bluuebunny/crossref_metadata_2025 huggingface dataset:
An Arbitrary Lagrangian–Eulerian Formulation of Two-Dimensional Viscoelastic Beams Based on the Consistent Corotational Method
Authors: Deng Lanfeng , Zhang Yahui , Chen Li-Qun
Published: March 2022

In this paper, an arbitrary Lagrangian–Eulerian (ALE) formulation based on the consistent corotational method is presented for the geometric nonlinear dynamic analysis of two-dimensional (2D) viscoelastic beams. In the ALE description, mesh nodes can be moved in some arbitrarily specified way, which is convenient for investigating problems with moving boundaries and loads. By introducing a corotational frame, the rigid-body motion of an element can be removed. Then, the pure deformation and the deformation rate of the element can be measured in the local frame. This method can avoid rigid-body motion damping. In addition, the elastic force vector, the inertia force vector, and the internal damping force vector are derived with the same shape functions to ensure the consistency and independence of the element. Therefore, different assumptions can be made to describe the local deformation of the element. In this paper, the interdependent interpolation element (IIE) and the Kelvin–Voigt model are introduced in the local frame to consider the shear deformation, rotary inertia, and viscoelasticity. Moreover, the presented method is capable of considering the arbitrary curved initial geometry of a beam. Numerical examples show that internal damping dampens only the pure elastic deformation of the beam but does not dampen the rigid-body motion. Three dynamic problems of a beam with a moving boundary or subjected to a moving load are investigated numerically by the presented formulation and the commercial software ansys to verify the validity, versatility, and computational efficiency of the presented formulation.
Equivalent Theodorsen Function for Fluidelastic Excitation in a Normal Triangular Array
Authors: Alyaldin Loay , Mureithi Njuki W.
Published: March 2022

Fluidelastic instability (FEI) remains the most important mechanism of flow-induced vibrations that can potentially cause large amplitude vibrations and early failure of nuclear steam generator tubes. In the present work, experimental tests are conducted to measure the unsteady and quasi-steady fluid forces acting on a normal triangular tube array of P/D=1.5 subjected to single-phase (water) cross-flow. The quasi-steady forces together with unsteady fluid forces are then used to estimate the time delay between the central tube motion and fluid forces on the tube itself. The time delay effect for the quasi-steady fluidelastic instability model is derived in the frequency domain in the form of an Equivalent Theodorsen Function. The results are compared to the first Equivalent Theodorsen function developed for rotated triangular array by Li and Mureithi [1]. Using the Equivalent Theodorsen Function, a stability analysis is carried out to predict the critical velocity for fluidelastic instability in a normal triangular array subjected to single-phase flow. The predicted stability threshold is consistent with previous published experimental data. The results show that the normal triangular array is more stable than the rotated triangular array.
Extravascular Cooling of Blood Using a Concentrated Thermoelectric Cooling Probe
Authors: Lee Connie Y. , Crouch A. Colleen , Jha Aman K. , Adapa Arjun R. , Diaz Jose A. , Pandey Aditya S. , Greve Joan M. , Pipe Kevin P.
Published: March 2022

Thermal therapies have strong potential for improving outcomes for patients suffering from cardiac arrest, neonatal hypoxic-ischemic encephalopathy, or medically refractory intracranial hypertension. We propose a novel tool to manipulate blood temperature through extravascular thermoelectric heat exchange of blood vessel walls and flowing blood. This tool is a concentrated cooling probe with several thermoelectric units combined to focus cooling at the application site. Using this tool, we aim to achieve desired levels of temperature control and potentially reduce complications associated with traditional intravascular or systemic thermal therapies. Leveraging the feedback control, speed, and reversible operation of thermoelectric cooling modules, the device can adapt to cool or heat as desired. Preclinical testing on rodent models confirmed rapid, significant reduction of intravenous jugular blood temperature when a prototype device was brought in contact with the left carotid artery (change in blood temperature of −4.74 ± 2.9 °C/h and −4.29 ± 1.64 °C/h for 0 °C and −5 °C cooling trials, respectively). Declines in rectal temperature were also noted, but at lesser magnitudes than for jugular blood (0 °C: −3.09 ± 1.29 °C/h; −5 °C: −2.04 ± 1.08 °C/h), indicating proof-of-concept of thermoelectric extravascular blood cooling within a relatively localized region of the body. With further improvements in the technique, there is potential for selective organ cooling via a reduction in the temperature of flowing blood.
The Effect of Multiple Coexisting Convective Modes in Determining Thermoacoustic Behavior of a Partially Premixed Swirl Flame
Authors: Sreedeep Sharan , Ramanan Vikram , Chakraborty Aritra , Chakravarthy Satyanarayanan R.
Published: March 2022

This study focuses on the effect of multiple heat release mode interactions on the amplitude of unsteady pressure oscillation for a partially premixed radial swirl burner, which uses methane as fuel. A range of operating conditions based on inlet airflow rate and global equivalence ratio is considered for this purpose. The pressure time series shows amplitude modulation at the dominant frequency for all the flow rates and equivalence ratios considered. Wavelet analysis based on continuous wavelet transform illustrates the presence of heat release rate fluctuations at multiple frequencies other than the dominant mode of pressure oscillation, with this more pronounced at low frequencies. Spectral proper orthogonal decomposition performed on time-resolved CH* chemiluminescence images reveal four dominant spatial modes of chemiluminescence, chosen based on the dominant wavelet coefficients for the same. The identified frequencies correspond to the duct-acoustic mode, helical mode (spectrally close to acoustic mode), low-frequency axisymmetric mode and low-frequency helical mode. The low-frequency helical mode (considered as the result of nonlinear interaction between acoustic and helical mode) and the low-frequency axisymmetric mode (considered to have independent existence) have similar spectral content. Amplitude modulation of unsteady pressure is found to be a result of the superposition of duct-acoustic mode and low-frequency axisymmetric mode, whereas reduction in overall pressure amplitude with the decrease in global equivalence ratio is seen to be a result of an increase in the dominance of low-frequency helical mode. The relative dominance of low-frequency helical mode over dominant pressure mode reduces the overall pressure amplitude.
Design for Life-Cycle Manufacture
Authors: Stoll Henry W.
Published: March 2022

As manufacturing companies become more comfortable with the design for manufacture (DFM) philosophy and more experienced in its practice, new opportunities for good design become possible. This paper presents a systematic, easy to use, methodology for applying the DFM philosophy at all stages of the engineering design process. Called design for life-cycle manufacture (DFLC), the approach focuses on three important considerations: (1) the physical concept, (2) the part decomposition, and (3) total product quality. The concept of total product quality is operationalized by decomposing it into three underlying components: quality of concept, quality of design, and quality of ownership. Each of these qualities is the focus of a particular step in the design for life-cycle manufacture methodology.
Shortening Production Cycle Times Through Setup Reductions and Quality Level Improvements
Authors: Diaby Moustapha
Published: March 2022

This paper addresses the issue of investing in reduced setup times and defect rates for a manufacturer of several products operating in a JIT environment. Demand for each product occurs at a constant rate. Production cycle times can be shortened by investing in setup time and defect rate reductions, respectively. The problem is to determine optimal levels of setup time reduction, defect rate reduction, and production cycle time for each product, subject to demand, process improvement budget, and manufacturing and warehousing capacity constraints, respectively. A general nonlinear optimization model of this problem is formulated. A convex geometric programming approximation of the model is developed in order to solve it. The approximation can be made to any desired degree of accuracy.
A Cost Model of New Electronic Products for Use During the Design and Development Phases
Authors: Shina Sammy G. , Saigal Anil
Published: March 2022

This paper outlines a methodology for developing a production cost model during the design phase of new electronic products. The model incorporates the analysis of the major steps required in the design and manufacturing process and the tradeoffs in specifying their capabilities. Several elements of traditional costing techniques such as activity based costing, capital equipment and manufacturing simulation are incorporated in this model. They are combined with quality measurement and improvement techniques such as the process capability index resulting in a comprehensive cost methodology that is sensitive to design quality, manufacturing yields and potential product volume.
Environmentally Conscious Design and Manufacturing: Concepts, Applications, and Perspectives
Authors: Zhang Hong C. , Kuo Tsai C.
Published: March 2022

Environmentally conscious design and manufacturing (ECD&M) is a view of manufacturing which includes the social and technological aspects of the design, synthesis, processing, and use of products in continuous or discrete manufacturing industries. The benefits of ECD&M include safer and cleaner factories, worker protection, reduced future costs for disposal, reduced environment and health risks, improved product quality at lower cost, better public image, and higher productivity. Environmentally conscious technologies and design practices will allow manufacturers to minimize waste and to turn waste into a profitable product. This paper updates information about ECD&M, which will in turn provide some general information, guidelines and references for research and implementation. In the meantime, more clear definitions of related terms used in the ECD&M area are provided. A brief future trend is also provided at the end of this paper.
Safety Analysis for a High Pressure Cylinder of an Oilfield Truck-Mounted Compressor
Authors: Zhou Si-Zhu , Chen Jacob Jen-Gwo
Published: March 2022

Regarding the safety analysis of a cylinder, the normal method is to consider it as a simplified thick-wall cylinder. According to the formulation of stress, safety about the thick-wall cylinder, the risk point and maximum stress, the deformation of a cylinder can be calculated. This method neglects the complex structure of the cylinder (the hole in it and the change of the cross-section area). However, it is necessary to do an accurate safety analysis for a high pressure, limited space cylinder mounted on a truck.

The objective of this paper is to present and illustrate a three dimensional finite element analysis for the safety of the high pressure cylinder and of the truck-mounted compressor. First, the model of finite element analysis is set up; then, the structure is divided into elements; after that, the risk cross-section and maximum stress of the cylinder are obtained. The stress curves about risk cross-section of the cylinder are drawn. Based on the results of the finite element analysis, the safety evaluation of the design is presented and the measurement about improving the safety coefficient of the cylinder are described.
Radiological Dose Estimates of Cassini Space Mission Accidents
Authors: Margulies T.
Published: March 2022

Calculations using three models support the need to prepare for radiological accidents that extend beyond ten miles from the launch area. Furthermore, re-entry events during gravity-assist orbits could exhibit environmental and health impacts from fall-out on countries that are not participating in this space endeavor.
Simulation of the Incompressible Viscous Cross-Flow Around an Oscillating Circular Cylinder via the Random Vortex Method
Authors: Akbari M. H. , Price S. J.
Published: March 2022

The random vortex method has been used to simulate the laminar incompressible flow around a circular cylinder oscillating transversely to the flow. The vorticity in the flow is represented by a number of discrete point vortices, which are given random walks to simulate the effect of viscous diffusion. The vortices are created on the cylinder surface to satisfy the no-slip boundary condition, they are convected using an inviscid flow assumption, where the induced velocities on each of the point vortices is obtained using a vortex-in-cell method. Using a time marching algorithim based on the above procedure, the flow around stationary and oscillating circular cylinders is investigated. In particular, the effect of frequency and magnitude of the forced oscillation on the dynamic force coefficients is considered. The results obtained are compared with other numerical solutions and with available experimental data. In general, both the qualitative and quantitative agreement between the present numerical simulation and other numerical results and experiments is good.
Vortex Structures in Flow Over a Rectangular Plate
Authors: Sheridan John , Hourigan Kerry , Mills Richard
Published: March 2022

Vortex shedding behind plates with rectangular trailing edges and both aerofoil and rectangular leading edges was investigated in a water tunnel. Previous studies, such as that presented by Mills et al. (1995), have shown that the base pressure, and hence drag, of such plates can be significantly altered by applying transverse perturbations at certain frequencies. Evidence has been presented to show that this is dependent on the interaction of shed vortices; this study is a first attempt to study the nature of the vortices and how they are influenced by the applied perturbation. This is done by using particle image velocimetry to measure the velocity field close to the plates. From these the vorticity field is derived and its response to perturbation examined. It is shown that the perturbation orders the vorticity field, resulting in increased peak vorticity and circulation in the shed vortices. Thus, their potential for inducing greater suction in the wake has been increased.
Vortex Induced Vibration of Chemical Plant Towers
Authors: Goyder H. G. D.
Published: March 2022

It is well known that vortex shedding can cause vibration of cylindrical structures. However, an actual case of vortex shedding from a chemical plant distillation column revealed that pipework on the outside of the column can cause the vibration to be significantly enhanced in comparison to that of a bare cylinder. This observation contradicts the commonly held view that equipment and pipework on the outside of cylinders reduces the effects of vortex shedding. Wind tunnel studies on a fully flexible sectional model of the column indicated that in some cases relatively small pipework can increase the vibration by a factor of three in comparison to the vibration of a plain cylinder. The case history, the wind tunnel studies and the solution adopted for the column are described in this paper.
Modeling Vortex-Excited Vibrations of Uniform Cylinders in Uniform and Shear Flow
Authors: Balasubramanian Sathish , Skop Richard A.
Published: March 2022

In recent years, nonlinear wake oscillator models have been shown to arise as a leading order approximation to the vortex shedding instability from a circular cylinder in a uniform flow (Alberéde and Monkewitz, 1992). Skop and Balasubramanian (1995) and Balasubramanian and Skop (1996) have extended the Van der Pol oscillator to model vortex shedding in non-uniform flow scenarios by introducing an axial diffusive coupling term in the equation. The results of their investigations have yielded a universal linear relationship between a turbulent kinematic viscosity that scales the diffusive coupling term and the shear parameter that quantifies the shear in the flow.

In this paper, following Skop and Balasubramanian (1997), we use the diffusively coupled Van der Pol oscillator as the governing equation for one component of the fluctuating lift force on the cylinder. The second component of the lift force is represented by a stall term which is linearly proportional to the transverse velocity of the cylinder. The coupled fluid-structural equations are employed to numerically simulate the response of a uniform pivoted cylinder in uniform and shear flow. The numerically predicted response amplitudes and bounds of lock-in are compared to available experimental results.
Failure Mechanism of a Thermocouple Well Caused by Flow-Induced Vibration: (1) — Numerical Simulation and Water Experiment of Flow-Induced Vibration
Authors: Yamaguchi Akira , Morishita Masaki , Wada Yusaku , Iwata Koji , Ichimiya Masakazu
Published: March 2022

In this paper, flow-induced vibration analysis and experiment of the thermocouple well sustained in cross flow of Japanese Fast Breeder Reactor Monju are performed. Navier-Stokes equations coupled with equations of structural motion are solved using the finite element method. The experiment is performed in water using real scale mock-up model. The in-line oscillation mode is simulated in both experiment and analysis and the results are consistent each other. Also observed in both the experiment and analysis are the symmetric vortices that are generated at both lateral sides of the cylinder in accordance with the cylinder natural frequency. Furthermore, it has been found both in numerical simulation and experiment that the thermocouple well oscillates at decreased flow rate if the natural frequency of the thermocouple is reduced. Based on the analytical and experimental results, a displacement response diagram that relates the displacement and the reduced velocity is established.
Failure Mechanism of a Thermocouple Well Caused by Flow-Induced Vibration: (2) — Interaction Between Flow-Induced Vibration and Fatigue Crack Growth in a Thermocouple Well
Authors: Wada Yusaku , Morishita Masaki , Yamaguchi Akira , Iwata Koji , Ichimiya Masakazu
Published: March 2022

In the preceding paper a simplified master diagram on the relationship between a reduced velocity Vr (= V/fD) and a reduced displacement amplitude y/D is investigated for the in-line oscillation mode of thermocouple well. Based on this diagram, high cycle fatigue failure process of a thermo-couple well; crack initiation, crack growth/arrest, and final stage of fracture, is evaluated in this paper.

The strain amplitude at the root between thin and thick well tubes can be analytically estimated considering the sharp notch effect, and the crack initiation life can be evaluated using a fatigue curve. After short crack growth the crack front line can move as a long crack. Both of natural frequency and damping constant are changed, and crack growth reduces the displacement amplitude. As the results crack arrest and delayed failure, which are peculiar in flow-induced vibration, can occur in a thermometer.
The Applicability of the Quasi-Steady Assumption for Two Staggered Circular Cylinders in Cross-Flow
Authors: Ting D. S.-K. , Wang D. J. , Price S. J. , Païdoussis M. P.
Published: March 2022

The applicability of the quasi-steady assumption for two staggered circular cylinders of equal diameter in cross-flow has been tested for ten geometrical arrangements, for Reynolds number (based on cylinder diameter and free-stream velocity) 4 × 104 ≤ Re ≤ 2 × 105, and reduced flow velocity 15 ≤ U/fD ≤ 300. With one cylinder stationary, the other one is forced to oscillate transversely to the flow with a half peak-to-peak amplitude / cylinder diameter ratio of 0.043, 0.047 or 0.17. The dynamic forces are deduced either from measured pressure distributions, or from direct force measurements on the cylinder, and these measurements are post-processed in the time and frequency domains, respectively. The applicability of the quasi-steady assumption is found to be strongly dependent on the relative positions of the two cylinders, in addition to U/fD. When the cylinder is in a sensitive flow region, where the spatial gradients of the static force coefficients are high, the quasi-steady assumption may not be applicable even for U/fD = 250. Away from the sensitive flow regions, the quasi-steady assumption is usually applicable for U/fD ≥ 50. In general, the fluidelastic forces depart rapidly from predictions based on the quasi-steady assumption with decreasing U/fD below the critical value.
Experiments on Vortex-Induced Vibrations of Pivoted Circular Cylinders
Authors: Szewczyk Albin A. , Balasubramanian Sathish , Haan Fred L. , Skop Richard A.
Published: March 2022

An experimental study of the vortex-induced vibrations of a pivoted circular cylinder was conducted to investigate the regions of lock-in between the vortex shedding and body vibration frequency for uniform and shear flow in Reynolds number ranges from 16,500 to 22,000. A rigid circular cylinder pivoted at the top by a bearing and stiffened by two transverse springs at the bottom was mounted in a wind tunnel. The cylinder was allowed to oscillate only in the cross-flow direction. The lock-in region was approached by varying the flow velocity. Measurements were made of the width of the frequency lock-in range, response amplitude, displacement time series and power spectral densities of the wake shedding for different Re numbers.
Vortex Shedding From a Rotary Oscillating Cylinder
Authors: Fujisawa N. , Ikemoto K. , Nagaya K.
Published: March 2022

Vortex shedding resonance of a circular cylinder wake to a forced rotational oscillation has been investigated experimentally by measuring the velocity fluctuations in the wake, pressure distributions over the cylinder surface, and visualizing the flow field with respect to cylinder oscillations. The vortex shedding resonance occurs near the natural shedding frequency at small-amplitude of cylinder oscillations, while the peak resonance frequency shifts to a lower one with an increase in oscillation amplitude. The estimated drag and lift forces acting on the cylinder indicate that the phase lag of fluid forces to the cylinder oscillations increases with an increase in oscillation amplitude, supporting the change of resonance frequency with oscillation amplitude. The comparative study of the measured pressure distributions and the simultaneous flow visualizations with respect to cylinder rotation shows the mechanisms of phase lag, which is due to the strengthened vortex formation and the modification of the surface pressure distributions.
Simulation of the Behavior of a Catamaran in Large Amplitude Motions
Authors: Tessier J. B. , Peseux B. , Delhommeau G.
Published: March 2022

A numerical model has been developed to study the large-amplitude motions of a catamaran subjected to severe wave conditions. In this paper, emphasis is placed on the description of the theoretical aspects. The nonlinear equations of motion concerning the rigid hulls and flexible beams are developed, including large rotations between bodies. The fluid-structure interaction model satisfies exactly the body boundary condition on the instantaneous surface of the moving body, defined as the part under the incident wave profile, while the free surface boundary conditions are linearized. The problem is solved using a transient free-surface Green function singularity distribution method.

The simulation of a nonlinear global behavior of a catamaran in following waves has been obtained and it illustrates the importance of nonlinear effects associated with the changing wetted hull.
A Low-Dimensional Model for Vortex Shedding Patterns Behind Vibrating Flexible Cables
Authors: Olinger D. J.
Published: March 2022

A recent focus in studies of vortex shedding behind circular cylinders has been the use of low-dimensional dynamical systems to predict wake dynamics. Use of purely temporal models has been limited by their inability to describe three-dimensional spatial flow variations along the cylinder span; a hallmark of transitional flows such as the cylinder wake. In the present work this limitation is overcome by developing a spatial-temporal map lattice utilizing a series of coupled circle map oscillators along the cylinder span. This model allows for study of vortex shedding patterns and wake dynamics behind vibrating flexible cables with prescribed frequency, amplitude, and mode shape. Standing wave mode shapes and traveling waves along the cable span are modeled. Lace-like vortex patterns are observed for the standing wave case. For traveling waves oblique shedding patterns are confirmed. Non-harmonic forcing outside the classical lock-on region yields vortex dislocation patterns in the wake.
The Singular Nature of Rotating Circular Rings With Symmetry
Authors: Quinn D. Dane , Clemons Curtis B. , Dempsey Kevin M.
Published: March 2022

We study the S𝒪(2) symmetric deformation of circular rings. The equations of motion are based on general partial differential equations governing the elastodynamics of geometrically exact rings, which have been formulated by Dempsey [2], based on the work of Libai and Simmonds [6]. Thus, the formulation is valid for arbitrary pressure forcing, large deformations, and finite strains, although the results are tempered by a linear constitutive relation and an assumption of plane strain.

With the assumption that the deformation retains S𝒪(2) symmetry, the partial differential equations are reduced to a set of coupled ordinary differential equations. Within this restricted space of solutions, we study the existence and stability of relative equilibria and discuss the effects of constant hydrostatic pressure on the dynamical response. Specifically, we find that interaction between inertial effects arising from rotational motion and the combined elastic and external pressure forces can produce unexpected behavior, including the existence of a “buckled” state which retains the symmetry, yet physically implies that material planes do not lie in the radial direction. Such a state is shown to effect the large-amplitude response of the system in a singular limit of the governing equations.
Dynamic Response of a Rod due to Vortex-Induced Vibration
Authors: Massih A. R. , Forsberg K.
Published: March 2022

The dynamic response of a circular cylinder subject to cross-flows is analyzed using the wake oscillator model of Iwan and Blevins. The nonlinear differential equations for the system is solved by an approximate algebraic method and the results are compared against full numerical solutions with excellent concordance. Also we have compared the predictions of tube displacements and vortex frequencies with available experimental data. Finally, the computational fluid dynamics code ADINA-F and the structural mechanics code ADINA are used concurrently to study the dynamic behavior of the system.
Aerodynamic Noise Calculation of a Detaching Flow
Authors: Huang S. , Béguier C.
Published: March 2022

A numerical study based on the macro-simulation method is carried out in order to determine the aerodynamical noise of a turbulent detaching flow. The macro-simulation method uses a Large Eddy Simulation (LES) code to obtain at the same time, the large structures of the flow and the small structures modelled by a sub-grid eddy viscosity, and an acoustic code able to calculate, in the far field, the radiated aerodynamical noises, from the Lighthill-Curle formalism. The method permits to dissociate the different aerodynamical noises: the wall noise, due to the wall-pressure fluctuations, the shear noise, due to the large scale quadrupole sources, and the turbulence self noise, generated by the small scale quadrupole sources. The case of the normal backward facing step is presented, for which the different emitted noises are analysed and compared together. Some theoretical hypotheses are also tested.
Wall-Pressure Fluctuations Under a Three-Dimensional Boundary Layer
Authors: Panton Ronald L.
Published: March 2022

This paper gives a simple model of the pressure spectrum in wavenumber-phase velocity space for three-dimensional boundary layers. Equally as important is the definition proposed for a vector convection velocity and the method proposed for conversion of wavenumber-frequency variables into wavenumber-phase velocity variables. In three-dimensional flows one must define a phase speed that is a vector c = (c1, C3). A complete vector wave speed cannot be determined from pressure data, however, the component ck in the direction of k, ck ≡ Ω/k, can be defined and is found to be sufficient. Here k is the wave vector magnitude and α its direction. This allows the spectrum function to be well represented in the polar form Φ(k, α, ck). Moreover, for given k, a convection velocity may be defined as the point of maximum Φ(k, α, ck). Convection velocity is expressed in the form of a magnitude ck_max(k) and direction αmax(k). The three-dimensional spectrum model was produced as a generalization of Witting’s two-dimensional model. By splitting the boundary layer into two parts, the simplest generalization is formulated. Each part has its own transport velocity vector. Sample calculations are displayed as contour plots of Φ (ck, α) for fixed wavenumber k. On such plots the maximum is the convection velocity. The plots reveal an abrupt transition in the spectrum as the wavenumber increases; a result of the two layer assumption.
The Flow Dynamics of an Asymmetrical Circular Cylinder Under Acoustic Excitation
Authors: Lo K. W. , Ko N. W. M.
Published: March 2022

In the present study, the asymmetry of the cylinder was achieved by attaching a 90° V-grooved strip on the cylinder surface. Different flow regimes are present on the grooved and smooth halves. Under acoustic excitation, the flow regimes over the two halves are changed and the near wake structures of the grooved cylinder are modified. Further, the transition process is not stationary in time and two different transient processes are observed during the transition.
Stability of a Horizontally Rotating Fluid-Tube Cantilever
Authors: Panussis Dimitrios A. , Dimarogonas Andrew D.
Published: March 2022

The case of simultaneous in-plane and out-of-plane lateral vibrations of small amplitude of a horizontally rotating cantilever tube conveying fluid is examined. The rotation is with respect to the fixed end of the tube at a constant angular velocity. The diameter of the tube is constant and much smaller than its length. There is no nozzle attached at the free end. The tube is inextensible. Two inter-dependent partial differential equations in the two directions of deflection of the system are derived by means of the equilibrium of forces on a fluid-tube element. The same system of equations is derived by means of Hamilton’s principle. An approximate solution is sought in the case of linearized out-of-plane lateral vibrations in the form of a series of normalized eigenfunctions from the linear cantilever beam theory using Galerkin’s method. The threshold of instability, namely the critical dimensionless circular frequency and speed of flow at the onset of instability of the fluid-tube cantilever are investigated. The numerical results show that the externally applied constant rotational speed increases the critical circular frequency and speed of flow compared to the non-rotating fluid-tube cantilever, thus, increasing the stiffness of the system.
Theoretical Instability Analysis of a Rotating Flexible Disk Subjected to Swirling Fluid Flow
Authors: Watanabe Masahiro , Hara Fumio
Published: March 2022

This paper deals with a theoretical instability analysis of a rotating flexible disk subjected to swirling fluid flow, resulting in the generation of a strong coupling between the flexible disk vibration and swirling fluid flow around it, and a possible mechanism governing unstable vibration. In the instability analysis, the basic equations of swirling fluid flow around the rotating disk are based on Navier-Stokes equations integrated over the gap width between the rotating disk surface and the shroud wall. The structural vibration equation of the rotating flexible disk is based on the Kirchhoff-Love plate model. The equations of coupled fluid-structure motion take into account the moving boundary conditions with respect to both the rotating disk and the fluid flow. These equations are linearized for small deflection of the disk near the equilibrium state, and the solution of these equations is obtained using the multimodal expansion approximation and applying the Galerkin method. The theoretical results show a good agreement to the experiment with respect to the unstable vibration mode shapes and dependence of the instability frequency on the rotating speed, but only a qualitative agreement for the critical speed at which the disk’s unstable vibration occurs.
A Friction-Based Model for Fluidelastic Forces Induced by Axial Flow
Authors: Porcher G. , de Langre E.
Published: March 2022

Self excitations of slender structures under axial flow have been reported in a large variety of local flow configurations. This paper reports on the analytical results of a research program aimed at studying basic phenomena leading to fluidelastic instabilities.

A friction-based model is proposed to calculate the fluidelastic forces induced by axial flow. It is developed here for an axial flow between two surfaces. This method is an extension of the studies which were carried out by Miller (1970), Hobson (1982) and Mulcahy (1988). A pressure drop is introduced in the system with a local or continuous pressure drop factor. This model is based on a modal analysis and is presented for structures with several degrees-of-freedom.

The continuity and momentum equations are integrated along the fluid domain thickness with the boundary conditions on the structure. A linearization of these equations gives the expression of the fluctuating velocity and pressure. With a modal analysis, the fluidelastic force expression is obtained by the integration of the pressure on the structure wall. Three terms, called added terms, are identified: inertial, damping and stiffness. For several cases and different locations of the pressure drop, the behavior of this system and the flutter instability are analysed.
Hydroelastic Vibration of Free-Edge Annular Plates
Authors: Kwak Moon K. , Amabili Marco
Published: March 2022

This paper is concerned with the virtual mass effect due to the presence of water on the natural frequencies of free-edge annular plates resting on free surface, which has never been studied theoretically. Recently, experiments were carried out for free-edge annular plates to find the so-called non-dimensionalized added virtual mass incremental factors. In this paper, theoretical non-dimensional added virtual mass incremental factors are obtained by employing the Hankel transformation technique in conjunction with the Fourier-Bessel series approach. It is found that the theoretical non-dimensionalized added virtual mass incremental factors for free-edge annular plates resting on free-surface agree well with experimental ones.
Fluid-Damping-Controlled Instability of Tubes in Crossflow
Authors: Chen S. S. , Cai Y. , Srikantiah G. S.
Published: March 2022

Motion-dependent fluid forces are measured in a water channel. From the measured fluid forces, fluid-stiffness and fluid-damping coefficients are calculated as a function of reduced flow velocity, oscillation amplitude, and Reynolds number. Once these coefficients are known, the mathematical model based on the unsteady-flow theory can be applied to predict structural instability due to fluid damping. The cases we considered are a single tube, twin tubes, tube row, triangular array, and square arrays. The results show instability regions that are based on the fluid-damping coefficients and provide answers to a series of questions on fluidelastic instability of tube arrays in crossflow.
A Fluidelastic Instability Model With an Extension to Full Flexible Multi-Span Tube Arrays
Authors: Li Ming , Weaver David S.
Published: March 2022

An analytical model was developed for the prediction of fluidelastic instability in cross flow multi-span heat exchanger tube arrays. The model is based on concepts developed by Lever and Weaver, as well as Yetisir and Weaver, but is modified and extended to include other important factors. Rather than the nonlinear function previously used, a linear area perturbation decay function is introduced to account for the decay of disturbances away from an oscillating tube. Thus, an analytical solution can be obtained. Flexible tubes directly two rows upstream and downstream of a central tube, neglected in the earlier work, are included in the present model. Improved agreement with experimental data is obtained for parallel triangular tube arrays. In contrast, little improvement is achieved for the other tube patterns due to the reduced influence of the upstream tube wake. The velocity distribution and mode shape along the tube span are also introduced into the model. This is made possible because of the explicit stability equation. Therefore, the present model can be used to calculate the fluidelastic instability for the multi-span tube arrays. Comparison between theory and experimental data shows good agreement.
Experimental and Computational Investigation Into Vibration Wear of Control Rods in French PWRs
Authors: Borsoi Laurent , Canteneur Christian , Barbe Gérard
Published: March 2022

The under-card wear of control rods due to flow-induced vibration was discovered in 1986. To cope with this phenomenon, Framatome at once erected the full-scale Magaly test facility, in operation since 1988. Then in 1991 Framatome initiated exploratory numerical simulations using the Nat03 structural code specifically developed for this purpose. After introducing Magaly and Nat03, this paper illustrates how the following ill-posed inverse-problem has been attacked: from rod vibration measured with Magaly, how to calibrate via Nat03 computation a rustic model of the rod excitation created by the main flow coming from the fuel assembly. A single force applied on the control rod just beyond the continuous guidance section is sufficient to “support” after adjustment all the available experiment-computation comparisons: rod displacement (trajectory, standard deviation, PSD), contact force (average value, contact duration), and wear work rate, for three control rods differently located in the cards and nine card elevations with different flow rates.
Prediction of Tube Wear due to Flow-Induced Vibration in PWR Steam Generators
Authors: Rao M. S. M. , Laskowski L. J. , Srikantiah G. S. , Ahluwalia K. S.
Published: March 2022

Tube wear due to flow-induced vibration has been of continuing concern in operating Pressurized Water Reactor steam generators. Tube plugging or repair is necessary when inservice inspection indicates tube wall thickness less than a minimum acceptable value. Additional considerations involve the use of tube stabilizers or motion limiters when a plugged vibrating tube can impact on its neighboring active tubes. An analytical wear assessment methodology that predicts tube wear caused by flow-induced vibration is described. The methodology is based on determining a set of wear parameters from a non-linear finite element simulation of the steam generator tubes incorporating clearances at the tube supports under flow-induced turbulence and fluidelastic excitation. Tube wear progression during steam generator life is projected from the analytically determined parameters and experimental wear correlations. The methodology is applied to predict tube wear at scheduled inspections in a steam generator.
Improved Estimation of Fluidelastic Instability Threshold for Tube Arrays in Two-Phase Flow: A Model Incorporating Temporal Fluid Force Correlation Along the Tube Axis
Authors: Nakamura T. , Chen S. S. , Mureithi N. W. , Kusakabe T.
Published: March 2022

The unsteady flow model for the prediction of fluidelastic instability in tube arrays has been employed successfully to single phase cross-flow. Stability boundaries as well as inter-tube vibration mode patterns can be predicted.

Single phase flow studies are a precursor to the ultimate practical problem of fluidelastic instability in heat exchangers where the flow consists of two co-existing phases. In principle, existing unsteady fluid force models can be applied to two-phase flow induced vibration. However, the models become intractably complex for the case of U-bend tubes in two-phase flow. In single phase flow, the fluid forces may be considered to be fully correlated along the tube span. This is not the case for two-phase flow. For tube lengths much longer than the typical linear dimension of the two phase flow unit structure (slug, bubble etc.), forces along the tube span are only partially correlated.

In this paper, an unsteady flow model taking into account partial spanwise correlation is presented. The model is applied to fluidelastic analysis of a long span heat exchanger tube. Preliminary results show that the effect of partial correlation is to reduce the effective net fluid forces which thus raises the effective instability threshold. Another important result is the introduction of additional coupling between modes that would otherwise be uncoupled in the fully correlated case. This has important implications for heat exchanger tubes which have closely spaced modes.
Damping of Heat Exchanger Tubes in Two-Phase Flow
Authors: Pettigrew Michel J. , Taylor Colette E.
Published: March 2022

Two-phase flow exists in many shell-and-tube heat exchangers such as condensers, evaporators and nuclear steam generators. Some knowledge on tube damping mechanisms is required to avoid flow-induced vibration problems.

This paper outlines the development of a semi-empirical model to formulate damping of heat exchanger tube bundles in two-phase cross-flow. The formulation is based on information available in the literature and on the results of recently completed experiments. The effects of several parameters such as flow velocity, void fraction, confinement, flow regime and fluid properties are discussed. These parameters are taken into consideration in the formulation of a practical design guideline.
Modelling of the Seal Flow Between an Impeller Shroud and the Static Housing With an ALE Method: Comparison Between Calculated and Measured Dynamic Coefficients
Authors: Undreiner S. , Frei A.
Published: March 2022

The leakage flow between the shroud-pump impeller and its housing is simulated with a Navier-Stokes solver. The fluid-structure interactions are modelled with an Arbitrary Lagrangian Eulerian method (ALE). The force components and the rotordynamic coefficients obtained from the numerical simulation are compared to those calculated from measurement. The Navier-Stokes solver is a finite element code, N3S, developed by “Electricité de France”. It solves the Reynolds-averaged Navier-Stokes equations, with a standard k-ε model. The ALE method consists in a calculation of a mesh velocity. A first order approximation provides equations similar to the standard Navier-Stokes equations. Sulzer-pumps has performed measurements. The test installation consists of a test rig, a closed loop with the required components for pressure, temperature, and flow control, and a data acquisition and handling system. This test rig allows the identification of the rotordynamic coefficients of pump rotor components like impeller and annular seals. The dynamic coefficients comparison shows a good prediction of the numerical model, except for the stiffness coefficients. Other functionning conditions have to be tested before to conclude on the ALE model abilities. Although the requiered CPU time to reach the convergence is long, this type of model can be very interesting in the future for such a complicated 3D flow.
Transverse Vibrations of Fluid Filled Bellows Expansion Joints
Authors: Jakubauskas V. , Weaver D. S.
Published: March 2022

A theoretical model is developed for the transverse vibrations of bellows expansion joints. The model is based on Timoshenko beam theory and includes the added mass effect of an internal fluid. An analytical expression for bellows natural frequencies is developed in the form of a Rayleigh quotient and is presented in a way which is suitable for hand calculations. The results for the first four transverse modes are compared with experiments as well as the predictions of the simplified analysis of the Expansion Joint Manufacturers Association (EJMA). While the present analysis agrees well with experiments, the EJMA approach can be substantially in error due to its neglect of rotary inertia and the convolution distortion component of fluid added mass.
An Investigation of Flow-Induced Multiple-Mode Vibrations of Gates
Authors: Billeter Peter , Staubli Thomas , Volkart Peter
Published: March 2022

An experimental investigation of flow-induced vibrations of gates with multiple degrees-of-freedom will be presented: An underflown vertical gate plate was allowed to oscillate both in the cross-flow (z-) and in the streamwise (x-) direction. The two purposes of the investigation were to further the insight into the hydrodynamic coupling mechanisms of the two vibration modes and to determine the interaction of the unsteady lift and drag forces. Self-excited vibration tests were run with reduced velocities Vrz and Vrx from 0.8 to 14 covering a range in which the instability-induced excitation (IIE) due to impinging-leading-edge-vortices (ILEV) as well as the transition to galloping (MIE) occurred. The ratio of the natural frequencies of the two vibration modes fx0/fz0, the gate opening ratio s/d, and the submergence of the gate plate were varied. Depending on the ranges of reduced velocities and frequency ratios, a complex interaction of two different kind of instability induced excitation was detected. Furthermore, it was found that streamwise IIE-excitation and cross-flow galloping coexist simultaneously. To assess the relevant fluid dynamic amplification and attenuation mechanisms, simultaneous body response and flow velocity measurements were carried out.
Systems Analysis of Launch Vehicle Aeroelastic Coupling
Authors: Dotson K. W. , Baker R. L. , Bywater R. J.
Published: March 2022

Forces due to alternating flow states on the payload fairing of launch vehicles can couple with structural responses during transonic flight. A new methodology for the assessment of this type of self-sustained oscillation is applied for an actual launch vehicle mission. Corresponding internal launch vehicle loads are compared with those for the other transonic airloads events. The limit cycle amplitude from the analysis is compared with that from application of an existing technique in the literature. It is shown that the new methodology can be significantly less conservative than the stability criterion for bounded system responses. The historical assumption that the alternating flow forces on the payload fairing couple with a single launch vehicle bending mode is investigated through transient analysis of the fully coupled system. Evidence of alternating flow separation in flight data for the Titan IV launch vehicle is presented.