Solving the incompressible surface Navier-Stokes equation by surface finite elements

We consider a numerical approach for the incompressible surface Navier-Stokes equation on surfaces with arbitrary genus $g(\mathcal{S})$. The approach is based on a reformulation of the equation in Cartesian coordinates of the embedding $\mathbb{R}^3$, penalization of the normal component, a Chorin projection method and discretization in space by surface finite elements for each component. The approach thus requires only standard ingredients which most finite element implementations can offer. We compare computational results with discrete exterior calculus (DEC) simulations on a torus and demonstrate the interplay of the flow field with the topology by showing realizations of the Poincar\'e-Hopf theorem on $n$-tori

What Drives the Efficiency of Hard Coal Fuelled Electricity Generation? An Empirical Assessment

The efficiency of electricity generation in hard coal fired power plants varies considerably from country to country and over time. These differences occur both between developing and developed countries and between industrialised nations. The econometric analysis presented in this paper tests for the reasons of these discrepancies. In this examination abundance of hard coal and the price of hard coal are the two variables of our major interest. We assume that countries with an abundance of hard coal or relatively low costs of extraction show smaller degrees of efficiency than countries with poor deposits of this resource because the latter nations have a stronger dependency on efficient power plants than the former. Furthermore, higher prices should lead to more efficient electricity generation since production costs increase with growing hard coal prices. Our findings partially confirm these hypotheses and suggest that, among the chosen explanatory variables, hard coal abundance or the accessibility of hard coal, respectively, the hard coal price, the level of foreign direct investment inflows as well as the average power plant age are identified as principal drivers of power plant efficiency. From an environmental policy perspective we conclude that flexible policy instruments which internalise external effects caused by emissions as well as support for foreign investments are important means to foster energy efficiency. However, economic efficiency even if contrasting with energy efficiency must not be neglected in the design of energy policies. --energy efficiency,natural resources,hard coal fired power plant

A practical approach to offset permits in post Kyoto climate policy

International Carbon Offsets from developing countries and emerging economies such as permits from the Clean Development Mechanism (CDM) will potentially play an important role for cost containment in domestic greenhouse gas regulation schemes in industrialised countries. We analyse the potential role of offset permits assuming that major emitters such as the USA, Canada, Japan, Australia and New Zealand install domestic greenhouse gas regulation schemes to achieve the emissions reductions pledged in the Copenhagen Accord and seek cost containment. We estimate a potential demand for offset permits of 627 to 667 MtCO2e p.a. from industrialised countries. To describe the supply structure, we derive marginal abatement cost curves for developing countries and emerging economies. We find that developing countries and emerging economies can supply 627 to 667 MtCO2e p.a. at costs of approximately EUR 10 (in 2004 EUR), neglecting transaction costs and country specific risks. The highest potentials for the generation of carbon offsets are present in China, India and the rest of Asia. --emissions trading,offsets,CDM,marginal abatement costs,climate policy

Hydrodynamic interactions in polar liquid crystals on evolving surfaces

We consider the derivation and numerical solution of the flow of passive and active polar liquid crystals, whose molecular orientation is subjected to a tangential anchoring on an evolving curved surface. The underlying passive model is a simplified surface Ericksen-Leslie model, which is derived as a thin-film limit of the corresponding three-dimensional equations with appropriate boundary conditions. A finite element discretization is considered and the effect of hydrodynamics on the interplay of topology, geometric properties and defect dynamics is studied for this model on various stationary and evolving surfaces. Additionally, we consider an active model. We propose a surface formulation for an active polar viscous gel and exemplarily demonstrate the effect of the underlying curvature on the location of topological defects on a torus

Benjamin Ortmeyer: 100 Jahre Ernest Jouhy. Dialektische Vernunft als zweifelnde Ermutigung – zum Werk von Ernest Jouhy. Frankfurt a. M.: Protagoras Academicus, 2013. [Rezension]

Rezension von: Benjamin Ortmeyer: 100 Jahre Ernest Jouhy. Dialektische Vernunft als zweifelnde Ermutigung – Zum Werk von Ernest Jouhy. Frankfurt a. M.: Protagoras Academicus, 2013. 114 S. (ISBN 978-3-943059-12-0)

Diffuse interface models of locally inextensible vesicles in a viscous fluid

We present a new diffuse interface model for the dynamics of inextensible vesicles in a viscous fluid. A new feature of this work is the implementation of the local inextensibility condition in the diffuse interface context. Local inextensibility is enforced by using a local Lagrange multiplier, which provides the necessary tension force at the interface. To solve for the local Lagrange multiplier, we introduce a new equation whose solution essentially provides a harmonic extension of the local Lagrange multiplier off the interface while maintaining the local inextensibility constraint near the interface. To make the method more robust, we develop a local relaxation scheme that dynamically corrects local stretching/compression errors thereby preventing their accumulation. Asymptotic analysis is presented that shows that our new system converges to a relaxed version of the inextensible sharp interface model. This is also verified numerically. Although the model does not depend on dimension, we present numerical simulations only in 2D. To solve the 2D equations numerically, we develop an efficient algorithm combining an operator splitting approach with adaptive finite elements where the Navier-Stokes equations are implicitly coupled to the diffuse interface inextensibility equation. Numerical simulations of a single vesicle in a shear flow at different Reynolds numbers demonstrate that errors in enforcing local inextensibility may accumulate and lead to large differences in the dynamics in the tumbling regime and differences in the inclination angle of vesicles in the tank-treading regime. The local relaxation algorithm is shown to effectively prevent this accumulation by driving the system back to its equilibrium state when errors in local inextensibility arise.Comment: 25 page

What drives the efficiency of hard coal fuelled electricity generation? : an empirical assessment

The efficiency of electricity generation in hard coal fired power plants varies considerably from country to country and over time. These differences occur both between developing and developed countries and between industrialised nations. The econometric analysis presented in this paper tests for the reasons of these discrepancies. In this examination abundance of hard coal and the price of hard coal are the two variables of our major interest. We assume that countries with an abundance of hard coal or relatively low costs of extraction show smaller degrees of efficiency than countries with poor deposits of this resource because the latter nations have a stronger dependency on efficient power plants than the former. Furthermore, higher prices should lead to more efficient electricity generation since production costs increase with growing hard coal prices. Our findings partially confirm these hypotheses and suggest that, among the chosen explanatory variables, hard coal abundance or the accessibility of hard coal, respectively, the hard coal price, the level of foreign direct investment inflows as well as the average power plant age are identified as principal drivers of power plant efficiency. From an environmental policy perspective we conclude that flexible policy instruments which internalise external effects caused by emissions as well as support for foreign investments are important means to foster energy efficiency. However, economic efficiency - even if contrasting with energy efficiency - must not be neglected in the design of energy policies

Employment effects of regional climate policy: the case of renewable energy promotion by feed-in tariffs

For the case of the German state of Baden-Wuerttemberg, production and employment effects of the promotion of renewable energy sources are examined based on a regionalized input-output table. Our findings suggest that policy actions promoting renewable energy types do not necessarily create new jobs and additional turnover for the whole economy. They rather induce a structural change of the economy since other investments might be crowded out by investments in installations of renewable energy and the demand in other sectors might decrease. However, if the producers of the installations are able to export parts of their products to the rest of Germany and/or the rest of the world, these crowding out effects can be attenuated and turnover and employment effects might be positive for the state in total