bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation of single gas bubbles under shear flow conditions
Authors: Lakshmanan Peter , Ehrhard Peter 
Published: March 2010

AbstractDisperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break‐up or coalescence in different systems can be crucial for the process design. Usually the flow experienced by bubbles is not uniform but sheared. Under shear‐flow conditions bubbles develop a lift force perpendicular to the flow direction. In the present work direct numerical simulations are applied to examine the dependency of the lift force on the shear rate for bubbles in pure liquids. A level‐set based volume‐tracking method is implemented into the CFD‐code OpenFOAM, to follow the free interface of the gas bubble. Results show good agreement with available experimental results from single bubbles in a rotating chamber. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of incompressible viscous flows in complex geometries by a velocity correction method.
Authors: Kosma Z. , Motyl P. 
Published: March 2010

AbstractA method for simulation of viscous flows in complex geometries by resolving the Navier‐Stokes equations with the use of velocity correction procedure is developed. Its virtue lies in the simple description of the flows in terms of primitive variables, such as velocities and pressure, and in its algorithmic simplicity. Decoupling the pressure and velocity reduces the problem to the solution of a sequence of simpler problems. With this method some auxiliary velocity field is found and the projection into the divergence‐free space via the solution of a Poisson equation for some form of the pressure is performed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of viscous flow phenomena in a rotating system
Authors: Zucht Andre , Böhme Gert , Müller Andre 
Published: March 2010

AbstractIn this work we have investigated viscous flow in a rotating system. The system consists of a horizontally oriented cylindrical drum rotating around the center and a fixed plate as a scraping internal tool. By this plate the inner volume is divided into two separate chambers. No mass transport between the chambers can take place. The drum is completely or partially filled with a highly viscous, optically transparent silicon oil. In the second case the remaining space is filled with air as a passive phase. Depending on the settings in the system, which are the rotational speed of the drum, material properties of the liquid and the volume ratio of the two phases, different flow phenomena can be observed [1, 2]. For the characterization of the flow dimensionless ratios given by the Reynolds number Re, the Froude number Fr, the Capillary number Ca and the volumetric filling degree F are used. The system is investigated applying the experimental method of Particle Image Velocimetry (PIV) as well as suitable models of Computational Fluid Dynamics (CFD). The goal of this investigation is to identify the velocity fields in the liquid phase for a better understanding of the observed phenomena. The results obtained by the different methods are presented and discussed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linear stability analysis of oscillating Ekman boundary layers
Authors: Withalm Martin , Röper Jasmin , Hoffmann Norbert P. 
Published: March 2010

AbstractThe analysed Ekman layer is generated in a fluid layer rotating around an axis normal to its two bounding rigid plates. One of the plates is stationary, the other moving at certain Reynolds numbers. An additional oscillation is added to the moving plate at different amplitudes and frequencies. The linear stability of this system is determined via a Floquet analysis and a Galerkin‐approximation of the corresponding Navier‐Stokes‐Equations. If the frequencies of the oscillations are small the critical Reynolds numbers of the Type I and Type II instabilities do not differ much from steady Ekman layers. Also for a purely oscillating system the critical values of the instabilities are almost consistent with those for a steady system. Interestingly, for higher frequencies the Type II instability does not appear any more. Instead the boundary layer becomes unstable only in terms of a Type I instability. In comparison with findings of other authors these results seem to be quite reasonable. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On solitary waves in one‐dimensional microstructured solids
Authors: Randrüüt Merle , Braun Manfred 
Published: March 2010

AbstractIn a microstructured solid with nonlinearities in macroscale and microscale, the propagation of 1D waves is governed by an extended KdV equation, which admits asymmetric solitary waves. An approximate solution is presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aero‐Acoustic Optimisation of Airflow Components in Gas Turbines
Authors: Schroeder G. , Uffrecht W. , Odenbach S. 
Published: March 2010

AbstractThere is always a great interest in the improvement of the efficiency of gas turbines. This requires the reduction of energetic losses like pressure losses induced by vortices, turbulence and secondary flow. In the current investigation, effects caused by aero‐acoustic oscillation are of interest. The possibility to control these effects or to make them usable has several advantages, for example reducing pressure losses, reducing noise, and influencing the heat transfer and charging effects. This concerns potentially oscillatory flow systems in gas turbines like pipes, cavities and annuli. In particular annuli can not be considered theoretically using one‐dimensional pipe acoustic. The start of oscillation occurs due to turbulent shear stress, solid oscillating surfaces and time fluctuating pressure fields as well as thermal stimulation. This study focuses on the impact of aero‐acoustic oscillation caused by shear stress and rotating pressure fields on the through flow. A numerical study of axial, radial and circumferential acoustic eigen‐modes and a time harmonic analysis have been done with several boundary conditions. The achieved results have to be proved in a further experiment. An improvement in the aero‐acoustical design of gas turbine flow components will be possible thanks to the results gained from both the numerical study and planned experiment. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental Feasibility Study for Guided Wave Propagation
Authors: Kern Dominik , Seemann Wolfgang 
Published: March 2010

AbstractThe paper presents the work on Structural Health Monitoring (SHM) which is now one of the most interesting subjects. Guided propagation of mechanical waves in elastic bodies can be applied in analogy to active phased radar antennas for electromagnetic waves. An array of bonded piezoelectric transducers can generate directed mechanical waves. In the current state of this work experiments on a beam are conducted in order to verify a mathematical model based on integral transform methods. Further experiments for plates and laminates have been designed and checked for feasibility of the mechanical and the electrical implementation. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lamb wave propagation using Wave Finite Element Method
Authors: Ahmad Zair Asrar Bin , Perez Juan Miguel Vivar , Willberg Christian , Gabbert Ulrich 
Published: March 2010

AbstractSome of the available techniques for Lamb wave propagation simulation are the Finite Element Method (FEM), the Boundary Element Method and the Finite Difference Method. The FEM is the best method when complex damage, geometry or boundary is involved. However, high Lamb wave frequency requires very small element size thus high computational cost in FEM analysis. By using the existence of periodicity in plates, an attempt to reduce this computational cost is done using Wave FEM. The applicability of this method to model Lamb wave propagation in plate is first assessed in this paper for the 1‐D wave propagation and compared with FEM explicit method. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relaxation dynamics of the rheological properties of ferrofluids
Authors: Borin Dmitry , Odenbach Stefan 
Published: March 2010

AbstractWe studied experimentally the shear stress relaxation of two different ferrofluids under the action of an external magnetic field by stepwise changes of shear rate. It has been found that ferrofluids able to form significant structures under the influence of an applied magnetic field show a slow relaxation phenomenon. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Forced Alveolar Flows and Mixing in the Lung
Authors: Borer David , Rösgen Thomas 
Published: March 2010

AbstractThe air flows deep inside the lung are not only important in gas exchange processes but they also determine the efficiency of particle deposition and retention. The study aims at quantifying the relative influence of different flow components in the transport of small particles in alveolar geometries such as convective breathing patterns, wall movement, gravitational settling and Brownian motion. In addition, the possibility and efficiency of external forcing is studied, relying on the mechanism of internal acoustic streaming. A viscous oscillating boundary layer flow is converted into a steady, viscosity‐independent bulk motion which is very efficient at low Reynolds numbers. The streaming can be controlled by external parameters (excitation amplitude, frequency, beam shape) and may thus be of diagnostic and therapeutic relevance. Numerical simulations are performed to analyze the flow patterns in 3D model geometries and to measure deposition rates. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the existence for viscoelastodynamic problems with unilateral boundary conditions
Authors: Petrov Adrien , Schatzman Michelle 
Published: March 2010

AbstractThis note deals with a damped wave equation and the evolution of a Kelvin–Voigt viscoelastic material, both problems being subject to unilateral boundary conditions. The functional properties of all the traces are precisely identified through Fourier analysis, which implies the existence of a solution satisfying almost everywhere the unilateral boundary conditions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of a siped tire tread block by an Euler‐Bernoulli beam
Authors: Ripka Stefan , Wangenheim Matthias 
Published: March 2010

AbstractWinter tires earn more and more attention due to the increasing awareness of safety aspects also in emerging markets like Russia and China. Besides the rubber compound the siped geometry of the tread blocks is essential. The mechanical behaviour of sliding lamellas is modeled with the beam theory of Euler–Bernoulli. In this contribution the siped tread block model will be experimentally verified and first simulation results will be presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and numerical analysis of the cutting process
Authors: Bohdal Lukasz , Kukielka Leon 
Published: March 2010

AbstractThe course of the cutting process with using wedge‐shaped tool is presented in the paper. To observe the kinematics of flowing of material, the states of displacement and deformations for any moment the model investigations were done. Some results of the analysis, which can be used in designing and optimization of the process, are presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology optimization based on the first optimization steps strain energy analysis.
Authors: Kutylowski Ryszard , Szwechlowicz Marek 
Published: March 2010

AbstractThe paper presents the algorithm for obtaining “the near optimal” topology very fast, based on the first optimization steps strain energy analysis. The objective function is the compliance of the structure. It is equal to the strain energy and it is minimized under the body mass constraints. Because the material density is proportional to the strain energy accumulated in discrete material point, the identification of more and less effort domains especially for the first optimization steps let analyse the structure from the topology point of view. This identification is the base of relative faster finding out material domains and void domains within the design domain which leads to the topology, which is very similar to the optimal topology even from the strain energy level point of view. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An approach for optimization of loading cycles of hydraulic mining excavators
Authors: Flores Geu , Xia Shuxian , Kecskeméthy Andrés , Pöttker Alois 
Published: March 2010

AbstractThe present paper describes an optimization multi‐stage approach for computing the optimal loading cycle of a heavy weight excavator along a predefined trajectory under dynamic constraints such as maximal ensuing forces, accelerations, and maximal allowed hydraulic power. The approach involves the use of splines of 3rd and 5th order for smooth interpolation of the spatial trajectory up to the level of linear and angular accelerations, as well as an SQP optimization routine to find the optimal end‐effector motion law along the trajectory, which finally leads to strokes and pressures at the hydraulic actuators as a function of time. The approach can also be extended to other multi‐body systems following a predetermined trajectory. The solution scheme can be included in a more general optimization routine aiming to optimize the trajectory itself. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal PID control in case of random initial conditions
Authors: Schacher Michael 
Published: March 2010

AbstractThe aim of this presentation is to construct a robust optimal PID feedback controller, taking into account stochastic uncertainties in the initial conditions. Usually, a precomputed feedback control is based on exactly known model parameters. However, in practice, often exact information about model parameters and initial values is not given. Hence, having an inital point, which differs from the nominal values, a standard precomputed controller may produce bad results. Supposing now that the probability distribution of the random parameter variations is known, in the following stochastic optimisation methods will be applied in order to obtain robust optimal feedback controls. Taking into account stochastic parameter variations at the initial point, the method works with expected total costs arising from the primary control expenses and the tracking error. Furthermore, the free regulator parameters are selected then such that the expected total costs are minimized. After Taylor expansion to calculate expected cost functions and a few transformations an approximate deterministic substitute control problem follows. Here, retaining only linear terms, approximation of expectations and variances of the expected cost functions can be calculated explicitly. By means of splines, numerical approximations of the objective function and the differential equations are obtained then. Using stochastic optimization methods, random parameter variations are incorporated into the optimal control process. Hence, robust optimal feedback controls are obtained. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sparse Data Representation of Random Fields
Authors: Litvinenko Alexander , Matthies Hermann G. 
Published: March 2010

AbstractMathematical models with uncertainties are often described by stochastic partial differential equations (SPDEs) with multiplicative noise. The coefficients, the right‐hand side, the boundary conditions are modelled by random fields. As a result the solution is also a random field. We offer to use the Karhunen‐Loève expansion (KLE) to compute a sparse data format for the fast generation and representation of these random fields. The KLE of a random field requires the solution of a large eigenvalue problem. Usually it is solved by a Krylov subspace method with a sparse matrix approximation. We demonstrate the use of both, the sparse hierarchical matrix format as well as the low‐rank Kronecker tensor format. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Iterative numerical method for integral models of a nonlinear dynamical system with unknown delay
Authors: Tynda Alexander N. 
Published: March 2010

AbstractThis paper is devoted to the construction of iterative numerical algorithm for the systems of nonlinear Volterra‐type equations of the special form related to the Vintage Capital Models (VCMs). One of the unknown functions of these equations is in the lower limit of integration. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blending Dual Time Stepping and Newton‐Krylov Methods for Unsteady Flows
Authors: Birken Philipp , Jameson Antony 
Published: March 2010

AbstractWe explore the idea of using nonlinear schemes as preconditioners in Newton‐Krylov schemes for unsteady flow computations. Analysis shows that left preconditioning changes the Newton scheme in a non equivalent way, leading to a stall in Newton convergence, whereas right preconditioning leads to a sound method. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical determination of heat exchanger response
Authors: Milewska A. 
Published: March 2010

AbstractIn this paper there is presented approximative calculation of the temperature of fluid in fixed point of heat exchanger and in fixed time. In presented method are used Newton‐Cotes formulas. Moreover there is evaluated the error which is made during determination of heat exchanger response. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The sensitiveness of the speed of pile displacement to speed variations of hammer in beating down process
Authors: Milewska A. , Żukowska J. 
Published: March 2010

AbstractIn this paper there is presented dynamical system described speed of pile displacement during beating down process. Its response is determined by using Heaviside operator. There is introduced the convergence with regulator in partially ordered space. There is given an answer to the question, whether the researched dynamical system describing speed of pile displacement is sensitive to hammer's speed variations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Projection‐Algebraic Scheme of Discrete Approximations for Linear and Nonlinear Differential Operator Equations in Banach Spaces
Authors: Luśtyk Mirosław , Prykarpatsky Anatoliy 
Published: March 2010

AbstractThe solution set, realizability and convergence of the projection‐algebraic method of discrete approximations for linear and nonlinear differential operator equations are studied. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chatter Vibration Surveillance by the Optimal‐linear Control of Spindle Speed and Randomly Varying Spindle Speed
Authors: Kalinski Krzysztof , Galewski Marek 
Published: March 2010

AbstractTool‐workpiece relative vibration plays principal role during the process of milling with slender ball end mills. Due to certain conditions, a loss of stability and generation of self‐excited chatter vibration will appear. The paper is devoted to a new approach towards vibration surveillance of rotating tools in modern milling machines. Dynamic analysis of a slender ball end milling process has been performed and dynamics of controlled structure is described. In order to reduce vibration level, instantaneous change in the spindle speed appears as control command, and thus the method of vibration surveillance by the spindle speed optimal‐linear control has been developed. Due to quality of machined surface being worse while milling with high tilting angle of the tool, the other method of milling with randomly varying spindle speed is presented. It allows us to maintain a high efficiency of surveillance without worsening of the machining quality. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control‐oriented Rotordynamics
Authors: Gosiewski Zdzisław 
Published: March 2010

AbstractThe rotor vibrations are coupled by many parameters: angular speed couples two radial directions, unbalance couples torsional and lateral vibrations, rotor support couples rigid body and flexible modes. Small changes of these parameters strongly influence the rotor dynamics. The full analysis of the rotor coupled vibrations is much simpler when we can divide the system into smaller subsystems. In this case the calculations are simplified and we have deep insight into mechanisms leading to good or bed behaviour of the rotor motion. It is particularly important in the case of the rotor working in the wide range of the angular speeds. For the vibration analysis the methods known from control theory can be applied.The proposed approach was testified in the paper on the simple 3‐mode rotor model. The torsional vibrations were separated from the lateral vibrations and a feedback among the subsystems was established. The subsystems are coupled by rotor unbalance and root locus method allows to show the critical values of the unbalance which destabilize rotor motion for different angular speeds. The lateral vibrations are stabilized by angular speed and again it is possible to find how big value of the rotor speed is sufficient to stabilize the rotor motion. Such analysis of the rotor vibrations appeared very useful for the choice of the control strategy. It indicated such control laws which amplify the stabilizing mechanisms in the rotor dynamics. Such procedures can also lead to the energy saving control laws. In the case of the lateral vibrations there were considered four control strategies. And these strategies were compared to indicate optimal one. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Motion planning for planar bipeds using flatness: the single support phase
Authors: Krause Matthias , Rudolph Joachim , Woittennek Frank 
Published: March 2010

AbstractTrajectory planning and control of planar motions of biped robots is considered. The robot is modeled as a hierarchical structure of rigid links with rotational joints, which may be seen as a pendulum tree. Motors are available at all rotational joints. However, by the absence of control torques at the contact points with the ground, the system is underactuated. It is shown how differential flatness and time scaling can be helpful for the design of walking motions. Emphasis is put on the single support phase, when the robot touches the floor at a single point. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the mobile platform motion optimal control at energy performance index
Authors: Kalinski Krzysztof , Mazur Michal 
Published: March 2010

AbstractThe paper presents a method of optimal control of the mobile robot on example of the 2‐wheel mobile platform. The robot investigated has non‐holonomic constraints. Mathematical model of 2‐wheel mobile platform is characterized by finite number of nonlinear differential equations. The presented method of control is minimizing velocity and position errors. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Noisy and chaotic conditions of a pendulum motion
Authors: Borowiec Marek , Litak Grzegorz 
Published: March 2010

AbstractThe effect of noise on the rotational mode of a pendulum which is excited kinematically in vertical direction has been analyzed. We have applied the multifractal analysis to distinguish chaotic and noisy solutions in transitions from the oscillations to rotations motion of a pendulum. During increasing the noisy disturbance of the system we analyzed the basic multifractals criteria of the system as correlation and complexity. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)