Outer layer turbulence intensities in smooth- and rough-wall boundary layers

Clear differences in turbulence intensity profiles in smooth, transitional and fully rough zero-pressure-gradient boundary layers are demonstrated, using the diagnostic plot introduced by Alfredsson, Segalini & Örlü (Phys. Fluids, vol. 23, 2011, p. 041702) – u?/U versus U/Ue, where u? and U are the local (root mean square) fluctuating and mean velocities and Ue is the free stream velocity. A wide range of published data are considered and all zero-pressure-gradient boundary layers yield outer flow u?/U values that are roughly linearly related to U/Ue, just as for smooth walls, but with a significantly higher slope which is completely independent of the roughness morphology. The difference in slope is due largely to the influence of the roughness parameter (?U+ in the usual notation) and all the data can be fitted empirically by using a modified form of the scaling, dependent only on ?U/Ue. The turbulence intensity, at a location in the outer layer where U/Ue is fixed, rises monotonically with increasing ?U/Ue which, however, remains of O(1) for all possible zero-pressure-gradient rough-wall boundary layers even at the highest Reynolds numbers. A measurement of intensity at a point in the outer region of the boundary layer can provide an indication of whether the surface is aerodynamically fully rough, without having to determine the surface stress or effective roughness height. Discussion of the implication for smooth/rough flow universality of differences in outer-layer mean velocity wake strength is include

Steric effects in adsorption of ions from mixed electrolytes into microporous carbon

With the goal to improve the capacitance in electrochemical double-layer capacitors (EDLCs) many studies on pore size/ion size relationship have been undertaken to achieve a better understanding of the charge storage mechanism in the electrochemical double-layer in confinement. A significant capacitance increase was achieved by using carbon electrodes with micropores (b1 nm), when the carbon pore size was close to the ion size. In this paper, the accessibility of narrow pores is investigated by selecting a carbon with a small pore size (b0.7 nm) and electrolyte mixtures with different ion sizes. It has been shown that the adsorption capacitance limitation observed for large cations and anions could be overcome by adding ions with a smaller effective size. This result demonstrates that the pores are accessible when their size matches the effective ion size and contradicts the surface saturation assumption; effective ion size which exceeds the pore size leads to current limitation. This work confirms that the steric effect is involved when ions are adsorbed into pores and highlights the importance of controlling ion size/pore size relationship for optimisation of the capacitive performance of EDLC devices

Electromagnetic Nondestructive Evaluation of Surface Decarburization on Steels : Feasibility and Possible Applications

The need of a nondestructive testing of surface decarburization on steels is very high, since, at the present time, only destructive methods (such as optical micrography, hardness tests or chemical analysis) are industrially used to cope with what turns out to be a particularly important problem on grades with high security requirements, due to a resulting lower fatigue strength

Studies of Flexible Barriers Under Debris Flow Impact: An Application to an Alpine Basin

AbstractThe aim of this paper is to analyze the most relevant aspects that influence the interaction between debris flow phenomena and protection barriers. The volume of the debris and its lithological nature are conditioning the barrier size and strength. This system is often complicated by environmental and climate influences that need to be taken into consideration as well; therefore, a correct design of a protection barrier system in an alpine basin is a complex procedure that needs to be rationalized. This paper will concentrate on the barrier dimension design proposing a rational scheme of study of the global problem. The application to an Alpine basin is reported

Lecoq Patrice, Nouveau regard sur Choqek’iraw (Choque Quirao) : un site inca au cœur de la cordillère de Vilcabamba au Pérou

Lancé en 2003, le programme de restauration et de valorisation du site inca de Choqek’iraw, fruit d’une coopération franco-péruvienne de grande envergure qui visait notamment à proposer une option touristique alternative à Macchu Picchu, site maltraité par l’afflux de centaines de milliers de visiteurs, trouve, avec ce volume, l’aboutissement de son volet strictement archéologique. Patrice Lecoq, responsable de l’équipe française, livre dans cet ouvrage, première monographie d’importance cons..

Alert threshold assessment based on equivalent displacements for the identification of potentially critical landslide events

Over the past years, the growing number of natural hazards all over the world has led to an increasing focus on activities aimed at studying and controlling the occurrence of these phenomena. In this context, monitoring systems have become a fundamental component for Landslide Early Warning Systems, allowing to understand the evolution of these processes and assess the need for dedicated mitigation measures. This result is achieved thanks to several technological advancements that led to the introduction of more accurate and reliable sensors, as well as automatic procedures for data acquisition and elaboration. However, despite these improvements, the data interpretation process is still a challenging task, in particular when it comes to the identification of critical events and failure forecasting operations. This paper presents a methodology developed to assess if a potentially critical event is displaying a significant deviation from previously sampled data, or if it could be classified as a false alarm. The process relies on the definition of a threshold value based on the landslide behavior preceding the event of interest. In particular, the reference value derives from the evaluation of equivalent displacements, defined as the displacements previously observed in a time interval equal to the one showed by the potentially critical event. This paper reports a series of examples referring to different case studies, involving both false alarms and real collapses, underlining the effectiveness of the proposed model as a useful tool to evaluate the landslide behavior with a near-real-time approach

Solvent effect on the ion adsorption from ionic liquid electrolyte into sub-nanometer carbon pores

This paper presents the results from the investigation of the influence of ion size on the capacitance behaviour of TiC-derived carbon (CDC) powders in the ethyl-methylimmidazolium-bis(trifluoromethane-sulfonyl)imide ionic liquid (EMI, TFSI) used as neat electrolyte at 60°C or as salt dissolved in acetonitrile and tested at room temperature. These studies were carried out with the assembly of conventional 3-electrode electrochemical cells as well as using the Cavity-MicroElectrode (CME) technique. The issues regarding the extents of desolvation of the electrolyte ions when adsorbed in the pores of the CDCs under applied potential were studied, the CME technique was found to be particularly efficient in the deduction of the effective ion size under solvated conditions