Search results

The purpose of this paper is to study a gas bubble flowing in a micro-channel filled with liquid and to quantify the compressibility effects induced in the bubble by a heat supply at the walls of the channel.

The paper presents a model and its numerical implementation. A hybrid method combining front-tracking techniques and a Heaviside step function is introduced to ensure an accurate satisfaction of the mass and energy conservation laws.

Compressibility effects in the bubble are quantified. Test cases for numerical simulations of two-phase flows involving heat transfer are proposed.

The authors present original test cases in which expansion or compression of a gas bubble flowing in a liquid are induced by heat transfer at the wall.

External natural convection is rarely studied by numerical simulation in the literature due to the fact that flow of interest takes place in an unbounded domain and that if a limited computational domain is used the corresponding outer boundary conditions are unknown. In this study, we propose outer boundary conditions for a limited computational domain and make the corresponding numerical implementation in the scope of a projection method combining spectral methods and domain decomposition techniques. Numerical simulations are performed for both steady natural convection about an isothermal cylinder and transient natural convection around a line‐source. An experiment is also realized in water using particle image velocimetry and thermocouples to make a comparison during transients of external natural convection around a platinum wire heated by Joule effect. Good agreement, observed between numerical simulations and experiments, validated the outer boundary conditions proposed and their numerical implementation. It is also shown that, if one tolerates prediction error, numerical results obtained remain at least reasonable in a region near the line‐source during the entire transients. We thus paved the way for numerical simulation of external natural convection although further studies remain to be done for higher heating power (higher Rayleigh number).

This chapter focuses on diversity issues in France. It shows how these issues came historically in the French context and how the main tensions generated, notably the equality-diversity and universality-diversity tensions, are not understandable without a knowledge of the French Republicanism which gives to the foundations of the French social fabric its peculiarities.

The US fossil fuel industry is vulnerable to opposition from other sectors of the ruling class. Non-fossil fuel capitalists might conclude that climate breakdown jeopardizes their interests. State actors such as judges, regulators, and politicians may come to the same conclusion. However, these other elite actors are unlikely to take concerted collective action against fossil fuels in the absence of growing disruption by grassroots activists. Drawing from the history of the Obama, Trump, and Biden presidencies, I analyze the forces determining government climate policies and private-sector investments. I focus on how the climate and Indigenous movements have begun to force changes in the behavior of certain ruling-class interests. Of particular importance is these movements' progress in two areas: eroding the financial sector's willingness to fund and insure fossil fuels, and influencing judges and regulators to take actions that further undermine investors' confidence in fossil fuels. Our future hinges largely on whether the movements can build on these victories while expanding their base within labor unions and other strategically positioned sectors.

Air travel is becoming increasingly recognized as a source of greenhouse gas emissions contributing to climate change. This is particularly relevant for the university sector, which relies heavily on staff air travel for domestic and international mobility.

Using a qualitative content and textual analysis of Australian university sustainability policies, documents and Web pages, this paper discusses the extent to which these organizations take the task of reducing emissions from flying seriously.

Universities fall into one of three groups in this regard. “Air Travel Ignorers” are organizations that either have no sustainability policy or none that recognize air travel as a source of greenhouse gas emissions. The second group – “Recognition without Intervention” – describes universities that do acknowledge the role of air travel in their carbon footprint, but do not propose any means to reduce the amount of flying they do. Third, “Air Travel Substituters” seek to substitute their air travel with a digital form of mobility, usually video conferencing.

The authors then highlight the need to decrease and denormalize university air travel through shifting shared expectations of mobility for events such as conferences and meetings.

By way of a conclusion, the authors discuss the nature of air travel for Australian academia and the relationship between various forms of mobility, connectedness and co-presence.

This is the first comprehensive analysis of Australian university sustainability policies with respect to air travel.

In our earlier papers we have presented a general algorithm for the solution of both compressible and incompressible Navier‐Stokes equations. The objective of the present work is to show the performance of this algorithm when it is used to solve thermal flow problems. Both natural and forced convection and transient problems are considered in this study. The semi‐implicit form of the algorithm has been used to deal with a variety of these problems.