Search results for " bubble"

Multiplicity of Radial Ground States for the Scalar Curvature Equation Without Reciprocal Symmetry

2022

AbstractWe study existence and multiplicity of positive ground states for the scalar curvature equation $$\begin{aligned} \varDelta u+ K(|x|)\, u^{\frac{n+2}{n-2}}=0, \quad x\in {{\mathbb {R}}}^n\,, \quad n>2, \end{aligned}$$ Δ u + K ( | x | ) u n + 2 n - 2 = 0 , x ∈ R n , n > 2 , when the function $$K:{{\mathbb {R}}}^+\rightarrow {{\mathbb {R}}}^+$$ K : R + → R + is bounded above and below by two positive constants, i.e. $$0<\underline{K} \le K(r) \le \overline{K}$$ 0 < K ̲ ≤ K ( r ) ≤ K ¯ for every $$r > 0$$ r > 0 , it is decreasing in $$(0,{{{\mathcal {R}}}})$$ ( 0 , R ) and increasing in $$({{{\mathcal {R}}}},+\infty )$$ ( R , + ∞ ) for a certain $${{{\mathcal {R}}}}&g…

Comparison between adaptive and uniform discontinuous Galerkin simulations in dry 2D bubble experiments

2013

Accepted by the Journal of Computational Physics Adaptive mesh refinement generally aims to increase computational efficiency without compromising the accuracy of the numerical solution. However it is an open question in which regions the spatial resolution can actually be coarsened without affecting the accuracy of the result. This question is investigated for a specific example of dry atmospheric convection, namely the simulation of warm air bubbles. For this purpose a novel numerical model is developed that is tailored towards this specific application. The compressible Euler equations are solved with a Discontinuous Galerkin method. Time integration is done with an IMEXmethod and the dy…

Shapes of a gas bubble rising in the vertical Hele–Shaw cell with magnetic liquid

2005

Abstract Dynamics of the bubble rising in the vertical Hele–Shaw cell with magnetic liquid in the normal magnetic field is studied. Linear stability analysis of the circular shape is carried out. Development of the instability with respect to the lowest symmetric mode is simulated by the boundary integral equation technique.

An experimental study of the antineutron-light nucleus annihilation at 1.4 GeV/c

1979

The heavy liquid bubble chamber, Gargamelle, has been used to investigate the gross features of the annihilation of antineutrons in light nuclei (mainly Carbon). Results are presented on the distributions of multiplicity, momentum and emission angle for charged pions and protons together with a simple model to describe them.

Analysis of joining and division of gas bubbles based on measurements of their motion trajectories

2014

The paper presents considerations on motion of a group of air bubbles. Special attention has been paid to interactions between them. The author presents the test stand structure and the idea of image tomograph used for measurements of bubble motion trajectories. The results of measurements have been presented in a three-dimensional space, and next characteristic behaviours of the moving bubbles were analyzed. Some basic mechanisms of the gas bubble division have been classified. DOI: http://dx.doi.org/10.5755/j01.mech.20.1.6596

ADVANCED STATISTICAL ANALYSIS OF LOCAL BUBBLE SIZE DISTRIBUTIONS IN 2D GAS FLUIDIZED BEDS

2009

The principal difficulty in analysing fluidization quality and bubble dynamics is related to the possibility of measuring or predicting the physical and geometrical properties of gas bubbles rising in a granular medium. Even the development of detailed experimental correlations gives poor results, being necessary a fully statistical approach. On the above basis, the present work focuses on the statistical analysis of the behaviour of a 2-D fluidized bed operating under bubbling and slugging conditions, performing measurements of Local Bubble Size Distributions (BSD) along the bed. The analysis allowed to observe a characteristic bimodal shape of BSDs for different particles dimension and fl…

Mode-particle Interactions as Sources of Gamma-ray Bubbles in the Galaxy

A plasma outflow coming from the center of Our Galaxy is simulated by an ion beam reaching a nearly stationary magnetic field that can excite lower hybrid waves efficiently in the rarefied plasma (10-2-10-4 cm-3) surrounding the whole galaxy. The electrostatic lower hybrid waves are driven to instability via Cerenkov interaction. In this work we derive (by using a fluid model) the relevant dispersion relation and the expression for the growth rate by solving the dispersion relation both analytically and numerically. Parametric studies show that the growth rate of the instability increases with the beam density. The instability is found to have the maximum growth rate when the perpendicular …

(Un)Sustainable Territories: Causes of the Speculative Bubble in Spain (1996–2010) and its Territorial, Environmental, and Sociopolitical Consequences

2012

In this paper we analyse the causes of the Spanish property model and its territorial, social, and political consequences. Particular attention is paid to sociopolitical contexts. These consequences include excessive dependence on economic activity and employment in the housing construction sector, the irreversible disappearance of landmarks in the country’s collective history and culture, and examples of ‘policy capture’, especially at local and regional levels. This lengthy process has led to corruption in town planning and an increase in poor policy decisions, greatly harming Spain’s reputation. Keywords: urban sprawl, speculative property bubble, unbalanced growth, recession, corruption…

Local gas-liquid hold-up and interfacial area via light sheet and image analysis

2010

Particle Image Velocimetry techniques coupled with advanced Image Processing tools are receiving an increasing interest for measuring flow quantities and local bubble-size distributions in gas-liquid contactors. In this work, an effective experimental technique for measuring local gas hold-up and interfacial area, as well as bubble size distribution, is discussed. The technique, hereafter referred to as Laser Induced Fluorescence with Shadow Analysis for Bubble Sizing (LIF-SABS) is based on laser sheet illumination of the gas-liquid dispersion and synchronized camera, i.e. on equipment typically available within PIV set-ups. The liquid phase is made fluorescent by a suitable dye, and an opt…

A NOVEL TECHNIQUE FOR MEASURING LOCAL BUBBLE SIZE DISTRIBUTION

2009

A novel experimental technique for measuring the local gas hold-up and the statistical distribution of local bubble size, is proposed. The technique is based on laser sheet illumination of the gas-liquid dispersion and synchronized camera, i.e. on equipment typically available in PIV set-ups. The liquid phase is made fluorescent by a suitable dye, and a band-pass optical filter is placed in front of the camera optics, in order to allow only fluoresced light to reach the camera CCD. In this way bubbles intercepted by the laser sheet are clearly identified thanks to the neat shade resulting in the images. This allows excluding from subsequent analysis all bubbles visible in the images but not…