A Reynolds Stress Closure for Compressible Turbulent Flow

Several studies of compressible flows show that the pressure-strain is the main indicator of the structural compressibility effects. Undoubtedly, this term controls the change in the Reynolds stress anisotropy. Regarding the model of Adumitroiae et al., the slow part of the pressure strain correlation like the Rotta model uses the standard coefficient C1. The model predictions do not show large differences when compressibility increases. Correction of this coefficient using the turbulent Mach number is proposed. The two forms model of Adumitroiae et al. (with and without correction of 1 C ) are considered to study compressible mixing layers . The obtained results show that the predictions of the proposed compressibility correction model agree with the experiment results of Goebel and Dutton

An Extension of the SSG Model on Compressible Turbulent Flow

This work focuses on the performance and validation of some recent Reynolds stress models in compressible homogeneous shear flow. The SSG model developed by Speziale Sarkar and Gatski has shown a great success in simulating a variety of incompressible complex turbulent flows. On the other hand, it has not predicted correctly the compressible turbulence at high speed shear flow. Thus, a compressibility correction for this model is the major aim of this study. In the present work, two recent compressible models for the pressure strain-strain correlation have been used to modify the linear term of the SSG model. These modifications make the linear term dependent on a turbulent Mach number. In addition, compressibility correction model for the slow part of the pressure strain is proposed. The obtained results are compared with DNS results of Sarkar. The results show that important parameters characteristic of compressibility in homogeneous turbulent shear flow are well captured by the extended SSG model

Evaluation Study of Pressure-Strain Correlation Models in Compressible Flow

This paper is devoted to the second-order closure for compressible turbulent flows with special attention paid to modeling the pressure-strain correlation appearing in the Reynolds stress equation. This term appears as the main one responsible for the changes of the turbulence structures that arise from structural compressibility effects. The structure of the gradient Mach number is similar to that of turbulence, therefore this parameter may be appropriate to study the changes in turbulence structures that arise from structural compressibility effects. Thus, the incompressible model (LRR) of the pressure-strain correlation and its corrected form by using the turbulent Mach number, fail to correctly evaluate the compressibility effects at high shear flow. An extension of the widely used incompressible model (LRR) on compressible homogeneous shear flow is the major aim of the present work. From this extension the standard coefficients Ci became a function of the compressibility parameters (the turbulent Mach number and the gradient Mach number). Application of the model on compressible homogeneous shear flow by considering various initial conditions shows reasonable agreement with the DNS results of Sarkar. The ability of the models to predict the equilibrium states for the flow in cases A1 and A4 from DNS results of Sarkar is examined, the results appear to be very encouraging. Thus, both parameters Mt and Mg should be used to model significant structural compressibility effects at high-speed shear flow

Evaluation of 1,4-Benzothiazines in Steel Corrosion Inhibition in 15% HCl: Experimental and Theoretical Perspectives

Corrosion inhibitors are essential for metal protection. In this study, the efficacy of 1,4-Benzothiazine derivatives, particularly ethyl 3-hydroxy-2-(p-tolyl)-3,4-dihydro-2H-benzo[b][1,4]thiazine-3-carboxylate (EHBT) and 2-(4-chlorophenyl)-1,4-benzothiazin-3-one (CBT), was examined for carbon steel corrosion inhibition in 15 wt.% HCl. Techniques such as Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), weight loss measurement, and Scanning Electron Microscopy assessed the inhibitors' performance. Results showed inhibitor efficiency increased with concentration, with CBT and EHBT achieving up to 97% and 98% effectiveness respectively. Both acted as mixed inhibitors, reducing anodic and cathodic reactions. Adsorption of these molecules onto the steel surface was consistent with the Langmuir isotherm model, suggesting physical and chemical interaction. SEM analysis confirmed the protective layer formation by 1,4-Benzothiazine derivatives. Additionally, Quantum Chemical Calculations and Molecular Dynamics simulations provided insights into their interaction mechanisms on the Fe(110) surface. This research highlights the potential of 1,4-Benzothiazine derivatives in corrosion protection and paves the way for their further development

Les lymphomes de l’anneau de Waldeyer traitement et pronostic

Les lymphomes non Hodgkiniens (LNH) qui prennent naissance au niveau de l’anneau de Waldeyer constituent une entité bien particulière tant sur le plan clinique, thérapeutique que pronostique. Les auteurs rapportent une étude rétrospective de 44 observations de LNH de l’anneau de Waldeyer colligées entre 1995 et 2002. Une chimiothérapie exclusive aété indiquée chez 80,6% des malades et une association chimio-radiothérapie a été réalisée chez 19,4%. Le taux de survie globale était de 42% à 5 ans. Dans notre étude quatre facteurs de mauvais pronostic ont été individualisés : un âge ≥ à 40 ans, les stades d’Ann Arbor II, III et IV, un taux de LDH ≥ 1,5 fois la normale et la survenue de rechute.Mots-clés : Lymphome, anneau de Waldeyer, chimiothérapie, radiothérapie, pronosti