bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Fluid-Structure Interaction Using the Sensitivity Equation Approach
Authors: Bhaskaran Rajesh , Berkooz Gal
Published: March 2022

A methodology for the optimization of coupled fluid-structure systems that couples flow and structural analysis codes without requiring iteration between the two codes is presented here. This method is valid in the nonlinear transonic and high-alpha regimes. It requires the sensitivity of the flow solution to perturbations in the geometry, in addition to the flow solution for the undeformed configuration. The flow solution for the base configuration and its sensitivity to geometric parameters are generated and transferred to the finite-element structural code. The structural code then solves the direct and sensitivity problems for the coupled fluid-structure system using a modified stiffness matrix. Results for the direct problem axe presented for the static aeroelastic effects on a wing section in inviscid transonic flow. The wing section is mounted through a torsion spring, in which case the geometry variation is due to deformation as well as rotation about the hinge point. The displacements show the expected aeroelastic relief effect due to the flexible loads increment. Both the flow sensitivity and the sensitivity of the coupled fluid-structure system are calculated using the sensitivity equation or direct differentiation approach. The flow sensitivity calculation is implemented by altering an existing flow code, CFL3D from NASA Langley. Implementation of optimization of the coupled system is being performed using the commercial C++ class library, PDESolve. Code snippets are presented to illustrate that an object-oriented library like PDESolve significantly reduces the effort in implementing the direct and sensitivity solutions.
Exploration of Flow-Induced Vibration at Low Mass and Damping
Authors: Gharib Mohammed R. , Shiels Douglas G. , Gharib Morteza , Leonard Anthony , Roshko Anatol
Published: March 2022

Elastically supported cylinders in cross flow are investigated experimentally and by numerical simulation. For very low values of cylinder mass ratio, it is found that the oscillation frequency is controlled by vortex shedding, with no lock-in to the mechanical frequency. In the numerical simulations the systems studied have zero mass and damping. A range of values of spring constant, including zero, is investigated at Reynolds number 100. It is found that the oscillation frequency stays in a narrow range 0.15 < fd/U∞ < 0.2 and the amplitude is in the range 0.4 < A/D < 0.6, eventually decreasing at large values of spring force.
A Numerical Study of Oscillatory Flow Around Circular and Square Cylinders
Authors: Okajima Atsushi , Yasuda Takahiro
Published: March 2022

The flow patterns around and the forces acting on an oscillating bluff body submerged in a fluid at rest have been studied by numerical simulations. An ALE (Arbitrary Lagrangian-Eulerian) finite difference method has been employed to simulate the flow around an oscillating bluff body, e.g., a circular cylinder and a square one, submerged in a still water. Simulations have been carried out under the assumption of 2- and 3-dimensional, unsteady, incompressible and viscous flow. The results predicted by numerical simulations are compared with our recent results of measurements of fluiddynamic forces on and flow-visualized patterns around a bluff body that is set in a planar oscillatory flow generated by a U-tube water tank up to Keulegan Carpenter (KC) numbers of 30 and at a value of β of 95 and 153. Although flow-patterns around a bluff body are complicatedly produced by both the vortex-shedding from a bluff body and the planar oscillatory flow, the major vortex-shedding regimes observed in experiments, flow pattern of “3-dimensional structures” at low KC numbers, “transverse street” and “double pair” all can be successfully reproduced in the present simulations, and there is good agreement between the simulated and measured flow patterns. Notable differences are also confirmed for flow configurations around a bluff body with a different shaped-section, e.g., a circular section and a square one. There is found to be good agreement also between the predicted and measured in-line forces, i.e., the values of drag and inertia coefficients, CD, CM, represented by the well-known Morison’s equation and the fluctuating transverse force (lift force) CL across a range of KC values. Furthermore, it is noteworthy that the values of transverse force depending on KC numbers correspond well to the process of flow pattern variation.
Test Line Assessment of Mechanical Power Flow in Overhead Conductors and Efficiency of Damping Devices
Authors: Leblond André , Van Dyke Pierre , Bibeau Louis-Philippe , Hardy Claude
Published: March 2022

This paper deals with a method for evaluating the flow of vibration power in single overhead conductors along a full-scale test line. Aeolian vibrations of these conductors are represented by two opposite-moving traveling wave trains which convey vibration energy. The method leads to the determination of vibration power flow as well as the spectral content of these waves. Whenever a damping device is attached to the conductor, an average traveling wave reflection coefficient can be calculated, yielding the damping device efficiency. The efficiency of three different devices is calculated: a Stockbridge-type damper, a bretelle damper and a typical suspension clamp. The magnitude of the inherent error in the method is also evaluated.
Numerical Study on Aeroelastic Behavior of a Circular Cylinder With Two Degrees of Freedom
Authors: Tamura Tetsuro , Hayakawa Akira , Okada Ray
Published: March 2022

When a circular cylinder is transversely set in fluid flows, various kinds of oscillations in the in-line as well as the cross-flow direction occur due to the aerodynamic forces, which are mainly induced by periodic vortex sheadings. In case of large amplitude, an oscillating cylinder interacts with flows close to the cylinder surface and generates the distinct vortex shedding patterns. We numerically simulate the aeroelastic behaviors of a circular cylinder. Namely, a cylinder is elastically mounted for both in-line (x) and cross-flow (y) directions, therefore can translationally oscillate in any direction in uniform flows. We examine the aeroelastic characteristics in the in-line and the cross-flow vortex-induced oscillations, and relations among different types of modal motions of a circular cylinder with two degrees of freedom. It is shown that, with regard to the response characteristics, computational results based on three-dimensional simulations agree with the experimental results. In order to clarify the mechanism of the vortex-induced oscillation, we also investigate flow structures under oscillation, for example, the behaviors of separated layers from the cylinder and their following process of vortex formation in the near wake.
Nonlinear Galerkin Methods Applied in the Dimension Reduction of Vibrating Fluid Conveying Tubes
Authors: Steindl A. , Troger H. , Zemann J. V.
Published: March 2022

In this paper we use the nonlinear Galerkin method to reduce the infinite dimensional system describing the oscillations of a fluid conveying tube to a finite low dimensional system. In fact we are able to replace a system of nonlinear partial differential equations by a set of nonlinear ordinary differential equations which are the amplitude equations of the critical modes. Three important problems are addressed in this respect. First, the choice of the form of the critical modes (ansatz functions), second the choice of the number m of the critical modes and finally the construction of the reduced system. For the latter point the so-called approximate inertial manifold (AIM) theory is used. Its explanation is one of the central goals of this paper.

By means of numerical simulations for large amplitude oscillations of a fluid conveying tube we compare the results of various choices of ansatz functions and various numbers m. Further we compare the inertial manifold approximation with the flat Galerkin method which usually is used by engineers.
Nonlinear Lateral Vibration of a Vertical Fluid-Conveying Pipe With End Mass: Effect of Horizontal Excitation at the Upper End
Authors: Yoshizawa Masatsugu , Watanabe Masanobu , Hashimoto Kouji , Takayanagi Masaya
Published: March 2022

The flow-induced vibration of a vertical cantilevered pipe with an end mass, is examined for the case that the upper end of the pipe is excited periodically in a horizontal direction. The fluid velocity of the axial flow in the pipe is over the critical value, above which the nonplanar pipe vibration is self-excited due to the internal flow. First, the effect of horizontal excitation at the upper end of the pipe is discussed with the nonlinear coupled equations governing the nonplanar pipe vibration. Second, the experiments were conducted with the silicon rubber pipe conveying water, and the spatial behaviors of the pipe were observed using the image processing system.
An Inverse Method for the Identification of a Distributed Random Excitation Acting on a Vibrating Structure: Part 1 — Theory
Authors: Granger S. , Perotin L.
Published: March 2022

In many practical situations, it is difficult, if not impossible, to perform direct measurements or calculations of the external forces acting on vibrating structures. Instead, vibrational responses can often be conveniently measured. This paper presents an inverse method for estimating a distributed random excitation from the measurement of the structural response at a number of discrete points. Part 1 is devoted to the presentation of the theoretical development. The force identification method is based on a modal model for the structure and a spatial orthonormal decomposition of the excitation field. The estimation of the Fourier coefficients of this orthonormal expansion is presented. As this problem turns out to be ill-posed, a regularization process is introduced. The minimization problem associated to this process is then formulated and its solution is developed. Part 2 is devoted to the application of this force identification method to a practical flow-induced vibration problem.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Extension of Dynamic Wake Models for Moderate to High Reduced Frequencies
Authors: Peters David A. , Karunamoorthy Swami , Sobol Michael
Published: March 2022

The flow field around a lifting rotor in hover or forward flight is represented by a matched expansion that includes an inner expansion (near the blade chord) and an outer expansion that encompasses the rotor disk. The inner expansion is expanded in Glauert variables and is completely unsteady. It is driven by blade motions and the global flow-field variable λ0 which is provided by the outer expansion. The outer expansion is in terms of rotor harmonics and radial Legendre functions (which are polynomials in r− on the blade). It is driven by the time-rate of change of bound circulation as provided from the inner expansion. Together, these form a robust convergent expansion of the rotor flow field that is good over a broad range of frequencies.
Unsteady Aeroelastic Simulations for Airfoils
Authors: Guilmineau E. , Queutey P.
Published: March 2022

Unsteady flowfields around airfoils pitching or/and plunging are investigated. The objective of this study is to test the ability of our computational code to predict unsteady fluid/structure interaction in the context of the incompressible Navier-Stokes equations. A physically consistent method is used for the reconstruction of velocity fluxes which arise from discrete equations for the mass and momentum balance. To validate the code, a dynamic-stall case is presented. Different cases in fluid/structure interaction are studied. Firstly, we examine the case where the airfoil have only a single plunging degree of freedom. Then, the airfoil can just pitch about the mid-chord. Endly, the airfoil motion consits in plunging and pitching.
Modeling and Control of Martensitic Phase Transitions in Shape Memory Alloys
Authors: Bubner Nikolaus
Published: March 2022

In order to describe phase transitions in shape memory alloys we develop a thermodynamically consistent Landau-Ginzburg model which takes into account an interfacial energy. Ingo Müller conjectures an interfacial energy to be responsible for the hysteresis loops found experimentally. We outline the determination of the physical parameters and present our numerical simulations which agree with the experiments performed by Müller and his co-workers. As an application we will consider control problems, for instance the problem of damping the vibration of a thin rod by heating and cooling.
Investigation of the Quasi-Static Potential of Recurve Actuator Elements
Authors: Ervin James D. , Brei Diann
Published: March 2022

Because most strain generating materials, such as piezoelectrics and electrostrictives, produce small deflections with large forces, some means of strain amplification is often employed to tailor the output of the actuation system to match the need of the application. Various external and internal leverage devices have been developed to amplify strain; however, these devices are commonly inefficient due to transmission losses and can be difficult to pack into constrained application volumes. A Recurve actuator architecture has been designed which amplifies direct material strains and allows for construction of highly packable, high energy density actuator arrays. The Recurve architecture enables arrays that can be tailored to produce specific force and displacement output and can be configured in a variety of ways to make efficient use of available design space. This paper describes a Recurve actuator architecture and presents a quasi-static model relating voltage, force, and deflection along with experimental results for fundamental Recurve actuator elements.
Adaptive Health Monitoring Concepts for Spot-Welded and Weld-Bonded Structural Joints
Authors: Giurgiutiu Victor , Rogers Craig A. , Chao Yuh Jin , Sutton Michael A. , Deng Xiaomin
Published: March 2022

The health monitoring of structural joints is a major concern of the engineering community and needs to be addressed with the proper consideration. Among joining techniques, the spot welding and weld-bonding (spot weld + adhesive bonding) methods are of great interest in a number of industries. Spot welding is the traditional assembly method for steel-based automotive structures, while weld-bonding is a novel technique that combines the stiffness and productivity benefits of adhesive bonding with the proven-technology attributes of spot welding. Future trends in the design and construction of vehicular structures indicate a strong diversification of material usage, with aluminum and polymeric composites projected to play a major role. While aluminum is amenable to both spot welding and adhesive bonding, composites will, most likely, be entirely adhesive bonded. Hence, the trends towards weld-bonding and adhesive bonding are clearly visible.

The paper first presents a short review of the present trends in joining techniques with special emphasis on those in present and future use in the automotive industry. This will be followed by a short review of the existing non-destructive evaluation (NDE) techniques that may be applicable to the health monitoring of spot welded and weld-bonded structures. Next, novel concepts of health monitoring utilizing an adaptive structures approach are presented. Laser ultrasound techniques; tagged adhesive methods; dielectric response techniques; electric potential methods, etc. are briefly mentioned.

Particular emphasis is placed on the electro-mechanical impedance method. This novel method is described in some detail. The electro-mechanical impedance method utilizes the coupled electro-mechanical response of piezo-electric interrogators (sensor-actuator crystals) intimately bonded to the monitored structure. An array of such structural interrogators can be envisaged to monitor the incipient local damage and crack growth in spot-welded and weld-bonded structures. Preliminary proof-of-concept demonstration tests performed with this method have shown remarkable features and ease of utilization.
Active Noise Control of Piston-Cavity Systems
Authors: Baz A.
Published: March 2022

Sound propagation in one-dimensional piston-cavity systems is controlled using Active Compressional Damping Treatments (ACDT). The treatments rely in their operation on a classical Den Hartog damper system whose dynamics are controlled in response to the sound pressure level inside the cavity. The interactions between the piston, acoustic cavity and the controller are modeled using the classical impedance approach as well as the finite element method. The developed models are used to predict and compare the sound pressure fields developed inside the cavity for pistons with and without the ACDT treatments. Comparisons are also made when the pistons are treated with conventional Passive Compressional Damping Treatments (PCDT) which are ACDT operating in their open-loop mode. The obtained results suggest the effectiveness of the ACDT concept in attenuating the sound propagation inside cavities and its potential in controlling the sound pressure fields inside three-dimensional cavities.
Host-Active Component Interactions and Performance Predictions
Authors: DeGiorgi V. G.
Published: March 2022

The performance of an integrated smart material or device is dependent on the combined performance of active and passive components. Material and geometric interactions often result in a device with complex performance characteristics. Therefore, in the design of a device, computational models which incorporate active and passive materials are a valuable tool. The present work tracts the analyses performed using such models during the design of a smart panel designed for acoustic quieting. Emphasis is placed on structural integrity and total surface displacement achieved by the device.
Experimental Investigation of Composites With Piezoelectric Actuation and Debonding
Authors: Seeley Charles E. , Chattopadhyay Aditi
Published: March 2022

Piezoelectric transducers can be used as sensors and actuators for vibration reduction in composite structures. Debonding at the transducer-laminate interface results in significant changes to the dynamic response and control authority. This important issue is studied in the current work. Composite specimens with surface bonded piezoelectric transducers were constructed with varying stacking sequences and debonding lengths. Closed loop control was implemented using an analog circuit. Experimental results were obtained for both open and closed loop frequencies and damping ratios. The results correlate well with a newly developed higher order based theory for modeling composites with debonded piezoelectric transducers. Significant changes are observed in the open and closed loop frequencies and damping ratios as a result of debonding.
Optimal Size and Location of Piezoelectric Actuator/Sensors: Practical Considerations
Authors: Aldraihem Osama J. , Singh Tarunraj , Wetherhold Robert C.
Published: March 2022

In this paper, we address the problem of obtaining the optimal size and location of piezoelectric actuator/sensors. An optimization problem is formulated for a general beam which has arbitrary boundary conditions and may have as many piezoelectric actuators as desired. The proposed optimization criterion is based on the beam modal cost and modal controllability. If the size of the actuator is unbounded, it frequently is optimal if it covers most if not all the length of the beam. This is not realistic, since there are cost, weight, and space factors to be considered. By adding a penalty term to the criterion, the size of the actuator/sensor can be reduced to a practical and reasonable size. Thus there is no need to pre-select the size of the actuator/sensor. The optimal size and location for beams with various boundary conditions are determined for a single pair and for two pairs of actuators. The results in this paper are in very good agreement with those reported by other investigators. A comparison is also made between the performance of two pairs of actuators and the performance of a single pair. The improvement in performance with two pairs is quantified.
Virtual Reality Assisted Measurement of In-Vivo Cervical Spine Kinematics
Authors: DeFrate Louis E. , Doehring Todd C. , Nishida Kotaro , Kang James D. , Gilbertson Lars G. , Woo Savio L.-Y.
Published: March 2022

In-vivo biomechanical studies of cervical spine movements are useful for defining “kinematic envelopes” of motion. Data are readily available on the ranges-of-motion of the cervical spine in flexion/extension, left/right lateral bending, and left/right axial rotation [1]. There is increasing evidence that “combined movements” may also be of clinical importance [2,3,4]. In this study, we tested the hypothesis that axial rotation limits active flexion/extension of the cervical spine. We used a specially developed measurement system featuring a 3-D magnetic tracking device with virtual reality technology that enables subjects to perform combined movements that would otherwise be difficult to achieve.
Standing Assist Device
Authors: Murphy Benjamin , Mickens LaKeshia , NeSmith Leslie
Published: March 2022

People confined to wheelchairs often find that they cannot reach things that are easily reached by those who can stand. They also have a tendency to have more gastrointestinal problems than other people. In order to alleviate some of these problems, a standing assist device was designed and built, for under $1,000, to add to the frame of a manual wheelchair. The device allows the user the ability to reach things that were out of reach. It also allows the user to stand, alleviating many causes of gastrointestinal problems. The design was evaluated by a person with paraplegia.
Not Viscous Drag but Matric Forces Are Responsible for Skin Barrier Function
Authors: van Kemenade Patricia M. , Huyghe Jacques M. , Douven Lucien F. A.
Published: March 2022

The outermost layer of the skin, the stratum corneum is only about 20 microns thick, yet plays an important role in preventing an excessive loss of body fluids to the dry environment. By damaging the stratum corneum (mechanically or chemically) the transepidermal water loss (TEWL) increases. For instance removing the whole stratum corneum by stripping the skin with adhesive tape increases the water loss by 10 times (Lo et al., 1990), and after two successive exposures of skin to a detergent solution water loss is almost twice the basal value (Barel et al., 1995).
Overview of Respiratory System Clearance Mechanisms
Authors: Krumpe Peter E.
Published: March 2022

Air breathers require convective ventilation for gas exchange to occur. However in the process of breathing the lung must clear inhaled particulates, bacteria, maintain a barrier against the outside, and humidify and warm inhaled air.
Lung-Diaphragm Model of the Respiratory System for Parameter Estimation Studies
Authors: Macia Narciso F. , Dorson William J. , Higgins Walter T.
Published: March 2022

Often respiratory models exclude the diaphragm input and its associated dynamics since they are normally inaccessible. However, some parameter estimation techniques [1–3] while requiring all the inputs to be known, subtract the inputs that are not accessible through measurement. This approach permits the identification of all parameters even though all the inputs are not available.
Hydrogel Based Artificial Heart Valve Stent
Authors: Hui Andrew J. , Duncan Anthony C. , Wan W. K.
Published: March 2022

Hydrogels have many medical applications. In this particular case, it is proposed to fabricate a heart valve stent from polyvinyl alcohol (PVA). The present heart valve stents are made of rigid materials which do not mimic the natural important mechanical properties of the aortic root such as expansibility1. We propose a new heart valve stent which can better mimic the natural mechanical properties of the aortic root.