽  
Author(s):  
E Konstantinidis ◽  
D Castiglia ◽  
S Balabani
Keyword(s):  
Experimental Study ◽  
Vortex Shedding ◽  
Considerable Increase ◽  
Tube Bundle ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Velocity Fields ◽  
Velocity Fluctuations ◽  
The Mean

This paper describes an experimental study of the cross-flow characteristics in a semi-staggered tube bundle for Reynolds numbers in the range 1100-12 900. It is shown that by displacing transversely the tubes in the even rows of an in-line bundle by one diameter the vortex-shedding mechanism is suppressed. Vortex shedding is re-established and reinforced by pulsations superimposed on to the approaching flow and a considerable increase in the power of the associated velocity fluctuations is observed in the bundle. Two cases of pulsating flow are examined with different effects on the flow structure of the bundle. Detailed measurements of the mean and fluctuating velocity fields in the semi-staggered tube bundle together with flow visualization images are also reported in the paper in order to examine in depth the effects of tube displacement and flow pulsations. Comparisons with in-line and staggered configurations having the same spacing-to-diameter ratios are made.

Free vibrations of two side-by-side cylinders in a cross-flow

2001 ◽  
Vol 443 ◽  
pp. 197-229 ◽  
Author(s):  
Y. ZHOU ◽  
Z. J. WANG ◽  
R. M. C. SO ◽  
S. J. XU ◽  
W. JIN
Keyword(s):  
Vortex Shedding ◽  
Natural Frequencies ◽  
Cross Flow ◽  
Free Vibrations ◽  
Dynamic Strain ◽  
Valuable Insight ◽  
Combined System ◽  
Sharp Variation ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Free vibrations of two side-by-side cylinders with fixed support (no rotation and displacement) at both ends placed in a cross-flow were experimentally investigated. Two fibre-optic Bragg grating sensors were used to measure the dynamic strain, while a hot wire and flow visualization were employed to examine the flow field around the cylinders. Three T/d ratios, 3.00, 1.70 and 1.13, were investigated, where T is the centre-to-centre cylinder spacing and d is the diameter; they give rise to three different flow regimes. The investigation throws new light on the shed vortices and their evolution. A new interpretation is proposed for the two different dominant frequencies, which are associated with the narrow and the wide wake when the gap between the cylinders is between 1.5 and 2.0 as reported in the literature. The structural vibration behaviour is closely linked to the flow characteristics. At T/d = 3:00, the cross-flow root-mean-square strain distribution shows a very prominent peak at the reduced velocity Ur ≈ 26 when the vortex shedding frequency fs, coincides with the third-mode natural frequency of the combined fluid–cylinder system. When T/d < 3:00, this peak is not evident and the vibration is suppressed because of the weakening strength of the vortices. The characteristics of the system modal damping ratios, including both structural and fluid damping, and natural frequencies are also investigated. It is found that both parameters depend on T/d. Furthermore, they vary slowly with Ur, except near resonance where a sharp variation occurs. The sharp variation in the natural frequencies of the combined system is dictated by the vortex shedding frequency, in contrast with the lock-in phenomenon, where the forced vibration of a structure modifies the vortex shedding frequency. This behaviour of the system natural frequencies persists even in the case of the single cylinder and does not seem to depend on the interference between cylinders. A linear analysis of an isolated cylinder in a cross-flow has been carried out. The linear model prediction is qualitatively consistent with the experimental observation of the system damping ratios and natural frequencies, thus providing valuable insight into the physics of fluid–structure interactions.

Vibration Excitation Force Measurements in a Rotated Triangular Tube Bundle Subjected to Two-Phase Cross Flow

2005 ◽  
Author(s):  
C. Zhang ◽  
M. J. Pettigrew ◽  
N. W. Mureithi
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Fretting Wear ◽  
Experimental Program ◽  
Force Measurements ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Drag Forces ◽  
Vibration Excitation ◽  
Excitation Force

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting-wear or fatigue. Detailed vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures over a broad range of void fraction and mass fluxes. Both the dynamic lift and drag forces were measured with strain gage instrumented cylinders. The experiments revealed somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions. The periodic forces appeared well correlated along the cylinder with the drag force somewhat better correlated than the lift forces. The periodic forces are also dependent on the position of the cylinder within the bundle.

scholarly journals Effect of Inclination on Vortex Shedding Frequency Behind a Bent Cylinder: An Experimental Study

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 100 ◽  
Author(s):  
Jorge Silva-Leon ◽  
Andrea Cioncolini
Keyword(s):  
Boundary Condition ◽  
Wind Tunnel ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Normal Incidence ◽  
End Effects ◽  
Present Design ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Flow Vortex

This paper presents experimental results on the vortex shedding frequency measured behind a bent cylinder. Experiments were conducted in a wind tunnel covering Reynolds numbers between 50 and 500, a range of interest for flow sensing, flow control, and energy harvesting applications. The bent cylinder comprised a vertical leg always oriented at normal incidence with respect to the free-stream flow, and an inclined leg whose inclination was varied during the tests between 90° and 15°. The bent cylinder was oriented in the wind tunnel with the vertical leg upstream and the inclined leg downstream, and the vortex shedding frequency was measured with hot-wire anemometry at several locations behind the inclined leg. The present bent cylinder design improves upon those previously considered by providing a finer control on the upstream boundary condition acting upon the inclined leg, which in the present design is not affected by the yaw angle of the inclined leg. With the exception of free-end effects, only noticeable for certain inclinations and Reynolds number values, inclination effects were surprisingly not observed, and the frequency of vortex shedding measured behind the inclined leg of the bent cylinder was consistent (within a few percent) with the cross-flow vortex shedding frequency at the same flow velocity. The present results corroborate and significantly extend the limited observations on bent cylinders available in the literature, further highlighting the importance of the upstream boundary condition on the vortex shedding process with inclined cylinders.

Two-Phase Cross-Flow Excitation of a Normal Square Tube Array: Experiments and Analysis

2002 ◽  
Author(s):  
Paul Feenstra ◽  
David S. Weaver ◽  
Tomomichi Nakamura
Keyword(s):  
Heat Exchanger ◽  
Vortex Shedding ◽  
Single Phase ◽  
Tube Bundle ◽  
Cross Flow ◽  
Scale Model ◽  
Phase Flow ◽  
Heat Exchanger Tube ◽  
Two Phase ◽  
Exchanger Tube

Laboratory experiments were conducted to determine the flow-induced vibration response and fluidelastic stability threshold of a model heat exchanger tube bundle subjected to a cross-flow of refrigerant 11 (R-11). The tube bundle consisted of a normal square array of 12 tubes with outer tube diameters of 7.11 mm and a pitch over diameter ratio of 1.485. The experiments were conducted in a flow loop that was capable of generating single-phase and two-phase cross-flows over a variety of mass fluxes and void fractions. The primary intent of the research was to improve our understanding of the flow-induced vibrations of heat exchanger tube arrays subjected to two-phase cross-flow. Of particular concern was the effect of array pattern geometry on fluidelastic instability. The experimental results are analysed and compared with existing data from the literature using various methods of parameter definition. Comparison of amplitude response in liquid flow with previous results shows a similar occurrence of symmetric vortex shedding that validates the scale model approach in single-phase flow. It was found that the introduction of a small amount of bubbles in the flow disrupted the vortex shedding and thereby caused a significant reduction in streamwise vibration amplitude. The fluidelastic stability thresholds for the present array agree well with results from previous studies. Furthermore, a good collapse of the stability data from various investigations is obtained when the fluid density is defined using the slip model of Feenstra et al. [1] and when an effective two-phase flow velocity is defined using the interfacial velocity model of Nakamura et al. [2].

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