bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Inverse Method for the Identification of a Distributed Random Excitation Acting on a Vibrating Structure: Part 2 — Flow-Induced Vibration Application
Authors: Perotin L. , Granger S. 
Published: March 2022

Abstract
In order to improve the prediction of wear problems due to flow-induced vibration in PWR components, an inverse method for identifying a distributed random excitation acting on a dynamic system has been developed at EDF. This method, whose applications go far beyond the flow-induced vibration field, has been implemented into the Meidee software.
A theoretical presentation of this method is proposed in the first part of the paper. The second part illustrates an application of this inverse excitation identification process on a flow-induced vibration experiment. The experimental set-up consists of a straight tube submitted to a complex three-dimensional turbulent water flow. This tube, clamped at one end, can be supported in various ways at the other end. The structural response measured in a linear support configuration taken as a reference is first used to identify the turbulent excitation exerted on the tube. The experimental results obtained with other supports are then used to validate the identified turbulent excitation and, thus, the inverse estimation process presented in the first part of the paper.
Simple Vortex Models for Vibration and Noise Caused by a Flow Over Louvers in a Cavity Opening
Authors: Looijmans K. N. H. , Bruggeman J. C. 
Published: March 2022

Abstract
Sound generation by a grazing flow over a cavity without and with a grid of louvers in the opening is investigated. Simple vortex models are presented that describe the hydrodynamic resonance condition of self-sustained flow oscillations for rigid and elastic louvers. Calculations show that in both cases resonance can occur in distinct intervals of the Strouhal number based on the louver distance. The sound power radiated by elastic louvers is analysed. It is shown that flow-induced vibration of the louvers can be eliminated by increasing louver thickness.
Analytical Model for the Periodic Pressure Fluctuations Induced by Flow Over a Cavity
Authors: Kook Hyungseok , Mongeau Luc 
Published: March 2022

Abstract
The interior of an open cavity exposed to a grazing flow is known to experience strong periodic pressure oscillations sustained for a wide range of flow velocities. In this study, an analytical model was investigated to allow predictions of the amplitude and the frequency of the pressure fluctuations induced inside the cavity. The flow-excited cavity system was assumed to be described in the frequency domain by two gain functions, forming a limit cycling closed-loop. The forward gain function is associated with the excitation mechanism, governed by the shedding of discrete vortices within the shear layer over the orifice. The backward gain function is associated with the acoustic response of the cavity resonator. An original approach was followed to determine the forward gain function, based on the vorticity formulation of the equations of motion (the so-called “vortex sound” theory). The analytical model was experimentally verified for a range of flow velocities and orifice dimensions. The predictions were found to be in good agreement with experimental observation.
Characterization of the Wind Noise Loading of Production Automobile Greenhouse Surfaces
Authors: Coney W. B. , Her J. Y. , Moore J. A. 
Published: March 2022

Abstract
Flow noise reaches the automobile interior through a variety of mechanisms including the aerodynamic excitation of vibration and its reradiation from greenhouse surfaces (the roof and glass panels). This paper describes an experimental characterization of this wind noise loading and an approximate procedure for its prediction.
Experimental procedures and unique instrumentation to measure parameters characterizing wavenumber-frequency spectra of the wind noise loading, i.e. wall pressure fluctuations, during wind tunnel tests of unmodified production automobiles are described. Results in the form of localized Corcos model parameters are presented.
The present modeling approach is semi-empirical, utilizing normalized wall pressure spectra. Steady flow data are used to scale the normalized spectra and to identify regions of differing flow structure which have each been assigned characteristic spectra. Spatial variation in predicted pseudo-noise is compared with measured values for several test configurations.
Method for Measuring the Sound Intensity of Rotating Broadband Aerodynamic Noise Sources
Authors: Haid Daniel A. , Mongeau Luc 
Published: March 2022

Abstract
A method was investigated for the measurement of the near field sound intensity of rotating broadband noise sources. The method used two sound intensity probes held stationary in the laboratory reference frame, which were conditionally sampled to track the motion of pre-defined rotating source regions along their circumferential path. The cross-correlation coefficient of the sound intensity for a single location in the rotating frame of reference was then calculated from the two stationary probe signals. Multiple probe spacings provided the information required for an estimate of the cross-correlation function, which was then Fourier transformed to yield the sound intensity spectrum. The method was validated using known stationary random signals, and the numerical simulation of a rotating source. The source spectrum in each case was successfully estimated despite leakage, a high variance, and a bias error in the intensity. The method was then applied to a mixed flow automotive cooling fan and the results were compared to flow measurements.
Aerodynamic Characteristics of Pressure-Pad Air Bars
Authors: Chang Y. B. , Moretti P. M. 
Published: March 2022

Abstract
Air flotation ovens are widely used for non-contact support and drying of coated papers and plastic films (generically called webs). The main components in air flotation ovens are air bars which have slot nozzles through which hot air jets are ejected. Problems in air flotation drying techniques include sideward motion of the web, web flutter, and contact between the web and air bars. The key to analyzing these problems is to determine the aerodynamic forces on the web. This paper discusses the aerodynamic forces generated by pressure-pad type air bars, each of which has two slot nozzles. Ground-effect theories, which were originally developed for the design of hovercraft, are applied to air bars. Aerodynamic forces for typical air bars were measured for different values of flotation height, and the results were compared with the theories. It is shown that ground effect theories can be applied to pressure-pad type air bars if we properly define the equivalent values of the ground effect variables, which include nozzle thickness (thickness of air jet), flotation height, angle of ejection of air jet, and total pressure of the air jet at the nozzle.
A Study on the Mechanism of Turbulence Generation in an Elbow
Authors: Yokouchi J. , Hagiwara T. , Saito N. , Takigawa Y. 
Published: March 2022

Abstract
We have experimentally investigated turbulent flow in an elbow in order to establish a model for the vibrations excited by turbulence. Velocities were measured in a piping system with an elbow. The test section consisted of straight pipes with a single 90° elbow.
Measurements of flow velocity distribution and intensity of turbulence were carried out in the region Re = 1 × 105 ∼ 3 × 105. The measurements were performed in cross sections 1D ∼ 4D down an exit of an elbow by laser Doppler velocimetry. Each cross section had 37 measurement points.
We compared the axial velocity distribution with the turbulence intensity. The larger the turbulence intensity was, the higher the mean velocity was. Also the turbulence intensity was related to the spatial gradient of the mean velocity. Both the effects of mean velocity and its spatial gradient were dominant in the mechanism of turbulence production.
As a result of this study, the authors compiled a database on the turbulence excitation source of an elbow pipe and obtained a hypothesis on the relationship between mean velocity distribution and vibration sources. Both the database and the hypothesis are presented in this paper.
Non Linear Vibrations of Loosely Supported Tubes Excited by Fluidelastic and Turbulence Forces
Authors: Hadj-Sadok C. , Payen T. , de Langre E. 
Published: March 2022

Abstract
For predictive analysis of flow-induced vibration and wear of heat exchanger tubes, non linear computation of tube dynamics may be performed using adequate modelisation of the fluid forces. This paper presents computations of the response of loosely supported tube to fluidelastic forces and turbulence. Computations are performed using the time-domain dynamic equations, which are projected on the modal basis of the tube (Axisa et al, 1988, de Langre et al, 1992). The fluidelastic forces are modeled as reduced velocity dependent fluid-stiffness and fluid-damping coefficients obtained with the Price and Païdoussis model. Random turbulence forces are estimated as function of flow rate from the experimentally measured power spectral density function (Axisa et al, 1990). A corrective methodology is proposed to account for the frequency dependence associated with fluid-stiffness and fluid-damping coefficients. Good agreement is obtained with computations using direct time dependent fluidelastic forces of the model.
New Design Recommendations for Fluidelastic Instability in Heat Exchanger Tube Bundles
Authors: Schröder Kai , Gelbe Horst 
Published: March 2022

Abstract
The “VDI-Wärmeatlas”, the standard design handbook for heat exchange in Germany, now includes a new guidline for vibration excitation in heat exchanger tube bundles (Gelbe et al. (1997)). Chapter 3 deals with the fluidelastic instability, which is the most important excitation mechanism to be considered when disigning tube bundle heat exchanger. The existing recommendations from Chen (1987), Weaver and Fitzpatrick (1987) and Pettigrew and Taylor (1991) differ in the suggested equations to calculate critical velocities for single phase cross-flow. With an extensive evaluation and test of consistency of these and new available data on this topic, new correlations are derived. Uniform definitions of critical flow velocity for instability, damping, natural frequency and hydrodynamic mass are used; their values are to be determined in still fluid with the density ρ. Confident documented data show only a small scatter. The other data deviate more, but mainly to the safe side.
The stability constant is a function of the tube pitch ratio for all tube bundle configurations subjected to liquid or gas cross flow, except for the rotated triangular one. The pitch ratio has the strongest influence for the normal triangular array and the influence becomes less for the rotated as well as the in-line square configuration. This significant influence of the pitch ratio and the tube bundle configuration on the stability constant enables a reasonable interpolation for non-standard configurations. The exponent of the dimensionless mass-damping parameter for gas cross flow depends on the standard tube configuration and is 0,5 for the 30°- and 45°- and 0,45 for the 60°- and 90°-configurations. For liquid flow a uniform exponent of 0,15 has been observed.
An Empirical Wear Projection Technology With Steam Generator Tube Applications and Relations to Work-Rate and Wear Simulations / Tests
Authors: Frick Thomas M. 
Published: March 2022

Abstract
This paper introduces an empirical Wear Projection Technology (WPT) which relies solely on data from two (or more) time-independent wear related measurements at a wear site. The development and application of this WPT insures that it is completely general in nature. Thus, WPT is potentially useful for all wear experiences where measurements and related extrapolations and interpolations can be made before a “failure” occurs.
When applied to nuclear plant steam generator tubes using non-destructive examination measurements (obtained during in-service inspections) as input, WPT enables mechanism (typically turbulence and / or fluid-elastic induced vibration) independent and motion-type (sliding-only, impact-sliding or impacting) independent projections for each site with an ongoing wear process. A single application, or successive applications in a monitoring mode, provides the basis for proactive planning of inspections as well as for required decisions regarding the short and long term maintenance of that specific tube, of that specific steam generator, and finally, of that entire plant. Appropriate timing and number of applications provides plant operators with the basis to assure safe (and commercially optimum) continued operation under either constant or changing operating conditions.
This paper presents the development of WPT along with example results from steam generator tube straight-leg and U-bend applications. These applications include an input data error assessment and a qualification. Views on how WPT relates to the Proposed US-NRC Steam Generator Rule for the tube wear degradation mode, and how it can be used to implement an Alternate Plugging Criteria, are provided. Ideas relative to the implementation of the original wear process model and numerical methods to compute tube vibration and related wear are also presented.
Flow-Induced Vibration of a Tube Array in the Inlet Region of a High Performance Steam Generator: Part 1 — Turbulence Induced Vibration
Authors: Iwase Toshihiko , Sunami Takeshi , Matsutani Kazuhiko , Nakamura Tomomichi , Mureithi Njuki W. , Tsuge Ayao , Watanabe Yoshinori , Tomomatsu Ken-ichi , Takaba Osamu 
Published: March 2022

Abstract
The flow-induced vibration problem of the tube array in a new type of steam generator in PWR nuclear power plant is examined by using a scale model test set-up. The support conditions of the measurement tubes are the primary test parameters. Test results show that when the tubes are supported according to design specifications, stability prevails, the tubes only undergoing low stress random vibration. This report presents experimental results as well as the results of an analytical data reduction procedure to determine the turbulence force spectrum. The resulting force spectrum is found to be in good agreement with published data for the turbulent force spectrum in a tube array.
This report is the first part of a two part paper. Fluidelastic instability is covered in the second part.
Two-Phase Flow Induced Vibrations of Tube Bundles With Tube Surface Boiling
Authors: Gidi A. , Weaver D. S. , Judd R. L. 
Published: March 2022

Abstract
This paper reports the results of a study of two-phase cross-flow excitation of a tube array comprised of heated tubes in Freon-11, with vapour being generated both upstream of the test array and at the tube surfaces themselves. These experiments simulate flow excitation in real steam generators more realistically.
Special cartridge heaters were arranged in a cantilevered parallel triangular array with a pitch ratio of 1.49. Tube response was monitored in a non-obtrusive way using an optical technique developed for this purpose. Experiments were conducted under isothermal conditions for comparison with similar cases in which nucleate boiling occurred on the tube surfaces. The results indicate that the effect of vapour generated at the tube surfaces is to: a) reduce the tube vibration amplitude, mainly in the transverse direction and, b) increase the void fraction needed to reach fluidelastic instability.
Stability Behavior of an Elastically Supported Rotor Considering Fluid-Structure Interaction
Authors: Mehl Volker H. 
Published: March 2022

Abstract
In the present paper a vibrational fluid-structure system is analyzed with respect to its dynamical stability behavior. In detail, an infinitely long, rigid rotor of circular cross section is considered. It is linearly elastically supported, rotates with constant speed and may perform transversal vibrations in an annulus of arbitrary gap width which is completely filled with a compressible Newtonian fluid.
For the chosen model, a boundary value problem is formulated, whereby the derivation of the equations of motion and the boundary conditions takes into consideration the full fluid-structure interaction.
Because of the absence of external load, there is a stationary state in the form of a constant-speed rotation of the inner cylinder which is in a coaxial position with the cylindrical stator. The bifurcation of the stability problem becomes obvious by introducing a separation of the dependence on the coordinates. On the one hand, so-called Taylor vortices may develop in the fluid flow, while the rotor remains in its coaxial position. On the other hand, coupled fluid cylinder vibrations may occur. In lubrication theory, this phenomenon often is called oil whip resonance. In both cases, an eigenvalue problem for the determination of the stability limit results, which depends on characteristic parameters.
Verification of Scaling Rules for Control Valve Noise by Means of Model Tests
Authors: Graf Hans R. , Ziada Samir , Rohner Rudolf , Kälin Rudolf 
Published: March 2022

Abstract
Control valves are major sources of noise in power plants and petrochemical installations. Valve noise is not amenable to theoretical models or numerical flow simulation; model tests are commonly used instead.
Scaling rules are introduced based on the thermodynamic power dissipated in the valve. Thus the reference power is only a function of flow conditions before and after the valve and is independent of valve geometry. Valves with fundamentally different design can therefore be compared directly. The scaling rules are verified with tests in flow models of different size and with compressed air and superheated steam.
The results demonstrate the importance of considering the spectral distribution of the control valve noise. Part of the noise may be generated above the audible frequency range in the model and shift to a sensitive frequency range in large scale installations. Examples are given to illustrate the importance of the spectral distribution.
Root Cause Investigation of the Centrifugal Compressor Pulsation/Vibration Problems
Authors: Motriuk Roman W. , Harvey Douglas P. 
Published: March 2022

Abstract
High frequency pulsation generated by centrifugal compressors can cause fatigue failures of the compressor internals, impair compressor performance, and damage the attached compressor piping. There are a number of sources producing pulsation in such a complex machine. The main origin of pulsation are turbulences, blade-stator interaction phenomena, secondary flows resulting in boundary layer separation, fluid solid interactions, and compressor piping interactions. Some of them are discussed in literature at large (Japikse, 1995).
This paper describes severe pulsation conditions, in certain type of radial inlet compressors, which resulted in unacceptable piping vibration, compressor impeller failures, and other compressor component failures. From the information gathered during several failure investigations and field tests, the following concepts of failure origin were considered: flow in the diffuser, impeller blade vibration, shroud geometry, impeller radial clearance, housing effects, volute cut-off design, flow through the inlet guide vanes, flow turbulence. The investigation was carried out using modal analysis tests, finite element modeling, field measurements, and compressor internal inspections. As the process of investigation followed, the predominant pulsation/vibration sources were diagnosed as high unsteady gas velocities in the diffuser and resonances in the compressor.
The results presented in this work are based on five investigated compressors, two 16 MW and three 25 MW machines. The discharge piping vibration levels constitute a benchmark for evaluation of some of the implemented modifications.
Low Frequency Acousto-Hydraulic Excitation of Anti-Surge Valve Piping
Authors: Schafbuch Paul J. , McMahon Thomas , Kiuchi Tatsuhiko 
Published: March 2022

Abstract
Low frequency piping vibration was experienced during the startup of a large natural gas compression facility. Extensive laboratory testing, field measurements, and analysis have shown that the cause is a novel form of acousto-hydraulic excitation. The anti-surge valve was the source of the pulsation that was amplified by the piping system. The frequency of the pulsation was determined by piping acoustic modes. The strength of the hydraulic instability was found to be highly dependent on the valve’s stroke.
Traditionally the turbulence generated downstream of throttling valves is considered to be a broadband source of pulsation. Special noise-abatement trims are often used to control the amplitude and spectral content of this excitation. For this phenomenon, the hydraulic instability occurs upstream of the valve’s primary restriction and the upstream piping acoustics determine the pulsation frequencies and amplification. In this particular field system, high vibrational response results from a mechanical resonance of the piping structure coincident with the acoustic pulsation frequency. Ultimately a valve plug design change eliminated the formation of the hydraulic instability and piping vibration.
Poisson-Coupling Beat in Extended Waterhammer Theory
Authors: Tijsseling A. S. 
Published: March 2022

Abstract
The axial/radial vibrations of liquid-filled pipes, excited by long-wave waterhammer, are adequately described by the so-called four-equation model. The model is based on FSI Poisson coupling, which can produce an interesting and new phenomenon: the Poisson-coupling beat. The present paper introduces this phenomenon, shows its theoretical evidence and discusses its practical consequences.
An Experimental Study of Flow Induced Noise in Counterbalance Valves
Authors: Porteiro Jose L. F. , Weber Steven T. , Rahman Muhammad M. 
Published: March 2022

Abstract
A counterbalance valve, when correctly applied to a hydraulic circuit, modulates the flow of oil when lowering a load, with a crane for example, to prevent an overrunning condition. Under some unique operating conditions, they produce a high frequency, monotone noise that can be characterized as a “squeal.” The objective of the present work is to describe a series of experiments to investigate the flow induced noise in counterbalance valves. The experimental program not only quantified the noise level, frequency, and operating envelope in which “squealing” occurs, but also led to the formation of several hypotheses in an attempt to identify the cause of this noise. These included cavitation, oscillation of valve components, and oscillation of flow within the valve. Analyses of experimental results showed that oscillation of flow is the most likely cause of the “squealing” noise.
Time-Discontinuous Stabilized Space-Time Finite Elements for Aeroelasticity
Authors: Grohmann Boris A. , Dornberger Rolf , Dinkler Dieter 
Published: March 2022

Abstract
A method for computational aeroelasticity in the time domain has been developed. Time-discontinuous Galerkin space-time finite elements have been employed for both the transonic fluid flow and the elastic aircraft wing structure. The resulting implicit time marching scheme is robust and higher order accurate.
In order to stabilize the convective term of the fluid flow and the elastic wave propagation phenomena in the structure a Galerkin least-squares term is added. For handling discontinuities, a consistent high order nonlinear shock-capturing viscosity is applied. The aerodynamics are modeled using the compressible Euler equations. Nonlinear Timoshenko beam elements are employed for the structure. The time dependent deformation of the fluid domain is modeled using space-time mappings for the FE geometry.
Based on the discretization of equal type for the fluid and the structure, an overall iterative solver strategy for the fully coupled problem is proposed. In each time step, a common loop combines the linearization of the fluid, structure and their coupling conditions. The iterative solution of the resulting linear subproblems is partly done by multigrid methods.