Experience Gained Using Second-Moment Closure Modeling for Transitional Flows Due to Boundary Layer Separation

This paper presents detailed information on the experience gained during the attempts to model a set of transitional flows due to boundary layer separation. These flows are developed on a flat plate with a semi-circular leading edge and they have been coded by the ERCOFTAC Special Interest Group on Transition, as T3L flows. Different freestream velocities and turbulence intensities configure these transitional flows and, by consequence, govern the transition mechanism, resulting in larger or smaller transitional regions. The modeling of the T3L flows has been performed by adopting a low-Reynolds number second-moment closure turbulence model. The results showed satisfactory agreement with the experimental measurements, although some difficulties regarding successful convergence have been faced. The final conclusion is that turbulence modeling can present quite accurate results for transitional flows without any additional use of ad-hoc modifications or additional equations based on various transition models and intermittency transport modeling.     

169Tm Mössbaüer spectroscopy and crystal field calculations in TmNi3 and TmCo3 intermetallics

The values of the magnetic moments and the electric field gradient in TmNi₃ and TmCo₃ are obtained from ¹⁶⁹Tm Mössbauer spectroscopy. These values are compared to those from crystal field model based on point charge calculations for these intermetallics.     

Separation-induced boundary layer transition: Modeling with a non-linear eddy-viscosity model coupled with the laminar kinetic energy equation

We present an effort to model the separation-induced transition on a flat plate with a semi-circular leading edge, using a cubic non-linear eddy-viscosity model combined with the laminar kinetic energy. A non-linear model, compared to a linear one, has the advantage to resolve the anisotropic behavior of the Reynolds-stresses in the near-wall region and it provides a more accurate expression for the generation of turbulence in the transport equation of the turbulence kinetic energy. Although in its original formulation the model is not able to accurately predict the separation-induced transition, the inclusion of the laminar kinetic energy increases its accuracy. The adoption of the laminar kinetic energy by the non-linear model is presented in detail, together with some additional modifications required for the adaption of the laminar kinetic energy into the basic concepts of the non-linear eddy-viscosity model. The computational results using the proposed combined model are shown together with the ones obtained using an isotropic linear eddy-viscosity model, which adopts also the laminar kinetic energy concept and in comparison with the existing experimental data.     

Magnetic properties of the equiatomic ternary RTSn compounds (R = rare earth, T = Pt, Rh)

Magnetic susceptibility studies on the hexagonal ternary equiatomic RTSn (R = rare earth and Y; T = Pt, Rh) compounds have been realized. These compounds are isostructural to Fe₂P with space group P 2m. The ordering temperatures of all compounds are smaller than 19 K. The susceptibility of YTSn is temperature independent.     

Structure magnetique des composes intermetalliques terre rare-nickel de formule TNi3

We have studied by neutron diffraction the intermetallic compounds TNi₃ (T = Pr, Nd, Tb, Dy, Tm). ^At 4.2K the PrNi₃ and TmNi₃ compounds are ferromagnetic with easy magnetisation axis parallel to C. The structures of the NdNi₃, TbNi₃, DyNi₃ compounds are canted. The magnetic moments of the nickel atoms are almost zero.     

Neutronenbeugungsuntersuchungen der magnetischen Struktur von TmCo3

The magnetic structure of the intermetallic TmCo₃ compound, determined by neutron diffraction measurements at 4.2 K on a powder sample, is colinear to the hexagonal c-axis, with the magnetic moments of Tm- and Co-ions being antiparallel coupled. The saturation moments have been found to beµ(Tm)=6.5µ _B andµ(Co)=0.8µ _B . The calculated magnetic moment of the Tm-ion by crystal field theory, based on a point charge model, is that of the free Tm³⁺ ion.     

The magnetic structure of HoCo2Si2

We have carried out neutron diffraction on a HoCo₂Si₂ powder sample at 4.2 K. The magnetic structure of this compound is collinear antiferromagnetic with the holmium magnetic moments parallel to the c-axis of the crystal. The magnetic moment value of holmium is 9.85 μ_B. The magnetic space group is I4/mm'm' (Sh⁴¹⁰₁₂₈) k = 000 The ordering temperature is t_n = 12(1) K.     

Magnetismus in den intermetallischen SEAu3-Verbindungen (SE=Gd,Tb, Dy,Ho, Er und Tm)

The relation between inner displacement and strain is established and simplified by group theory. Results are given for the diamond structure (C, Ge, Si), cobalt (Co), graphite (C), neodymium (Nd), spinel (MgAl₂O₄). For these crystals we get an enormous reduction of the number of parameters to be determined by measurement.     

Neutron diffraction study of DyCu2Ge2

The DyCu₂Ge₂ compound was studied by neutron diffraction on the Grenoble Nuclear Research Center multicounter system. The compound is isostructural to the rare earth RCu₂Ge₂ compounds with space group I4/mmm. 19 superlattice lines were observed in the 3 K pattern which are consistent with a doubling of the unit cell in the a and c directions. The moment value is 8 μ_B making an angle of 30° with a and 70° with c axis. The structure consists of ferromagnetic (1 0 1) layers with antiferromagnetic coupling between them. The Néel and Curie paramagnetic temperature of this compound is 8 K and ? 15 K respectively.     

A powder neutron diffraction study of the ErCu2Ge2 compound - crystal field

The compound ErCu₂Ge₂ was studied by neutron diffraction. The diffraction diagram of this compound at 170 K agrees with its crystallographic structure. Its diagram at 1.9 K reveals the existence of superlattice lines consistent with a cell doubled in the a and c directions. The erbium magnetic moment (8.0±0.4)μ_B lies on the c-axis. Crystal field calculations on the Er³⁺ site give 7.9μ_B, with easy magnetization axis the c-axis of the crystal. Copper must contribute to the V^m_l crystal field parameters with a charge equal to 0.6⁺.