Improving the rheometry of rubberized bitumen: experimental and computation fluid dynamics studies

Multi-phase materials are common in several fields of engineering and rheological measurements are intensively adopted for their development and quality control. Unfortunately, due to the complexity of these materials, accurate measurements can be challenging. This is the case of bitumen-rubber blends used in civil engineering as binders for several applications such as asphalt concrete for road pavements but recently also for roofing membranes. These materials can be considered as heterogeneous blends of fluid and particles with different densities. Due to this nature the two components tends to separate and this phenomenon can be enhanced with inappropriate design and mixing. This is the reason behind the need of efficient dispersion and distribution during their manufacturing and it also explains while realtime viscosity measurements could provide misleading results. To overcome this problem, in a previous research effort, a Dual Helical Impeller (DHI) for a Brookfield viscometer was specifically designed, calibrated and manufactured. The DHI showed to provide a more stable trend of measurements and these were identified as being ‘‘more realistic” when compared with those obtained with standard concentric cylinder testing geometries, over a wide range of viscosities. However, a fundamental understanding of the reasons behind this improvement is lacking and this paper aims at filling these gaps. Hence, in this study a tailored experimental programme resembling the bitumen-rubber system together with a bespoke Computational Fluid Dynamics (CFD) model are used to provide insights into DHI applicability to perform viscosity measurements with multiphase fluids as well as to validate its empirical calibration procedure. A qualitative comparison between the laboratory results and CFD simulations proved encouraging and this was enhanced with quantitative estimations of the mixing efficiency of both systems. The results proved that CFD model is capable of simulating these systems and the obtained simulations gave insights into the flow fields created by the DHI. It is now clear that DHI uses its inner screw to create a vertical dragging of particles within a fluid of lower density, while the outer screw transports the suspended particles down. This induced flow helps keeping the test sample less heterogeneous and this in turns allows recording more stable viscosity measurements

Stratification d’un dépôt de sable formé par la houle. Essais en laboratoire

The stratification of a sand deposit formed by waves. The local structures of beach deposits are considered, and it is shown by scale model tests that unstable forms such as wave-generated sand ripples are preserved in the sedimentary structure of a beach deposit.Les études de mouvements de matériaux, sous l'effet de facteurs hydrauliques tels que courants et houles, ont principalement pour objet la détermination du transport solide et de ses effets sur la configuration des fonds. La structure interne des dépôts obtenus sur les modèles n'est pas examinée car sa connaissance n'offre pas d'intérêt pratique et de plus la différence de nature entre le matériau nature et le matériau modèle, dans la plupart des cas, lui enlèverait toute représentativité. Quelques essais de laboratoire ont montré comment s'organisaient les stratifications dans un dépôt de sable formé sous l'action d'un courant permanent. Une recherche analogue a été effectuée pour le cas de la houle. Il s'agit exclusivement d'une étude qualitative de laboratoire dont les résultats demanderaient confirmation, par des recherches sur le terrain, soit dans les sédiments actuels, soit dans des sédiments anciens dont les conditions de formation ont pu être établies avec certitude par d'autres moyens.Barailler Lucien. Stratification d’un dépôt de sable formé par la houle. Essais en laboratoire. In: Les instabilités en hydraulique et en mécanique des fluides. Compte rendu des huitièmes journées de l'hydraulique; Lille, 8-10 juin 1964. Tome 1, 1965

Évolution récente des modèles mathématiques d'agitation due à la houle. Calcul de la diffraction en profondeur non uniforme

The present paper describes a method used on a digital computer for calculating the effects of wave refraction and diffraction simultaneously at harbour sites. It is derived from the method used by Biesel and Ranson [3] in the case of uniform depth by consideration of the radiation of wave energy in water of gradually varying depth. The wave height and wavephase are given in complex forme ζ by formulae (1) and (2) where the Green function G2 (OM) is defined by (19) (20) and (21). For practical purposes the area is divided into theoretical basins of convex shape and the integral (2) is applied to the boundaries of these basins. The derivative normal to the boundary Γ is given by formulae (4) (5) and (6) and the derivative of the Green fonction is given by (22) (23) and (24). For calculation, the integrals (2) and (6) are given the form (8) (9) with an increment ΔSR chosen small enough with respect to the local wave length The coefficients RJK, SJK defined by (25) (26) are determined in the following manner : (i) The paths of a given number of wave rays, starting from the points Oi and Mk, where ζ and ∂ζ/∂n are to be found, are computed by means of formulae (28) to (31) inclusive; (ii) The auxiliary functions I, φ, β, σ, are computed at the points where the wave rays reach the bounndary Γ. Their values at the given points Mp Mg, are then derived by interpolation along Γ. At this step, the differential equation (33) is integrated with the initial conditions (36) for MK and (37) for Oi. This mathematical model was compared to laboratory scale models and proved to be satisfactory. Two examples are given here. (i) The wave pattern in the harbour illustrated in Figure 2 for a wave period of 10 sec. Owing to the narrowness of the breakwaters compared to the wave length, it was possible to consider them as thin walls in the mathematical model. The results given by both models as shown in Figure 3. (ii) The wave pattern just inside the harbour entrance illustrated in Figure 4. In a previous study by Montaz [7] the breakwaters were considered as thin walls and the mathematical model gave the results of Figures 5 and 7.2, which depart considerably from the results of Figures 5, 6 and 7.1 obtained with a physical model. An accurate reproduction of the sloping breakwater head on the mathematical model leads to the consistent results of Figures 6 and 7.3

Efforts sur une prise d'eau en mer comportant trois tours émergeantes. Essais en bassin à houle aléatoire

L'étude d'une prise d'eau de centrale nucléaire en mer tyrrhénienne, comportant une plate-forme et trois tours, a été effectuée sur un modèle réduit en houle aléatoire déferlant sur les fonds marins. On a reproduit des spectres de Pierson-Moskowitz et Jonswap et mesuré les efforts globaux et les pressions sur la structure, ainsi que les efforts de liaison entre les tours et la plate-forme. L'appareillage de mesure comportait des sondes capacitives, une balance à six composantes et des dards pour l'encastrement des tours dans la plate-forme, avec acquisition digitalisée et traitement informatisé. L'étude a permis d'apprécier la stabilité globale de l'ouvrage et le coefficient de sécurité

Etude anatomo-pathologique sur le coeur de chats et clinique des cardiopathies rencontrées

LYON1-BU Santé (693882101) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

Conception des digues à talus. Choix de l'amplitude à employer dans la formule d'Hudson

L'établissement des projets des digues à talus et dans une certaine mesure l'appréciation des résultats des essais sur modèle réduit font appel aux formules de stabilité établies à la suite de très nombreuses expériences de laboratoires. A une amplitude de projet est associé un critère de dommage. Les dommages subis récemment ont montré qu'il fallait dans certains cas changer de critère de stabilité et donc de coefficient dans les formules empiriques. En attendant un développement des moyens d'investigation, une réduction par un facteur de l'ordre de 2 du coefficient KD de la formule de Hudson conduit à un critère de stabilité acceptable pour le risque de rupture des blocs. Les essais d'études générales et particulières réalisés par Sogreah et les résultats publiés nous incitent à utiliser l'amplitude significative comme valeur caractéristique dans les formules de stabilité

Design and Modeling of Serial Data Transceiver Architecture by Employing Multi-Tone Single-Sideband Signaling Scheme

This paper presents the design and analysis of a serial link transceiver (TRX) architecture employing analog multi-tone (AMT) signaling for chip-to-chip communication. Multi-tone single-sideband (SSB) signaling scheme is proposed in TRX architecture in order to optimize bandwidth requirements for each sub-channel and to improve signal-to-noise ratio (SNR) by reducing inter-channel interferences (ICI) between neighbouring sub-channels. System-level modeling results show that the proposed TRX architecture enables equalizer-free communication at 16 Gb/s over a lossy backplane channel that exhibits 22 dB attenuation at 8 GHz, while conventional NRZ signaling TRX necessitates a two-stage continuous-time linear equalizer (CTLE). A channel frequency-response inversion scheme, the up/downconversion mechanism of the TX/RX data stream and the RX design considerations have been analyzed and investigated by architectural modeling