oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2017 ( 1 )

2015 ( 29 )

2014 ( 30 )

2013 ( 29 )

Custom range...

Search Results: 1 - 10 of 374 matches for " Kilian Oberleithner "
All listed articles are free for downloading (OA Articles)
Page 1 /374
Display every page Item
Mean flow stability analysis of oscillating jet experiments
Kilian Oberleithner,Lothar Rukes,Julio Soria
Physics , 2014, DOI: 10.1017/jfm.2014.472
Abstract: Linear stability analysis is applied to the mean flow of an oscillating round jet with the aim to investigate the robustness and accuracy of mean flow stability wave models. The jet's axisymmetric mode is excited at the nozzle lip through a sinusoidal modulation of the flow rate at amplitudes ranging from 0.1 % to 100 %. The instantaneous flow field is measured via particle image velocimetry and decomposed into a mean and periodic part utilizing proper orthogonal decomposition. Local linear stability analysis is applied to the measured mean flow adopting a weakly nonparallel flow approach. The resulting global perturbation field is carefully compared to the measurements in terms of spatial growth rate, phase velocity, and phase and amplitude distribution. It is shown that the stability wave model accurately predicts the excited flow oscillations during their entire growth phase and during a large part of their decay phase. The stability wave model applies over a wide range of forcing amplitudes, showing no pronounced sensitivity to the strength of nonlinear saturation. The upstream displacement of the neutral point and the successive reduction of gain with increasing forcing amplitude is very well captured by the stability wave model. At very strong forcing (>40%), the flow becomes essentially stable to the axisymmetric mode. For these extreme cases, the prediction deteriorates from the measurements due to an interaction of the forced wave with the geometric confinement of the nozzle. Moreover, the model fails far downstream in a region where energy is transferred from the oscillation back to the mean flow. This study supports previously conducted mean flow stability analysis of self-excited flow oscillations in the cylinder wake and in the vortex breakdown bubble and extends the methodology to externally forced convectively unstable flows.
Spectral proper orthogonal decomposition
Moritz Sieber,Kilian Oberleithner,Christian Oliver Paschereit
Physics , 2015,
Abstract: The identification of coherent structures from experimental or numerical data is an essential task when conducting research in fluid dynamics. This typically involves the construction of an empirical mode base that appropriately captures the dominant flow structures. The most prominent candidates are the energy-ranked proper orthogonal decomposition (POD) and the frequency ranked Fourier decomposition and dynamic mode decomposition (DMD). However, these methods fail when the relevant coherent structures occur at low energies or at multiple frequencies, which is often the case. To overcome the deficit of these "rigid" approaches, we propose a new method termed Spectral Proper Orthogonal Decomposition (SPOD). It is based on classical POD and it can be applied to spatially and temporally resolved data. The new method involves an additional temporal constraint that enables a clear separation of phenomena that occur at multiple frequencies and energies. SPOD allows for a continuous shifting from the energetically optimal POD to the spectrally pure Fourier decomposition by changing a single parameter. In this article, SPOD is motivated from phenomenological considerations of the POD autocorrelation matrix and justified from dynamical system theory. The new method is further applied to three sets of PIV measurements of flows from very different engineering problems. We consider the flow of a swirl-stabilized combustor, the wake of an airfoil with a Gurney flap, and the flow field of the sweeping jet behind a fluidic oscillator. For these examples, the commonly used methods fail to assign the relevant coherent structures to single modes. The SPOD, however, achieves a proper separation of spatially and temporally coherent structures, which are either hidden in stochastic turbulent fluctuations or spread over a wide frequency range.
Between economic and legal analysis of incorporeal things: A critical "no" to aedilitian remedies
CG Kilian
Potchefstroom Electronic Law Journal/Potchefstroomse Elektroniese Regsblad , 2006,
Abstract: This article analyses the dictum of the Phame v Paizes 1973 3 397 (A) within economic and legal principles to determine whether incorporeal things could possess characteristics of value or quality characteristics as in the case of corporeal things. The author uses practical economic examples to argue for the development of common law. The author identifies relevant Roman law principles which justify the legal nature of incorporeal things. It is demonstrated that the value of incorporeal things depends greatly on future circumstances. It is argued in this article that the courts’ willingness to extend the Aedilitian remedies and the wide interpretation of a dictum et promissum create an open door for any unsatisfied buyer with no entrepreneurial skills to claim a reduced price if the business is unable to achieve similar financial results to those prior to the conclusion of the contract. Currently the seller of a business has no clear or enforceable defense under these circumstances. The author subsequently suggests that relevant Roman law principles should be revisited in the aim to develop an appropriate defense for the seller.
Between Economic and Legal Analysis of Incorporated Things: a Critical "NO" to Aedilitian Remedies
CG Kilian
Potchefstroom Electronic Law Journal/Potchefstroomse Elektroniese Regsblad , 2006,
Abstract: This article analyses the dictum of the Phame v Paizes 1973 3 397 (A) within economic and legal principles to determine whether incorporeal things could possess characteristics of value or quality characteristics as in the case of corporeal things. The author uses practical economic examples to argue for the development of common law. The author identifies relevant Roman law principles which justify the legal nature of incorporeal things. It is demonstrated that the value of incorporeal things depends greatly on future circumstances. It is argued in this article that the courts’ willingness to extend the Aedilitian remedies and the wide interpretation of a dictum et promissum create an open door for any unsatisfied buyer with no entrepreneurial skills to claim a reduced price if the business is unable to achieve similar financial results to those prior to the conclusion of the contract. Currently the seller of a business has no clear or enforceable defense under these circumstances. The author subsequently suggests that relevant Roman law principles should be revisited in the aim to develop an appropriate defense for the seller.
Glimmering Utopias: 50 Years of African Film Flimmernde Utopien: 50 Jahre afrikanischer Film
Cassis Kilian
Africa Spectrum , 2010,
Abstract: The history of African film began in the 1960s with the independence of the colonies. Despite all kinds of political and economic difficulties, numerous films have been made since then, featuring wide-ranging processes of consolidation, differentiation and transformation which were characteristic of post-colonial sub-Saharan Africa. However, these feature films should not merely be viewed as back references to specifically African problems. The glimmering fictions are imagination spaces. They preserve ideas about how the post-colonial circumstances should be approached. Seen from this perspective, the history of African film may be studied as a history of African utopias. Die Geschichte des afrikanischen Films begann mit der Unabh ngigkeit in den 1960er Jahren. Seitdem sind trotz aller politischen und konomischen Probleme zahlreiche Filme entstanden. Sie geben umfassende Konsolidierungs-, Differenzierungs- und Transformationsprozesse wieder, die für das postkoloniale subsaharische Afrika charakteristisch waren. Die Spielfilme sollten allerdings nicht nur als Rückschau auf spezifische Probleme Afrikas interpretiert werden. Diese flimmernden Phantasien stellen Imaginationsr ume dar; in ihnen sind Ideen enthalten, wie den Bedingungen der postkolonialen Gesellschaften begegnet werden k nnte. Aus dieser Sicht heraus k nnte die Geschichte des afrikanischen Films auch als Geschichte afrikanischer Utopien erforscht werden.
Measuring Chiral Parameters in the Strongly Interacting W system at a Linear Collider
W. Kilian
Physics , 1996,
Abstract: In the absence of a Higgs particle vector boson scattering amplitudes are generally described by an electroweak chiral Lagrangian below the resonance region. For a Linear Collider with CMS energy $\sqrt{s}=1.6 TeV$ and an integrated luminosity of $200 fb^{-1}$ we estimate the sensitivity on the chiral parameters $\alpha_4$ and $\alpha_5$. We consider the processes $e^+e^-\to W^+W^-\bar\nu\nu$ and $e^+e^- \to ZZ\bar\nu\nu$, performing a complete calculation which includes all relevant Feynman diagrams at tree level, without relying on the Equivalence Theorem or the Effective $W$ Approximation. The dominant backgrounds and $W/Z$ misidentification probabilities are accounted for.
Renormalized Soft-Higgs Theorems
Wolfgang Kilian
Physics , 1995,
Abstract: The Higgs couplings to matter fields are proportional to their masses. Thus Higgs amplitudes can be obtained by differentiating amplitudes without Higgs with respect to masses. We show how this well-known statement can be extended to higher order when renormalization effects are taken into account. We establish the connection with the Callan-Symanzik and renormalization group equations and consider also pseudoscalar Higgs couplings to fermions. Furthermore, we address the case where the Higgs couples to a heavy particle that is integrated out from the low-energy effective Lagrangian. We derive effective interactions where mass logarithms are resummed by renormalization-group methods, and give expansions of the results up to next-to-leading order.
Electroweak Interactions: Summary
W. Kilian
Physics , 2000, DOI: 10.1063/1.1394369
Abstract: The session on precision studies of electroweak interactions is summarized. The contributions address the bilinear, trilinear, quartic as well as heavy-quark interactions of the electroweak gauge bosons. This makes up a picture of the physics of electroweak symmetry and symmetry breaking which can be investigated with the proposed design of e+e- Linear Colliders and detectors.
Bubbletons are not embedded
Martin Kilian
Mathematics , 2010,
Abstract: We discuss constant mean curvature bubbletons in Euclidean 3-space via dressing with simple factors, and prove that single bubbletons are not embedded.
Random walks in the quarter plane, discrete harmonic functions and conformal mappings
Kilian Raschel
Mathematics , 2013, DOI: 10.1016/j.spa.2014.04.013
Abstract: We propose a new approach for finding discrete harmonic functions in the quarter plane with Dirichlet conditions. It is based on solving functional equations that are satisfied by the generating functions of the values taken by the harmonic functions. As a first application of our results, we obtain a simple expression for the harmonic function that governs the asymptotic tail distribution of the first exit time for random walks from the quarter plane. As another corollary, we prove, in the zero drift case, the uniqueness of the discrete harmonic function.
Page 1 /374
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.