Primary Bubble Research Articles

Unsteady low Reynolds number shock boundary layer interactions

Finite element methods were used to perform an investigation of the interaction between a reflected shock wave and a low Reynolds number laminar boundary layer in Mach 2 flow. The finite element scheme makes use of the time-accurate flux-corrected transport technique and a fully unstructured mesh, which is adaptive to both viscous and gasdynamic effects. A boundary layer transformation was employed to eliminate both the upstream pressure gradient and resolution issues of the leading edge flow. Shock wave/boundary layer interactions were simulated for four different shock intersection Reynolds numbers: 600, 2400, 9600, and 24 000. While significant amounts of flow separation were found for all Reynolds numbers, the character and size of the separated region varied significantly. It was also noted that separation bubble lengths when normalized by the distance from the leading edge to the shock intersection point decreased as the Reynolds number increased for the conditions considered herein. However, the most interesting observation was the inherent unsteadiness found for the higher Reynolds numbers. This led to separation bubble instability and vortex shedding for the two highest Reynolds number cases. The results indicated a natural shedding frequency of 1.3 based on ambient velocity and primary separation bubble length for these two cases.

Pool boiling heat transfer—II. Thickness of liquid macrolayer formed beneath vapor masses

The macrolayer thickness was determined on the basis of the energy balance relation q CHF = δ 1 ϱ 1 H fg f, which was derived from the dryout model for liquids, proposed by Katto and co-workers. The critical heat flux (CHF) and the detachment frequency were measured on 20 mm diameter horizontal and vertical heated disks at pressures of 0.03–0.4 MPa with water, ethanol, methanol and acetone. Two semi-empirical correlations for the macrolayer thickness were derived by dimensional analysis of a model in which primary or coalesced bubbles form a macrolayer. The proposed correlations arrange the data of macrolayer thickness obtained from CHF measurements well.

Critical fluid-flow phenomenon in a gas-stirred ladle

Measurement of the velocities of bubbles and liquid with a two-element electroresistivity probe and laser-Doppler velocimeter, respectively, during bottom injection of air into a water bath, has confirmed the existence of a critical gas-injection rate. Above the critical flow rate, the change of axial bubble velocity in the air jet, and of liquid velocity with increasing volume flow rate, diminishes markedly. The existence of the critical flow rate is explicable from high-speed motion pictures of the vertical gas jets, which reveal four zones of gas dispersion axially distributed above the orifice: primary bubble at the orifice, free bubble, plume consisting of disintegrated bubbles, and spout at the bath surface. With increasing gas-injection rate, the free-bubble zone expands such that the point of bubble disintegration rises closer to the bath surface. Above the critical flow rate, the free bubbles rise with minimal breakup and erupt from the bath surface with maximum energy discharge. The combined Kelvin-Helmholtz, Rayleigh-Taylor instability theory has been applied to analyze the bubble breakup in the bath and the critical gas-injection rate in a gas-stirred ladle. The criterion for the critical diameter of bubble breakup has been found to depend primarily on the surface tension and density of the liquid. In the analysis, the propagation time of a disturbance on a bubble surface at the “most unstable” wave number has been compared with the bubble rising time in the bath in order to determine the critical gas-flow rate. The predicted critical values are in close agreement with the measured results.

A New Model for CHF in Pool Boiling at Higher Pressure.

The concept of critical heat flux (CHF) is discussed based on the mechanism that the CHF is caused by the dryout of a liquid layer formed on a heating surface. It is suggested that a liquid macrolayer is formed due to the coalescence of bubbles for most boiling systems, and that the dryout of the macrolayer is controlled by the hydrodynamic behavior of coalesced bubbles on the macrolayer. Based on these considerations, a new CHF model is proposed for saturated pool boiling at higher pressures. The idea of this model comes from a close examination of the measured diameters of various bubbles and the photographic records obtained by Semeria (1963) for water boiling under higher pressures. In the model, a liquid macrolayer is formed due to coalescence of the secondary bubbles formed from the primary bubbles. The detachment of the tertiary bubbles formed from the secondary bubbles determines the frequency of the liquid macrolayer formation. The CHF occurs when the macrolayer is dried out before the departure of the tertiary bubbles from the heating surface. One of the formulations of the model gives the well-known Kutateladze or Zuber correlation for CHF in saturated pool boiling.

A model for bubble formation from an orifice with liquid cross-flow

Potential flow theory is used to derive a theoretical model for gas bubble formation at an orifice exposed to liquid cross-flow in the plane wall of a duct. Model simulations show good correspondence with experimental data for single-bubble formation, consistent with primary bubble growth being controlled by liquid inertia forces. These forces are quantified in terms of radial velocity and acceleration of the gas—liquid interface, and relative velocity between bubble and liquid. A simple “bubble pressure minimum” criterion yields reasonable prediction of bubble size.

A model for the prediction of bubble size at a single orifice in two-phase gas—liquid systems

A new model for the prediction of volumes of bubbles generated from a single orifice in two-phase gas—liquid systems has been developed based on a rigorous bubble closure mechanism. The interaction between the primary bubble and subsequent bubbles formed at the orifice has been incorporated into the model at high gas flow rates. The distance traveled by the bubble from the orifice before it detaches is also calculated by the model. This has been validated by comparison with the available experimental data and it is found that this model represents an improvement over previous models.

Spacing is crucial for coordination of domain functions within the simian virus 40 core origin of replication.

The simian virus 40 core origin of replication is composed of distinct domains that are bracketed by DNA spacers. We created a matched set of insertion mutations in spacer sites to study the spatial relationships among origin domains. Insertions larger than a single base pair severely inhibit replication regardless of the helical phasing between domains. Replication-defective mutations reduce T-antigen binding and T-antigen-induced KMnO4 modifications of DNA to various extents. Mutations in the early half of the origin reduce T-antigen functions in the entire origin, whereas mutations in the late half reduce functions only in that half. Surprisingly, some mutations that severely inhibit DNA replication reduce T-antigen-induced melting and other structural changes within origin DNA to only a limited extent. In contrast, all replication-defective origin mutations prevent T antigen from extending the primary replication bubble beyond the limits of the core origin of replication. We conclude, therefore, that T-antigen-induced events within the core origin must be spatially coordinated for conversion of T-antigen hexamers bound to the core origin into mobile helicase units.

Magmatic gas source for the stratospheric SO2 cloud from the June 15,1991, eruption of Mount Pinatubo

Research Article| October 01, 1992 Magmatic gas source for the stratospheric SO2 cloud from the June 15,1991, eruption of Mount Pinatubo H. R. Westrich; H. R. Westrich 1Geochemistry Department 6118, Sandia National Laboratories, Albuquerque, New Mexico 87185 Search for other works by this author on: GSW Google Scholar T.M. Gerlach T.M. Gerlach 2U.S. Geological Survey, Cascades Volcano Observatory, 5400 MacArthur Boulevard, Vancouver, Washington 98661 Search for other works by this author on: GSW Google Scholar Author and Article Information H. R. Westrich 1Geochemistry Department 6118, Sandia National Laboratories, Albuquerque, New Mexico 87185 T.M. Gerlach 2U.S. Geological Survey, Cascades Volcano Observatory, 5400 MacArthur Boulevard, Vancouver, Washington 98661 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1992) 20 (10): 867–870. https://doi.org/10.1130/0091-7613(1992)020<0867:MGSFTS>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation H. R. Westrich, T.M. Gerlach; Magmatic gas source for the stratospheric SO2 cloud from the June 15,1991, eruption of Mount Pinatubo. Geology 1992;; 20 (10): 867–870. doi: https://doi.org/10.1130/0091-7613(1992)020<0867:MGSFTS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A water-rich magmatic gas phase escaped explosively from Mount Pinatubo on June 15, 1991, taking with it a load of crystalline and molten material sufficient to form pumice and tephra deposits with an estimated total dense-rock-equivalent volume of 3-5 km3 (Scott et al., 1991), and carrying in it enough sulfur to form a 20 Mt SO2 cloud in the stratosphere. Application of the "petrologic method" for estimating sulfur degassing during the climactic event from the sulfur content of trapped glass inclusions and matrix glasses in the pumice deposits requires an unacceptably large volume of erupted magma to account for SO2 in the stratospheric cloud. The ubiquitous presence of primary vapor bubbles in glass inclusions and unaltered anhydrite phenocrysts in the pumice suggest that sulfur was present in a separate H2O-rich gas phase of the Pinatubo magma before eruption. Thus, for this eruption, and perhaps others, the petrologic method for estimating sulfur degassing is prone to substantial underestimation of sulfur release and the potential climatic impact of past explosive eruptions. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Studies on Pool Boiling Heat Transfer. 4th Report. Thickness of Liquid Macrolayer Formed Beneath Vapour Masses.

Macrolayer thickness was determined on the basis of the relationship qCHF=δ1ρ1Hfgf, which was derived from the dry-out model of liquid film formed repeatedly on heated surfaces. Critical heat flux qCHF is measured on a horizontal heated disk of 20mm in diameter in the range of pressures from 0.02 MPa to 0.4 MPa for water and ethanol. Departure frequency of large coalesced bubbles, which entirely cover the heated disk, was calculated from the relationship f=0.215{g(ρ1-ρv)/ρ1}5/9/(ν1·D3)1/9. Theoretical relationships correlating the obtained data of macrolayer thickness are derived by the dimensional analysis, under the assumptions that a macrolayer is formed by the coalescence of primary bubbles or coalesced bubbles. The macrolayer data are well correlated with the derived correlations.

40Ar/ 39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres

Argon isotope data indicate retained argon in bulk amber (matrix gas) is radiogenic [ 40Ar/ 39Ar ≃32o] than the much more abundant surface absorbed argon [ 40Ar/ 39Ar ≃295.5]. Neutron-induced 39Ar is retained in amber during heating experiments to 150° -250°C, with no evidence of recoiled 39Ar found after irradiation. A maximum permissible volume diffusion coefficient of argon in amber (at ambient temperature) D≤1.5 x 10 −17 cm 2S −1 is calculated from 39Ar retention. 40Ar/ 39Ar age calculations indicate Dominican Republic amber is ≃ 45 Ma and North Dakota amber is ≃ 89 Ma, both at least reasonable ages for the amber based upon stratigraphic and paleontological constraints and upon the small amount of radiogenic 40Ar. To date, over 300 gas analyses of ambers and resins of Cretaceous to Recent age that are geographically distributed among fifteen noted world locations identify mixtures of gases in different sites within amber (Berner and Landis, 1988). The presence of multiple mixing trends between compositionally distinct end-members gases within the same sample and evidence for retained radiogenic argon within the amber argue persuasivley against rapid exchange by diffusion of amber-contained gases with moder air. Only gas in primary bubbles entrapped between successive flows of tree resin has been interpreted as original “ancient air”, which is an O 2-rich end-member gas with air-like N 2/Ar ratios. Gas analyses of these primary bubbles indicate atmospheric O 2 levels in the Late Cretaceous of ≃ 35%, and that atmospheric O 2 dropped by early Tertiary time to near a present atmospheric level of 21% O 2. A very low argon diffusion coefficient in amber persuasively argues for a gas in primary bubbles trapped in amber being ancient air (possibly modified only by O 2 reaction with amber).

40Ar/ 39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres

Argon isotope data indicate retained argon in bulk amber (matrix gas) is radiogenic [ 40Ar/ 39Ar ≃32o] than the much more abundant surface absorbed argon [ 40Ar/ 39Ar ≃295.5]. Neutron-induced 39Ar is retained in amber during heating experiments to 150° -250°C, with no evidence of recoiled 39Ar found after irradiation. A maximum permissible volume diffusion coefficient of argon in amber (at ambient temperature) D≤1.5 x 10 −17 cm 2S −1 is calculated from 39Ar retention. 40Ar/ 39Ar age calculations indicate Dominican Republic amber is ≃ 45 Ma and North Dakota amber is ≃ 89 Ma, both at least reasonable ages for the amber based upon stratigraphic and paleontological constraints and upon the small amount of radiogenic 40Ar. To date, over 300 gas analyses of ambers and resins of Cretaceous to Recent age that are geographically distributed among fifteen noted world locations identify mixtures of gases in different sites within amber (Berner and Landis, 1988). The presence of multiple mixing trends between compositionally distinct end-members gases within the same sample and evidence for retained radiogenic argon within the amber argue persuasivley against rapid exchange by diffusion of amber-contained gases with moder air. Only gas in primary bubbles entrapped between successive flows of tree resin has been interpreted as original “ancient air”, which is an O 2-rich end-member gas with air-like N 2/Ar ratios. Gas analyses of these primary bubbles indicate atmospheric O 2 levels in the Late Cretaceous of ≃ 35%, and that atmospheric O 2 dropped by early Tertiary time to near a present atmospheric level of 21% O 2. A very low argon diffusion coefficient in amber persuasively argues for a gas in primary bubbles trapped in amber being ancient air (possibly modified only by O 2 reaction with amber).

Characterization of a pilot plant airlift tower loop reactor: III. Evaluation of local properties of the dispersed gas phase during yeast cultivation and in model media

The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased.

Studies on pool boiling heat transfer. 1st. Report. Proposed physical model for kutateladze-zuber correlation of CHF.

The Kutateladze correlation (1948) is widely used to predict critical heat flux (CHF) for various geometries of heated surfaces. A reasonable model which gives the correlation is not yet known. In this paper, the physical implications of the correlation are discussed and a model giving the correlation has been proposed. This model is derived on the basis of the measured diameters of various bubbles and the photographic records of boiling in higher pressures by Semeria (1963). In the model, a macrolayer δ1 is formed by the coalescence of the secondary bubbles formed by the primary bubbles. Tertiary bubbles formed by the secondary bubbles determine the frequency f of the macrolayer formation. The CHF is determined by the following relation: qCHF=δ1ρlHfgf, where ρl is the density of liquid and Hfg is the latent heat of evaporation. One of the formulations of the model gives the Kutateladze or Zuber correlation.

MORB degassing: evolution of CO 2

With the gas pressure model for the occurrence of volcanic eruptions of Jaupart, Vergniolle and Tait and the 13C/ 12C Rayleigh fractionation model of Pineau and Javoy we can explain, using the results of our previous calculations on the nucleation and growth of bubbles in MORB, the observed quantities and isotopic ratios of carbon present in different forms in oceanic ridge tholeiites. The processes associated with the generation of MORB in the upper mantle produce a basaltic liquid which is saturated with CO 2. During the migration of this liquid to a magma chamber just below the ridge crest, nucleation of carbon dioxide bubbles takes place. In the magma chamber MORB loses many of these primary bubbles while it degasses. A second generation of bubbles is nucleated during eruption. Our model explains the presence of relatively large primary bubbles rich in CO 2 with a 13C/ 12C ratio comparable to that of diamonds or carbonatites. The secondary bubbles, which are smaller than the primary ones, also contain predominantly CO 2, but this CO 2 is relatively enriched in 12C and is not greatly different in isotopic composition from the carbon remaining in solution when MORB is emplaced on the ocean floor. Contamination carbon, always present, tends to be even more enriched in 12C.

A Unified Representation of Gas Dispersion in Upwardly Injected Submerged Gas Jets

The overall dispersion of gas injected vertically upward into a liquid has been studied. A generalised model has been proposed to delineate the different forms of gas dispersion in the liquid, between gas entry at the tuyere tip and exit at the bath surface. Four dispersion zones have been identified: primarybubble, free-bubble, plume and spout. The regimes have been characterised by means of a dispersion dimensionless group, N D, based on the injection Froude number and the reduced height of the dispersion, which varies with the axial gas fraction in the different regimes. Thus it has been shown that the primary bubbles only exist for values of N D lower than about 2.0 in both the air-water and helium-water systems. The free bubbles or zone of bubble disintegration in these systems occur in the range of ND between 2.0 and 4.5 while the plume extends from about N D = 4.5 to a higher value depending on the depth of the liquid phase. The transition to spout formation beyond the plume is marked by a sudden increase in gas fraction, at a level somewhat lower than the static height of the bath.

A Unified Representation of Gas Dispersion in Upwardly Injected Submerged Gas Jets

The overall dispersion of gas injected vertically upward into a liquid has been studied. A generalised model has been proposed to delineate the different forms of gas dispersion in the liquid, between gas entry at the tuyere tip and exit at the bath surface. Four dispersion zones have been identified: primarybubble, free-bubble, plume and spout. The regimes have been characterised by means of a dispersion dimensionless group, N D, based on the injection Froude number and the reduced height of the dispersion, which varies with the axial gas fraction in the different regimes. Thus it has been shown that the primary bubbles only exist for values of N D lower than about 2.0 in both the air-water and helium-water systems. The free bubbles or zone of bubble disintegration in these systems occur in the range of ND between 2.0 and 4.5 while the plume extends from about N D = 4.5 to a higher value depending on the depth of the liquid phase. The transition to spout formation beyond the plume is marked by a sudden increase in gas fraction, at a level somewhat lower than the static height of the bath.

Gas Bubbles in Fossil Amber as Possible Indicators of the Major Gas Composition of Ancient Air

Gases trapped in Miocene to Upper Cretaceous amber were released by gently crushing the amber under vacuum and were analyzed by quadrupole mass spectrometry. After discounting the possibility that the major gases N(2), O(2), and CO(2) underwent appreciable diffusion and diagenetic exchange with their surroundings or reaction with the amber, it has been concluded that in primary bubbles (gas released during initial breakage) these gases represent mainly original ancient air modified by the aerobic respiration of microorganisms. Values of N(2)/(CO(2) + O(2)) for each time period give consistent results despite varying O(2)/CO(2) ratios that presumably were due to varying degrees of respiration. This allows calculation of original oxygen concentrations, which, on the basis of these preliminary results, appear to have changed from greater than 30 percent O(2) during one part of the Late Cretaceous (between 75 and 95 million years ago) to 21 percent during the Eocene-Oligocene and for present-day samples, with possibly lower values during the Oligocene-Early Miocene. Variable O(2) levels over time in general confirm theoretical isotope-mass balance calculations and suggest that the atmosphere has evolved over Phanerozoic time.

Calculation of primary bubble volume in gravitational and centrifugal fields

AbstractA one‐stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces. In contrast to the two‐stage model, presented by Kumar and Kuloor, it was not assumed that the drag coefficient in bubble expansion can be described by the same constants as in the steady‐state bubble ascent. The constants were adapted in such a way that the introduction of an additional bubble volume was not necessary. It was demonstrated that this model describes the bubble formation in gravitational and centrifugal fields equally well and, furthermore, is also applicable to structurally viscous liquids, provided that the effective shear gradient is calculated from the equilibrium of shearing and buoyancy forces. The model is based on the assumption of a constant volumetric flow rate during bubble formation and, for this reason, a minimum Froude number is necessary in analogy to the weeping limit for sieve plates. The normalized presentation permits simple operation. The possibility of applying the model to drop formation was confirmed by comparison of experimental values with those, predicted by the model.

On the generation and growth of equatorial backscatter plumes: 2. Structuring of the west walls of upwellings

The west wall of large‐scale ‘upwellings’ that develop in the bottomside of the nighttime equatorial F layer becomes structured by the wind‐driven gradient drift instability, the same process that leads to the formation of striations in barium ion clouds. Upwellings are initiated by wavelike perturbations with long spatial wavelengths (∼400‐km) and are amplified by the collisional Rayleigh‐Taylor instability (and sometimes assisted by the gradient drift instability in the case of an upward moving F layer). The west wall structuring process is driven by an eastward neutral wind enhanced by reduced drag during the postsunset hours and a velocity shear in east‐west bulk plasma drift in the bottomside F layer. West wall structures evolve in a manner analogous to primary plasma bubbles, i.e., secondary plasma bubbles grow from the west wall. Their characteristics are compared with those of the primary bubbles and discussed in the light of existing theories.

Equatorial plasma bubbles: Vertically elongated wedges from the bottomside F layer

We address the question regarding the two‐dimensional shape of equatorial plasma bubbles in the plane transverse to the geomagnetic field. By comparing the east‐west spatial relationship of ion‐density depletions measured in‐situ by the Atmospheric Explorer E (AE‐E) satellite to backscatter plumes measured by the ALTAIR radar, we show that plasma bubbles are vertically elongated depletions that extend upward from the bottom side of the F layer, in the form of tilted wedges, rather than more isotropically shaped but isolated structures. The shape of plasma bubbles is inferred from (1) ion density depletions that exceeded 99% in the ‘neck’ regions of plumes and (2) the eastward drift velocities of the plumes. The expected electrodynamics of vertically elongated plasma bubbles are consistent with the observations of large eastward drift velocities of plumes that are comparable to F region plasma drift measurements made at Jicamarca and to F region neutral wind measurements made at Kwajalein. The results also reveal that the west wall of large‐scale altitude modulations of the bottomside F layer that produces the primary plumes and bubbles becomes structured, and evolves with the generation of secondary plumes and bubbles.