bluuebunny/crossref_metadata_2025_split huggingface dataset:
Approach for Adaptive Sound Power Minimization of Elemental Sources in Theory and Experiments
Authors: Krause Uli , Sachau Delf 
Published: December 2014

AbstractLow frequency noise is a major issue in future aircraft with counter rotating open rotor engines. Passive noise treatments are bulky and heavy at these low frequencies. That is why active approaches are considered. The well known concept of destructive interference is used by state of the art active noise cancellation methods. The active systems are located closely to the noise source to cancel it. The microphones used for pressure minimization are in the near sound field of the noise source where active and reactive sound intensity are present. The pressure based concept is minimizing just the potential part of the acoustic energy. A new approach is proposed in this paper. It minimizes directly the net flow of acoustic energy that is transmitted into an interior. Simulation results showed that a proper estimation of acoustic power output is achieved by measuring sound intensity at a single point directly on the central axis of each secondary source. The innovative energy based active control approach (TASPM) has also successfully been validated in a laboratory environment. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of defects to the band‐gaps generation
Authors: Munteanu Ligia , Popescu Mihaela 
Published: December 2014

AbstractEffect of defects to the band‐gaps generation in sonic composites is investigated in this paper. Acoustic scatterers are composed by piezoceramic hollow spheres of functionally graded materials. Defects are vacancies or foreign interstitial atoms which are supported by the interfaces between the hollow spheres and the matrix. The presence of defects in sonic composites is related to the generation of localized modes in the vicinity of the point defect with a significant evanescent behavior of the waves outside the defect point. As result, the full band‐gap is wider than in the case of no defects. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uncertainty Analysis for Crack Detection in Cylindrical Waveguides
Authors: Schaal Christoph , Hanss Michael 
Published: December 2014

AbstractCable structures usually consist of several individual wires, where each wire acts as a waveguide, guiding waves over long distances. The influence of uncertainty on a crack detection algorithm based on the Hilbert transform is investigated in this work. Not only is vagueness in calculated group velocities considered, but also imprecision in the algorithm's parameters. Moreover, the validity and robustness of the considered algorithm with applied uncertainty is discussed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of drying and wetting on the wave propagation in partially saturated soils
Authors: Albers Bettina 
Published: December 2014

AbstractThe propagation of sound waves in Del Monte sand filled by an air‐water mixture is studied by a linear model. Even if it does not include an operator to describe the hysteresis of the capillary pressure curve, hysteresis is accounted for: the wave analysis is performed for the two limit cases of main drying and main wetting. In the van Genuchten law both drying and wetting data are applied. Four waves appear: one transversal wave and three longitudinal waves. For the waves driven mainly by the skeleton it could be expected that the influence of consideration of the hysteresis in the capillary pressure curve is negligible. In contrast, the numerical results for the waves driven by the pore fluids exhibit a smaller influence than expected. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Frequency‐dependent properties of multiphase materials: origins, needs, and effective use in geophysics and modern synthetic materials.
Authors: Kurzeja Patrick S. , Steeb Holger 
Published: December 2014

AbstractDynamic processes in multiphase materials, e.g., fluid‐filled sandstones or bones, are described by models that include frequency‐dependent properties. The origin of such properties is introduced as an averaged representation of frequency‐dependent microscale motions. In addition to classical frequency‐dependence of fluid flow, the influence of weak, high‐porosity materials and fluid‐fluid interfaces is discussed. The relevant characteristic numbers are contrasted and specific situations are demonstrated, in which frequency dependence has to be considered or not. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Damping of water hammer oscillations – comparison of 3D CFD and 1D calculations using two selected models for pipe friction
Authors: Riedelmeier Stefan , Becker Stefan , Schlücker Eberhard 
Published: December 2014

AbstractWater hammer calculations are important for power plants, drinking water systems and procedural facilities. In most cases, the piping systems are very big and the probability of a resonance between a part of the piping system and a hydraulic oscillation resulting from water hammer is very high. The limiting factors for the amplitudes of the structural stresses and strains are the structural and hydraulic damping. In general, one‐dimensional codes based on the method of characteristics with quasi‐steady friction models are used to calculate the hydraulic system. This results in too small damping of the pressure oscillation and thus in an overestimation of the structural loads. Two models from the literature for a more physical reproduction of the fluid damping using one‐dimensional codes are presented and compared with a quasi‐steady pipe friction model. Additionally, a three‐dimensional computational fluid dynamics simulation of a water hammer oscillation in a small pipe section including a 90°‐bend was carried out. A comparison of the results of the three‐dimensional simulation and the one‐dimensional calculations with regard to the pressure and friction velocity distributions was performed, the performance of the models was evaluated and the limits of validity were identified. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of acoustic parameters in flow fields using OpenFOAM
Authors: Schmalz Jan , Kowalczyk Wojciech 
Published: December 2014

AbstractIn the present paper a Computational Aero Acoustics approach based on Lighthill's and Curle's Acoustic Analogies was implemented in OpenFOAM 2.1.1. The novel developed OpenFOAM application solvers acousticFoam and acousticRhoFoam can be used for transient incompressible and compressible simulations respectively. The CAA approach takes High Performance Computing environment into account and realize the computation of flow and acoustic fields within the acoustical near field on one mesh only. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kinematic‐wave analysis of particle settling in tube centrifuges
Authors: Anestis Georg , Schneider Wilhelm 
Published: December 2014

AbstractThe kinematic‐wave theory of particle settling in tube centrifuges is subject to controversy. G. Anestis and W. Schneider [1] made the common assumption that the flow in a rotating tube of large length/diameter ratio can be treated in one‐dimensional approximation. Their results have been found in agreement with measurements [2], [3]. However, M. Ungarish [4] performed an analysis of the two‐dimensional settling process in the limit of vanishing particle concentration and obtained results that are not in accord with the one‐dimensional flow approximation, irrespective of the length/diameter ratio. It is the aim of the present investigation to gain a better understanding of the process. According to this analysis, quasi‐one‐dimensional kinematic waves are embedded in a two‐dimensional bulk flow that is governed by the boundary conditions at the walls of the tube. The results are compared with those of the one‐dimensional flow approximation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐Dimensional Green's Function for a Layered Isotropic Half‐space
Authors: Chen Lin , Butenweg Christoph , Klinkel Sven 
Published: December 2014

AbstractA numerical approach to calculate the Green's function for a layered half space is presented. It is based on the precise integration method (PIM), which is an efficient and accurate numerical method for the solution of one order ordinary differential equations. In the numerical implementation, the layered half space is divided into numerous mini‐layers; and the dual vector form of the wave motion equation is introduced to combine two adjacent mini‐layers/layers. The advantages of the proposed algorithm are: (a) it overcomes the exponent overflow generally encountered with employing the transfer matrix method; (b) it avoids solving the intractable transcendental functions in the stiffness matrix method and the huge matrix calculation in the thin layer method; (c) it imposes no limit to the thickness of layered strata and ensures convergence at high‐frequency range. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient simulation of wave propagation in heterogeneous materials
Authors: Joulaian Meysam , Duczek Sascha , Gabbert Ulrich , Düster Alexander 
Published: December 2014

AbstractIn this contribution we explain the core idea of the recently proposed spectral cell method, which combines a fictitious domain approach with finite elements of high order and noticeably relieves the burden of mesh generation. Moreover, it employs mass lumping techniques and significantly reduces the computational expenditure. Our studies show that the spectral cell method leads to similar results yet with less computational effort as compared to standard techniques. These properties turn the method to a viable tool for the wave propagation analysis of structures that obey a complicated geometry. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave propagation and band gaps in homogenized phononic plates — modelling by spectral decomposition
Authors: Rohan Eduard , Cimrman Robert , Miara Bernadette 
Published: December 2014

AbstractThe paper deals with analysis of the elastic waves in the Reissner‐Mindlin type of plates formed by strongly heterogeneous structures. The homogenized plate model involves frequency‐dependent mass coefficients associated with the plate cross‐section rotations and the plate deflections. Intervals of frequencies called band gaps exist for which these coefficients constituting a mass matrix can be negative, so that certain wave modes cannot propagate. A spectral decomposition based method is proposed which is suitable to compute the plate response for an external loading by periodic forces with frequencies in range of the band gaps. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient line search technique and its application to adjoint topology optimisation
Authors: Gerdes Anne , Hinze Michael , Rung Thomas 
Published: December 2014

AbstractFor the adjoint topology optimisation of a fluid‐dynamic cost functional we apply an Armijo step length selection rule in the gradient descent algorithm. To reduce the computational effort for evaluating the cost functional value in the step length prediction, the function evaluation step is performed on a coarse mesh. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Lorentz force flow meter for application at blast furnaces: design and calibration
Authors: Hernández Daniel , Karcher Christian , Thess André 
Published: December 2014

AbstractA reference Lorentz force flow meter (LFF) has been developed to measure molten steel mass flow at the end of the runner of an experimental blast furnace. It works according to the principles of Lorentz force velocimetry [1] in which a static magnetic field interacts with a liquid metal stream. The magnetic field lines are generated by an arrangement of permanent magnets and penetrate the entire cross‐section of the flow generating eddy currents and a total Lorentz force inside the melt. This force is proportional to the mass flow of the liquid metal and owing Newton's third law, there is a counter force of the same magnitude acting on the magnet system which is connected to a load cell. For accurate flow rate measurements, a “dry and wet calibration” of the LFF needs to be performed [2]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the influence of plasma DBD actuator on the flow in a rectangular channel
Authors: Procházka Pavel , Uruba Václav 
Published: December 2014

AbstractPreviously, the vortical structures generated by plasma DBD actuator working in unsteady regime were investigated in detail. The generalized model describing the behaviour of these vortices in dependency on input power parameters was introduced. This paper should reveal how the wall‐jet‐like‐flow generated by that actuator will affect the developed flow in a rectangular channel with cross‐section dimension of 250 × 100 mm. The actuator is considered in spanwise configuration where the induced flow has the same or opposite orientation as the main flow. The flow control will be tested both for steady regime and for unsteady regime. The dynamic of that complex phenomenon will be studied and results in qualitatively and quantitatively meaning will be presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Feedback Stabilization of an Oscillating Vertical Cylinder by POD Reduced‐Order Model
Authors: Tissot Gilles , Cordier Laurent , Noack Bernd R. 
Published: December 2014

AbstractThe objective of this paper is to demonstrate the use of Reduced‐Order Models (ROM) based on Proper Orthogonal Decomposition (POD) to stabilize by vertical oscillations the flow over a circular cylinder at a Reynolds number equal to 60. Since in Fluid‐Structure Interaction, the POD algorithm cannot be applied directly, we then implement the fictitious domain method of [1] where the solid domain is treated as a fluid undergoing an additional constraint. The POD‐ROM is classically obtained by projecting the Navier‐Stokes equations on a small number of POD modes. The cylinder movement is then enforced in the POD‐ROM through the introduction of Lagrange multipliers. A Linear Quadratic Regulator framework is used to determine the optimal control law, in our case the vertical velocity of the cylinder, such that the flow is stabilized. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Stokes resolvent equations in 2d exterior domains
Authors: Varnhorn Werner 
Published: December 2014

AbstractWith methods of hydrodynamical potential theory we construct a solution of the Stokes resolvent equations in 2d exterior domains with C1,α‐boundaries, 0 < α ≤ 1. The resulting system of boundary integral equations is uniquely solvable for small resolvent parameter λ and allows the limiting procedure λ → 0. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal estimates on free boundary propagation in thin‐film flow
Authors: Fischer Julian 
Published: December 2014

AbstractWe present a method for the derivation of lower bounds on free boundary propagation for the thin‐film equation, one of the most prominent examples of a higher‐order degenerate parabolic equation. In particular, we obtain sufficient conditions for instantaneous forward motion of the free boundary, upper bounds on waiting times, as well as lower bounds on asymptotic propagation rates. Our estimates coincide (up to a constant factor) with the previously known reverse bounds and are therefore optimal. To the best of our knowledge, these results constitute the first lower bounds on free boundary propagation for any higher‐order degenerate parabolic equation. Our technique is based on new monotonicity formulas for solutions to the thin‐film equation which involve weighted entropies with singular weight functions. It turns out that our method is not restricted to the thin‐film equation, but also applicable to other higher‐order parabolic equations like quantum drift‐diffusion equations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The NLS and FWI approximation make wrong predictions for the water wave problem in case of small surface tension
Authors: Sunny Danish Ali , Schneider Guido , Zimmermann Dominik 
Published: December 2014

AbstractIn has been shown in [5] that the NLS approximation makes wrong predictions for the water wave problem in case of small surface tension. We explain that the ideas used in [5] allow to show a similar result for the FWI approximation, too. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Shape and Material Nonlinearities Influences about the Internal Thermal Dissipation for Elastomer‐Based Vibration Isolators
Authors: Nastac Silviu , Debeleac Carmen 
Published: December 2014

AbstractThis study deals with nonlinear internal dissipation inside the vibration isolators based on elastomeric composites. Due to the thermal influences on mechanical characteristics occurs during the regular exploitation regime, both conservative and dissipative components have affected and the main parameters continuously change. Beside the nonlinear behaviour of the assembly containing the isolator device, these changes also affects the thermodynamic regime inside the elastomeric material. The isolator shape also affects the internal thermal dissipation state. This complex behaviour implies nonlinear mathematical models, which have to be able to simulate the realistic viscous and elastic characteristics of such composites subjected to dynamic loads. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some properties of asymptotic energy of a class of functionals of Ginzburg‐Landau type endowed with generalized lower‐order oscillatory term in one dimension
Authors: Raguž Andrija 
Published: December 2014

AbstractWe consider a generalization of the functional of Ginzburg‐Landau type studied in the paper A. Raguž: A note on calculation of asymptotic energy for Ginzburg‐Landau functional with externally imposed lower‐order oscillatory term in one dimension, Boll. Un. Mat. Ital. (8)10‐B, 1125‐1142 (2007), whereby the oscillatory term a(ε−βs) (where a ∈ L1per(0, 1) and β > 0) is replaced by a(ρεs) (where limε−→0 ρε = +∞). We describe how the expression for the rescaled asymptotic energy of such class of functionals depends on the properties of the sequence (ρε). (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of heat transfer characteristics in energy piles
Authors: Zhou Long , Masood Rao , Jovicic Vojislav , Zbogar‐Rasic Ana , Kempe Victor , Delgado Antonio 
Published: December 2014

AbstractSingle energy pile is studied numerically by both commercial code (CFX 13.0) and open‐source software (OpenFOAM). Both fluid and solid domains are simulated. The temperature distribution in the soil and fluid shows the consistency of the two software. Because of the high computational cost for the simulation of multiple piles, a simplification approach is proposed. The fluid temperatures are updated by iterative analytical calculation while the soil temperatures are simulated by conductive heat transfer equation using OpenFOAM. By this effort, the computation of the whole energy pile system is feasible. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some recent results on a free boundary problem for microelectromechanical systems
Authors: Escher Joachim , Laurençot Philippe , Walker Christoph 
Published: December 2014

AbstractThe mathematical modeling of idealized microelectromechanical systems leads to a nonlinear singular elliptic‐parabolic free boundary problem involving non‐smooth domains and depending on a parameter λ reflecting the applied voltage across the device. Recent results derived in [1,4] are presented which confirm physically important and expected features: For small λ there is (at least) one stable stationary solution and solutions to the evolution equation exist globally in time, while for large λ no stationary solution exists and the evolution equation has no global solution. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stopping Distance from Observations by Stepwise Regression
Authors: Niessner Herbert 
Published: December 2014

AbstractIn a regression equation with many terms stepwise regression allows to pick out significant terms and to exclude insignificant ones. This can be used to solve rank deficient equation systems. Yet significance is not condition. There is a rather simple method for stepwise regression starting from extended normal equations proposed by Efroymson 1960 [1] and improved by Breaux 1968 [2]. Numerically more stable methods apply orthogonal transformations (Eldén 1972 [3], Gragg‐LeVeque‐Trangenstein 1979 [4]). If symmetry is properly made use of [2, 5] the method of Efroymson is the most efficient one with respect to computing time. But reasonable results are obtained only if the terms in the regression equation are physically justified. This illustrates the search for a formula of the stopping distance derived from observations, an exercise given in [9], a book widely used on some universities. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the solution of the Fokker‐Planck equation on infinite domains using problem‐specific orthonormal basis functions in a Galerkin‐type method
Authors: Lentz Lukas , Martens Wolfram 
Published: December 2014

AbstractAbstract: The dynamical behavior of a mechanical system under random excitation can be described by its probability density function (PDF). The PDF can be determined by random sampling or directly computed as the solution of the corresponding FOKKER‐PLANCK equation (FPE). Since the class of FPE with known exact solution is very small, the solution is mostly approximated by numerical methods including finite elements, finite differences or other types of local discretization methods that are best suited for finite domains. Whilst this restriction can be desired for some models, the domain needs to be unbounded in the general case. The authors present a method of calculating a semi‐analytical approximate solution for the stationary FPE over an unbounded domain using a GALERKIN‐type method. The utilization of a problem‐specific orthonormal basis for the ansatz‐space ensures that only a small number of improper integrals needs to be computed. In fact, these computations are inexpensive and can be performed prior to the more costly algorithm that constructs the system of linear equations. The computation of the specific basis and its properties are discussed in detail. In order to demonstrate the method and its application on technical systems, the PDF for a nonlinear bistable magneto‐piezo‐electric energy harvester is calculated. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Probabilistic LCF Model for Turbo Charger Compressor of a Jet Engine
Authors: Saadi Mohamed 
Published: December 2014

AbstractWe present a probabilistic low cycle fatigue (LCF) Model for turbo charger compressor of a jet engine. This compressor is made of casted aluminum alloy (C355). This model has been implemented using the finite element method in R Language [4]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and design optimization of textiles via homogenization
Authors: Shiryaev Vladimir , Orlik Julia 
Published: December 2014

AbstractThis article deals with optimization of large structures of linear elastic material with contact modeled by Robin‐type boundary conditions. Homogenization is used to represent the structures as homogenous elastic bodies and is essential for formulation of the optimization problems, where optimization of the effective properties is considered. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)