Aumelas V.,YLEC Consultants |
Lecoffre Y.,HYDEO France |
Maj G.,YLEC Consultants |
IOP Conference Series: Earth and Environmental Science | Year: 2016
Micro-bubbles injection has long been used in hydrodynamic facilities for the control of dissolved and free air. In some cavitation tunnels , very large quantities of microbubbles (billions per second) are injected for rapid degassing and, in smaller quantities (millions per second), for cavitation nuclei seeding. Micro-bubbles can also be used as tracers for optical measurements including visualization, LDV or PIV. For these applications, bubbles must be sufficiently small to faithfully follow the flow. Depending on the quality and spatial characteristics of the micro-bubbles seeding, several optical methods can be applied: simple visualization gives access to semi-quantitative information on the behaviour of flows; LASER velocimetry provides information on the mean velocity and other temporal local characteristics of the flow. This paper presents some new micro-bubbles seeding devices recently developed by YLEC Consultants. These devices have been designed to fulfill specific requirements related to integration into cavitation tunnels and permit optical velocimetry measurement techniques such as Particle Image Velocimetry (PIV). The LEGI cavitation tunnel is the first tunnel which has been equipped with these microbubbles seeding systems dedicated to optical velocimetry. This paper presents the final integration schemes selected for micro-bubbles seeding into LEGI tunnel and discuss about practical concerns related to the use of the injection system for optical velocimetry. © Published under licence by IOP Publishing Ltd.
Duvaleix-Treguer S.,French National Institute for Agricultural Research |
Duvaleix-Treguer S.,Agrocampus Ouest |
Hammoudi A.,French National Institute for Agricultural Research |
Rouached L.,LEGI |
Soler L.G.,French National Institute for Agricultural Research
European Review of Agricultural Economics | Year: 2012
The objective of this article is to gain a better understanding of firms' strategies towards nutritional tax policies and to assess their impacts from a public health point of view. We determine how new products that are nutritionally improved can successfully emerge in an asymmetrical context in which firms do not have the same strategic incentives to change the characteristics of their products. The results show that nutritional regulations may induce changes in the product quality choices by firms, but may also affect the competitive game. Under some conditions, the economic distortions are not compensated by increased health benefits. © 2012 Oxford University Press and Foundation for the European Review of Agricultural Economics 2012; all rights reserved. For permissions, please email journals.permissionsoup.com.
Soupremanien U.,LEGI |
Person S.L.,LEGI |
Favre-Marinet M.,LEGI |
Experimental Thermal and Fluid Science | Year: 2011
This article presents experiments conducted with two single rectangular mini-channels of same hydraulic diameter (1.4mm) and different aspect ratios for conditions of horizontal boiling flow. The Forane® 365 HX used was subcooled (ΔTsub=15°C) for all the boiling curves presented in the paper. Local heat transfer coefficients were measured for heat flux ranging from 25 to 62kWm-2 and mass flux from 200kgm-2s-1 to 400kgm-2s-1. The boiling flows were observed with two different cameras (depending on the flow velocity) through a visualization window. The flow patterns in the two channels were compared for similar conditions. The results show that the boiling heat transfer coefficient and the pressure drop values are different for the two single mini-channels. For low heat flux condition, the channel with lowest aspect ratio (H/W=0.143) has a higher heat transfer coefficient. On the other hand, for high heat flux condition, the opposite situation occurs, namely the heat transfer coefficient becomes higher for the channel with highest aspect ratio (H/W=0.43). This is probably due to the earlier onset of dryout in the channel with lowest aspect ratio. For the two cases of heating, the pressure drop for the two-phase flow remains lower for the channel with lowest aspect ratio. These results show that the aspect ratio plays a substantial role for boiling flows in rectangular channels. As for single-phase flows, the heat transfer characteristics are significantly influenced (even though the hydraulic diameter remains the same) by this parameter. © 2010 Elsevier Inc.
Shahbaz M.,COMSATS Institute of Information Technology |
Khraief N.,University of Sousse |
Khraief N.,University of Nice Sophia Antipolis |
Renewable and Sustainable Energy Reviews | Year: 2015
Abstract This paper investigates the causal relationship between road transportation energy consumption, fuel prices, transport sector value added and CO2 emissions in Tunisia for the period of 1980-2012. We apply the newly developed combined cointegration test proposed by Bayer, C, Hanck, C. Combining non-cointegration tests. J Time Ser Anal 2013; 34(1): 83-95 and the ARDL bounds testing approach to cointegration for establishing the existence of long-run relationship in presence of structural breaks. The direction of causality between these variables is determined via vector error correction model (VECM). Our empirical exercise reveals that cointegration is present. Energy consumption adds in CO2 emissions. Fuel prices decline CO2 emissions. Road infrastructure boosts CO2 emissions. Transport value-added also increases CO2 emissions. The causality analysis indicates the bidirectional casual relationship between energy consumption and CO2 emissions. Road infrastructure causes CO2 emissions and similar is true from opposite side in Granger sense. The bidirectional causality is also found between transport value-added and CO2 emissions. Fuel prices cause CO2 emissions, energy consumption, road infrastructure and transport value-added in Granger sense. This paper provides new insights to policy makers for designing a comprehensive energy, transport and environment policies for sustainable economic growth in long run. © 2015 Elsevier Ltd.