Dominant Bubble Research Articles

Three-dimensional multimode simulations of the ablative Rayleigh–Taylor instability

Multimode simulations of the evolution of the laser-driven, ablative Rayleigh–Taylor instability on planar, plastic targets are performed in three dimensions, with FAST3D–CM. The initial mass density target perturbations are random, with a power law dependence of k−2, a RMS surface finish of 0.1 μm, and perturbation wave numbers ranging from 2π/dmax to √2×(12π/dmax), for dmax=128 μm. At early nonlinear times, the perturbations grow to tile the target with approximately hexagonal bubbles that are of the shortest, initially seeded wavelengths not stabilized by density gradients. This tiling occurs on a time scale that is comparable to the eddy turnover time of the dominant bubble wavelength. When the target thickness is large compared to the dominant, short wavelengths, the bubbles continue to burn into the target and to evolve to progressively longer spatial scales. Predictions from second-order mode coupling and saturation models are found to be consistent with the simulation results.

Crystallography of rare galactic honeycomb structure near supernova 1987A

Near supernova 1987a, the rare honeycomb structure of 20–30 galactic bubbles measures 30 × 90 light years. Its remarkable regularity in bubble size suggests a single-event orgin which may correlate with the nearby supernova. To test the honeycomb's regularity in shape and size, the formalism of statistical crystallography is developed here for bubble sidedness. The standard size-shape relations (Lewis's law, Desch's law, and Aboav-Weaire's law) govern area, perimeter and nearest neighbor shapes. Taken together, they predict a highly non-equilibrium structure for the galactic honeycomb which evolves as a bimodal shape distribution without dominant bubble perimeter energy.

A generation‐dispersion model of ambient and transient bubbles in the close vicinity of breaking waves

Bubble models are necessary to ascertain bubble contribution to ocean‐atmosphere fluxes of gas, aerosols, humidity, and latent heat. Previous theories flatten the wave breaking layer to a theoretical boundary from which bubbles are dispersed by turbulence working against buoyancy lift. As a consequence, bubble population characteristics next to the surface are not derived from these models but depend on empirical or semiempirical assumptions made at this boundary. By considering bubble injection with puffs of intense turbulence, specifying how bubbles are first created by a small‐scale similarity reasoning, and using a wavy interface, the present bubble theory expands this layer to a more physical breaking layer. Bubble concentration density as a function of bubble diameter, depth, and sea state parameters is obtained through explicit integrals. The model is found to be consistent with the previous bubble theories: the back flattening of the model breaking layer indeed results in equations compatible with these theories. The model variations in bubble concentration density with different parameters is coherent with experimental laws: the dominant bubble concentration is found to vary as about d−4 with bubble diameter and u*3 with wind friction velocity, but because of breaking patches, a d−2 bubble distribution is obtained very close to the surface. The concordance of the model with experimental data in the recent and classic bubble literature is quite good.

BUBBLE FORMATION FROM ELASTIC HOLES

The elastic membrane sparger is studied by observing bubble formation at a single hole centered in a circular membrane. Two types of models are developed to forecast intrinsic properties of the elastic bubble generator: (i) flow rate as a function of pressure change (ii) bubble size as a function of flow rate. In the former, certain properties relating to the changing hole size are revealed, and in the second, the dominant bubble regime is delineated. Comparison of theory and experiment suggests the rubber sparger operates as a linear area device, that is, hole area appears to increase linearly with increasing pressure. This behavior has certain advantages over a fixed-hole sparger, for example the retardation of the onset of jetting. We next show certain modifications of the classical analysis can predict quite adequately the bubble sizes emanating from the flexible hole

The density and pressure of helium in bubbles in metals

Abstract The energy shift of the He 11S0−21P1 transition, ΔE(n), can be used to determine the density, n, of He in bubbles in metals. A self-consistent band structure calculation for solid fcc He yields a linear relationship ΔE=C.n with C th=22 × 10−3 eV nm3. Systematic electron energy loss spectroscopy and transmission electron microscopy studies of He bubbles in Al for various He doses and temperatures result in Cexp=(24±8).10−3 eV nm3 in agreement with theory. The analysis is consistent with the assumption that dislocation loop punching is the dominant bubble growth mechanism during high-dose room temperature implantation. The application to He bubbles in Ni indicates a maximum He density of n=0.2 × 103 nm−3 for which He should be solid at room temperature.