Showing papers by "Karlsruhe Institute of Technology published in 1979"
TL;DR: There have been well over two hundred experimental studies published on the turbulent wall jet as mentioned in this paper, of which about one half have been prompted by heat transfer considerations and in most of these cases the flow field has been insufficiently well documented to merit close attention for the present purpose.
282 citations
TL;DR: In this article, it was shown that the dynamic shear modulus in homogenous isotropic sand samples depends upon the direction of stress and not the first invariant of stress tensor.
Abstract: By special measurement technique it is shown that the dynamic shear modulus in homogenous isotropic sand samples depends upon the direction of stress. Furthermore it can be demonstrated that the shear modulus is not related to the first invariant of stress tensor as assumed hitherto, but to the respective stress component itself. Measurements were performed making use of the cross correlation method and stochastic shear wave excitation by a special shear wave exciter that avoids the generation of p waves. Polarized shear waves were generated in a cubical sand sample and the shear wave velocity was measured independent of the value and the direction of the stress in the sample. Due to the sensivity of the correlation method small vibration amplitudes could be applied, such that a linear stress-strain relation could be assumed. It was shown that the placing technique of the sand had no influence upon the test results.
251 citations
TL;DR: In this article, a self-consistent direct method (SCD) is proposed to treat equations which include complete CI(SD), CEPA, MP-PT (3rd order), and MBPT of Bartlett and Silver as special cases.
215 citations
TL;DR: In this paper, the authors describe the application of a finite-difference calculation procedure to the problem of simulating the three-dimensional, turbulent flow in a strongly curved, open, 180° bend with straight inlet and outlet reaches.
Abstract: The paper describes the application of a finite-difference calculation procedure to the problem of simulating the three-dimensional, turbulent flow in a strongly curved, open, 180° bend with straight inlet and outlet reaches. The configuration can be considered to represent an element of a model meander, and the work presented here forms an important stage in efforts to simulate the flow in successive reverse-curvature bends. No restrictions other than the absence of flow separation and hydraulic jumps are imposed. Full account is taken of non-linear fluid-inertia and of turbulent diffusion terms. Effects of turbulence are represented by an eddy viscosity related to two parameters— the turbulent kinetic energy k and its rate of dissipation ϵ\N— for which related differential transport equations are solved. Predictions are presented for the transverse surface slope and velocity field in a configuration experimentally examined by Rozovskii. Agreement between predictions and experimental data is judged to be satisfactory on all major flow phenomena.
190 citations
TL;DR: In this article, it was shown that the functions f(z)=αez are the only nonconstant entire (meromorphic) functions which share two (three) distinct finite values with their derivative.
Abstract: In this paper it is shown that the functions f(z)=αez are the only nonconstant entire (meromorphic) functions which share two (three) distinct finite values with their derivative.
162 citations
TL;DR: In this paper, a new model for the mechanism of continent-continent collision at the Eastern Carpathians is proposed, which tries to explain the isolated occurrence of the intermediate seismic zone in Vrancea, at the edge of a paleoseismic zone beneath the Carpathian mountains.
158 citations
TL;DR: In this paper, a detailed cross-section of the Caledonian orogenic belt of northern Britain has been presented, which provides clear evidence of lateral variations in lithospheric structure, comparable with the gross geological variations.
151 citations
139 citations
TL;DR: In this article, a phenomenological description and a quantum-mechanical theory of electron transport in the anomalous bulk photovoltaic effect (ABPVE) in ferroelectrics are presented.
Abstract: We present a phenomenological description and a quantum-mechanical theory of electron transport in the anomalous bulk photovoltaic effect (ABPVE) in ferroelectrics. Our theory is based on a quadratic response formalism which leads to an exact expression for the short-circuit photovoltaic current (SCPVC). This theory indicates the existence of an ABPVE even in a system of pure Bloch states. We demonstrate the capability of our theory by performing an explicit calculation of the SCPVC for a one-dimensional model of independent impurities. From these results we conclude that sign changes of the SCPVC, as observed in BaTi${\mathrm{O}}_{3}$, are either due to impurities which have a bound excited state, or to Bloch states with two or more overlapping valence or conduction bands. There is evidence for both mechanisms.
117 citations
TL;DR: A short discussion of the superspace formulation of supergravity is given and the Bianchi identities are derived in this article, where supergravity constraints are imposed and the identities are solved in terms of superfields and their covariant derivatives.
101 citations
TL;DR: In this article, the authors investigate the semileptonic decays of heavy quarks in the leading non-trivial order in quantum chromodynamics and find the lepton energy spectrum very stable with respect to gluon corrections.
Journal Article•
TL;DR: In this article, it was shown that the dynamic shear modulus in homogenous isotropic sand samples depends upon the direction of stress and not the first invariant of stress tensor.
Abstract: By special measurement technique it is shown that the dynamic shear modulus in homogenous isotropic sand samples depends upon the direction of stress. Furthermore it can be demonstrated that the shear modulus is not related to the first invariant of stress tensor as assumed hitherto, but to the respective stress component itself. Measurements were performed making use of the cross correlation method and stochastic shear wave excitation by a special shear wave exciter that avoids the generation of p waves. Polarized shear waves were generated in a cubical sand sample and the shear wave velocity was measured independent of the value and the direction of the stress in the sample. Due to the sensivity of the correlation method small vibration amplitudes could be applied, such that a linear stress-strain relation could be assumed. It was shown that the placing technique of the sand had no influence upon the test results.
TL;DR: In this paper, it was shown that the curvature can be expressed in terms of the torsion and its covariant derivatives, which is the fundamental geometric object in supergravity.
Abstract: The first Bianchi identities are used to show, that in extended supergravity the curvature can be expressed in terms of the torsion and its covariant derivatives. The second Bianchi identities are shown to hold on account of the first ones. Thus all expressions containing the curvature may be written in terms of the torsion, which is the fundamental geometric object in supergravity.
01 Jan 1979
TL;DR: In this paper, a two-equation k-means model was applied to the problem of 3D free jets issuing from rectangular orifices, and the results showed that the decay of axial velocity is well predicted.
Abstract: The paper presents an application of the two-equation k—є model to the problem of three-dimensional free jets issuing from rectangular orifices. The turbulence model has been modified so that plane and round jets may be predicted with the same empirical input. The continuity, momentum, and turbulence equations are solved using the finite difference procedure of Patankar and Spalding for three-dimensional parabolic flows and results are presented for aspect ratios of 1, 5, 10, and 20. The decay of axial velocity is well predicted. The behavior of the half-widths, however, is not well predicted when no lateral velocities are specified at the orifice; the measured crossover of jet major and minor axes is not obtained. The possible existence of a lateral velocity field at the orifice cross section is examined and its ability to produce the observed jet inversion is demonstrated. Profile shapes in the orifice short-axis direction are in good agreement with measurements, and, when inlet lateral velocities are specified, the long-axis profiles are also predicted fairly well. The measured “saddle-shape” of the profiles in this direction is, however, not obtained; this will require further changes to the turbulence model.
TL;DR: In this article, a mathematical model for the prediction of spreading and rising of submerged round buoyant jets discharged into a stratified, flowing ambient fluid is presented, based on the differential equations for the conservation of mass, momentum, concentration and thermal energy.
TL;DR: In this article, the authors used the strain relief technique to confirm principal stress directions, approximately equal to those obtained by fault plane solutions of earthquakes, and assumed that the observed state of stress is mainly caused by a sideways extension of the mountain body due to the effects of unloading and topography.
TL;DR: In this paper, a bifurcation analysis of a strain hardening dilatant sand sample in the triaxial test is carried out, and the analysis shows that the test yields only then the limiting soil properties if the sample is compact enough and confining pressure does not exceed a critical value depending on the soil anisotropy and the slenderness of the sample.
Abstract: A bifurcation analysis of a strain hardening dilatant sand sample in the triaxial test is carried out. The analysis shows that the triaxial test yields only then the limiting soil properties if 1) the sample is compact enough and 2) if the confining pressure does not exceed a critical value depending on the soil anisotropy and the slenderness of the sample.
TL;DR: Bacteriophage T3 and T7 protect their DNA from restriction by producing, as the earliest detectable phage functions, anti-restriction proteins, which inhibit E. coli K12 restriction endonuclease by direct interaction.
Abstract: Bacteriophage T3 and T7 protect their DNA from restriction by producing, as the earliest detectable phage functions, anti-restriction proteins Although the two phage proteins differ in their chromatographic and antigenic properties, they act by the same mechanism: the anti-restriction proteins inhibit E coli K12 restriction endonuclease by direct interaction
TL;DR: In this paper, an axial current is defined in supersymmetric QED and its anomalous Ward identity equations are derived, and the anomaly is shown to have no radiative corrections.
TL;DR: In this paper, the authors investigated the four-jet production processes e + e − → q q ¯ g g g and e+ e − √ q q¯ g g → q Q ¯ q q ¾ q ¼ in lowest order QCD perturbation theory, and they estimated that 4J events should be detectable at a rate of about 5% at the highest PETRA energy.
TL;DR: In this article, evidence for the forward production of D + mesons has been found in pp collisions at a c.m. energy of 52.5 GeV and a signal of 92 ± 18 events above background has been observed in the decay channel.
TL;DR: In this paper, available seismic refraction data from three different continental areas, northern Britain and the eastern and western United States, has been studied for possible Pn, velocity anisotropy using the methods described by Bamford.
Abstract: Summary. Available seismic refraction data from three different continental areas, northern Britain and the eastern and western United States, has been studied for possible Pn, velocity anisotropy using the methods described by Bamford. There are various deficiencies in the time—distance data used in each case but, while the uppermost mantle beneath northern Britain and the eastern United States seems to be isotropic within the limits of measurement error, there is a small but significant anisotropy beneath the western United States.
Both the amount (up to 3 per cent) and the direction (70–80° east of north) of this anisotropy are very similar to the results obtained in the Pacific Ocean off California. We tentatively conclude that this anisotropy is present as a consequence of the subduction of oceanic lithosphere beneath the western United States.
TL;DR: In this paper, velocity anisotropy of 15-29% was identified with directions of maximum and minimum velocities that can be broadly related to previously mapped orientations of joints.
Abstract: Seismic velocity anisotropy is predicted for cracked rocks containing either a naturally-occurring or an artificially-induced preferred orientation of cracks. Methods developed for the study of velocity anisotropy in the uppermost mantle have been applied to the in situ measurement of P-wave velocity anisotropy in fractured Carboniferous Limestone in Northwest England. At three different sites, first-arrival travel-time data has been obtained using conventional refraction equipment and a weight-drop source. Velocity anisotropy of 15–29% is identified with directions of maximum and minimum velocities that can be broadly related to previously mapped orientations of joints.
TL;DR: In this paper, a new economical finite-difference method is described for the calculation of three-dimensional heated surface jets discharging into stagnant water, where the equations solved are for continuity, lateral and longitudinal momentum, and thermal energy.
Abstract: A new economical finite-difference method is described for the calculation of three-dimensional heated surface jets discharging into stagnant water. The equations solved are for continuity, lateral and longitudinal momentum, and thermal energy. The turbulent shear stresses and heat fluxes in these equations are determined with a turbulence model involving simplified forms of the transport equations for these stresses and fluxes and the solution of differential transport equations for the turbulent kinetic energy κ and the rate of its dissipation e. The experimentally observed entrainment reduction due to buoyancy is reproduced by this model. The predictions are compared in detail with the recent measurements of Pande & Rajaratnam, which are judged to be superior to those of other investigators. The agreement is generally satisfactory.
TL;DR: In this paper, a long-range explosion seismic profiles on continents with penetration to a depth of about 100 km revealed both vertical and lateral variations of structure and physical properties in the sub-crustal lithosphere.
01 Jan 1979
TL;DR: Theoretical and experimental studies on a turbulent flow in a two-dimensional channel of aspect ratio 1:16 in which a square obstacle of half the channel height was located are reported in this paper.
Abstract: Theoretical and experimental studies are reported on a turbulent flow in a two-dimensional channel of aspect ratio 1:16 in which a square obstacle of half the channel height was located. A one dimensional laser-Doppler anemometer was used to measure the mean longitudinal velocity distribution and the rms values of the longitudinal velocity fluctuations. The measurements were carried out along the channel center from 20 channel heights upstream of the obstacle to 33 channel heights downstream. Flow visualization techniques were employed to observe the regions not covered by the LDA measurements. The governing partial differential equations were solved numerically, and results are described in the theoretical part of the paper. In the separated flow region, the Reynolds equations were solved using the two-equation k − ϵ turbulence model, and in the region downstream of the separation, the boundary-layer equations were solved with both k − ϵ and the three-equation \(k-\varepsilon -\bar{u}\bar{v}\) turbulence model. The calculations are compared with the measurements and demonstrate clearly that for turbulent flows with separation, the present state of turbulence modelling results in inaccurate predictions. Calculated values are presented for the increase in heat transfer rates and the pressure drop due to the obstruction.
TL;DR: Theoretical step structures for ideal homogeneous filaments based on the interactions implicit in the simple phase-slip-center model of Skocpol, Beasley, and Tinkham are shown explicitly in this article.
Abstract: Theoretical step structures for ideal homogeneous filaments based on the interactions implicit in the simple phase-slip-center model of Skocpol, Beasley, and Tinkham are displayed explicitly.
TL;DR: Tilapia mossambica were adapted from freshwater to 27% saltwater and from 35% salt-water to freshwater and during adaptation time, changes of plasma sodium, chloride, potassium and osmolality were followed.
TL;DR: In this article, the influence of shot peening on the bending fatigue strength of hardened specimens of a carbon steel is reported along with the evidence of scanning electron micrographs from fractured specimens.
Abstract: — The influence of shot peening on the bending fatigue strength of hardened specimens of a carbon steel is reported. Effects of residual compressive stresses after shot peening, as a function of distance from the surface, are discussed along with the evidence of scanning electron micrographs from fractured specimens. Subsurface crack initiation is reported at all stress amplitudes below a threshold value of 1100 N/mm2. Assuming that the fatigue strength is enhanced locally due to compressive residual stresses the experimental results can be explained with the aid of the Goodman relationship.