It seems likely that string theory has a landscape of vacua that includes very many metastable de Sitter spaces. However, as emphasized by Banks, Dine and Gorbatov, no current framework exists for examining these metastable vacua in string theory. In this paper we attempt to correct this situation by introducing an eternally inflating background in which the entire collection of accelerating co...

The continual and uninterrupted expansion of medical research funding is generally assumed to be a permanent feature of modern societies, but this expectation may turn out to be mistaken. Sciences tend to go through boom and bust phases. Twentieth century physics is an example where huge increases in funding followed an era of scientific breakthroughs. Speculative over-expansion led to diminish...

We have performed nonlinear ideal magnetohydrodynamic simulations of the long term evolution of a magnetized low-density “bubble” plasma formed by a radio galaxy in a stratified cluster medium. It is found that about 3.5% of the initial magnetic energy remains in the bubble after ∼ 8 × 10 years, and the initial magnetic bubble expansion is adiabatic. The bubble can survive for at least 8 × 10 y...

We formulate a general multiphase model representing water-bubble mixture fluid and multi-component bubble populations. An enhanced 2-DV VOF model with a k− turbulence closure is used to model the mixture fluid phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The initial bubbl...

The present study is performed to numerically analyze the growth of a vapor bubble during flow of water through a microchannel. The complete Navier– Stokes equations, along with continuity and energy equations, are solved using the SIMPLER (semi-implicit method for pressure-linked equations revised) method. The liquid–vapor interface is captured using the level set technique. The microchannel i...

High-speed images of bubbly flow coupled with simultaneous passive acoustic measurements were carried out in a bubble column staged with structured fibrous catalysts. Local observations made with a high-speed camera system allow a detailed understanding of the influence of fabric structure on bubble formation processes and the determination of the Sauter bubble diameter. With acoustic measureme...

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The efficiency of fluidized bed reactors depends on bubble distribution, bubble size and bubble velocity within the reactor. The sizes and size distributions of particles used in the bed may lead to different bubble behaviour. The objective of this work is to study the influence of particle size distribution on bubble behaviour. The results from the experiments will be used for validation of CF...

[1] The evolution of bubbles in a turbulent oceanic boundary layer is simulated using a multi-size multi-gas bubble model coupled with a Large Eddy Simulation model. Bubbles injected by breaking waves are brought into the boundary layer by episodic bubble plumes, and they form near-surface streaks in the convergence zone of Langmuir circulations. The equilibrium bubble distribution decays expon...

Many measurement schemes have been developed to study the resonant characteristics of a bubble near a surface. The desire is to be able to measure the free field characteristics of such a bubble. For experimental investigations, a trade-off must be made between the size of the apparatus and the free field measurement. Thus there is a need to study the effect of surface interference on the reson...