Strategic issues in global climate change policy *

An analysis of prospects for deriving self-enforcing, global, greenhouse gas emission mitigation agreements is provided. Policy spillovers and carbon leakages are accounted for. Situations where mitigation effort should be concentrated in particular countries and where efficient outcomes can be fostered by international trade in emissions permits are discussed. The use of auxiliary policies to transform intractable Prisoner's Dilemma incentive problems to more tractable problems, the role of policy commitments and the strategic implications of 'no regret' and 'adaptation' policies are analysed. Dynamic and repeated game formulations are outlined. Copyright 2010 The Author. Journal compilation 2010 Australian Agricultural and Resource Economics Society Inc. and Blackwell Publishing Asia Pty Ltd.

Two-phase numerical study of the flow field formed in water pump sump: influence of air entrainment

In a pump sump it is imperative that the amount of non-homogenous flow and entrained air be kept to a minimum. Free air-core vortex occurring at a water-intake pipe is an important problem encountered in hydraulic engineering. These vortices reduce pump performances, may have large effects on the operating conditions and lead to increase plant operating costs.This work is an extended study starting from 2006 in LML and published by ISSA and al. in 2008, 2009 and 2010. Several cases of sump configuration have been numerically investigated using two specific commercial codes and based on the initial geometry proposed by Constantinescu and Patel. Fluent and Star CCM+ codes are used in the previous studies. The results, obtained with a structured mesh, were strongly dependant on main geometrical sump configuration such as the suction pipe position, the submergence of the suction pipe on one hand and the turbulence model on the other hand. Part of the results showed a good agreement with experimental investigations already published. Experiments, conducted in order to select best positions of the suction pipe of a water-intake sump, gave qualitative results concerning flow disturbances in the pump-intake related to sump geometries and position of the pump intake. The purpose of this paper is to reproduce the flow pattern of experiments and to confirm the geometrical parameter that influences the flow structure in such a pump. The numerical model solves the Reynolds averaged Navier-Stokes (RANS) equations and VOF multiphase model. STAR CCM+ with an adapted mesh configuration using hexahedral mesh with prism layer near walls was used. Attempts have been made to calculate two phase unsteady flow for stronger mass flow rates and stronger submergence with low water level in order to be able to capture air entrainment. The results allow the knowledge of some limits of numerical models, of mass flow rates and of submergences for air entrainment. In the validation of this numerical model, emphasis was placed on the prediction of the number, location, size and strength of the various types of vortices coming from the free surface. Contours of vorticity at free surface, air cores, isoline of pressure surface were particularly examined for some cases. Streamlines issued from the free surface and the volume of fraction of air allows visualizing the air entrainment