Mass Sink Research Articles

Immersed boundary computations of shear- and buoyancy-driven flows in complex enclosures

Cartesian grids used with the immersed boundary method (IBM) offer an attractive alternative for simulating fluid flows in complex geometries. We present a ghost fluid method for incompressible flows solved with staggered grids. The primary feature is the satisfaction of local mass continuity for ghost pressure cells, rather than extrapolating the pressures from within the flow domain. The method preserves local continuity in each cell and also global continuity. As a result, no explicit mass sources or sinks are needed. We have applied the method to study shear- and buoyancy-driven flows in a number of complex cavities.

Simulations of TOSQAN containment spray tests with combined Eulerian CFD and droplet-tracking modelling

The spray experiments TOSQAN 113 and TOSQAN 101, which were performed in the TOSQAN facility (located at the Institut de Radioprotection et de Sûreté Nucléaire, France), were simulated with the computational fluid dynamics (CFD) code CFX4.4 combined with a droplet-tracking model. The main purposes of the tests were to investigate, respectively, the influence of containment sprays on mixing of the stratified atmosphere and on atmosphere depressurization. Two- and three-dimensional models of the TOSQAN vessel for the CFX4.4 code were developed. The modelling approach is based on an Eulerian description of the continuous phase (gas), a Lagrangian description of the dispersed phase (spray droplets), and a two-way interaction between the phases. Droplets act as sources or sinks of energy, mass and momentum in the single-phase gaseous field. In addition, a simple droplet–wall interaction model was incorporated into the code, allowing the evaporation of the liquid film formed by deposited droplets. The results of the simulations are compared to experimental data. For test TOSQAN 113, the emphasis is on the comparison of non-homogeneous helium distribution, whereas for test TOSQAN 101, the emphasis is on the comparison of pressure and non-homogeneous temperature distribution. The comparisons of experimental and simulation results of both tests support the adequacy of the combined CFD and droplet-tracking approach.

The next generation of iron fertilization experiments in the Southern Ocean

Of the various macro-engineering schemes proposed to mitigate global warming, ocean iron fertilization (OIF) is one that could be started at short notice on relevant scales. It is based on the reasoning that adding trace amounts of iron to iron-limited phytoplankton of the Southern Ocean will lead to blooms, mass sinking of organic matter and ultimately sequestration of significant amounts of atmospheric carbon dioxide (CO2) in the deep sea and sediments. This iron hypothesis, proposed by John Martin in 1990 (Martin 1990 Paleoceanography 5, 1-13), has been tested by five mesoscale experiments that provided strong support for its first condition: stimulation of a diatom bloom accompanied by significant CO2 drawdown. Nevertheless, a number of arguments pertaining to the fate of bloom biomass, the ratio of iron added to carbon sequestered and various side effects of fertilization, continue to cast doubt on its efficacy. The idea is also unpopular with the public because it is perceived as meddling with nature. However, this apparent consensus against OIF is premature because none of the published experiments were specifically designed to test its second condition pertaining to the fate of iron-induced organic carbon. Furthermore, the arguments on side effects are based on worst-case scenarios. These doubts, formulated as hypotheses, need to be tested in the next generation of OIF experiments. We argue that such experiments, if carried out at appropriate scales and localities, will not only show whether the technique will work, but will also reveal a wealth of insights on the structure and functioning of pelagic ecosystems in general and the krill-based Southern Ocean ecosystem, in particular. The outcomes of current models on the efficacy and side effects of OIF differ widely, so data from adequately designed experiments are urgently needed for realistic parametrization. OIF is likely to boost zooplankton stocks, including krill, which could have a positive effect on recovery of the great whale populations. Negative effects of possible commercialization of OIF can be controlled by the establishment of an international body headed by scientists to supervise and monitor its implementation.

Cd/Ca ratios of in situ collected planktonic foraminiferal tests

The Cd/Ca ratios of planktonic foraminiferal tests have been used to reconstruct surface water nutrient utilization and paleoproductivity. The reliability of this proxy has hitherto not been comprehensively studied, however. To fill this gap, we present novel Cd/Ca data for in situ sampled and sedimentary planktonic foraminifers of the species Globigerinoides ruber, G. sacculifer, Globigerina bulloides, Orbulina universa, and Globorotalia truncatulinoides from the Arabian Sea and the North Atlantic. The Cd/Ca ratios obtained for G. ruber sampled from the live habitat generally display a correlation with seawater phosphate content, but no such trend is observed for G. sacculifer. This distinct behavior may reflect different ecological niches or species‐specific incorporation of Cd into the calcite shells of the organisms. The Cd/Ca ratios of G. ruber, G. sacculifer, and G. bulloides from surface sediments are consistently higher than those obtained for live collected specimens of the same species. Postdepositional alteration of the tests is unlikely to be responsible for these systematic differences. Rather, they appear to reflect a combination of factors, including the formation of calcite crusts with high Cd contents, the different timescales that are represented by in situ and sedimentary foraminiferal tests, and the dominance of tests from periods of high productivity in sediments. Our results also reveal higher Cd/Ca ratios for live G. ruber than for settling tests of the same species. This suggests that planktonic foraminiferal shells are partially dissolved while they individually settle through the water column. Sedimentary tests, however, will be less affected by dissolution processes because these shells are primarily deposited in mass sinking events, which feature much higher settling velocities than those experienced by single settling shells.

Particle Deposition Onto Rough Surfaces

Predictions for the number of particles depositing from fully developed turbulence onto a fully roughened k-type surface are obtained from the results of large-eddy simulations for a ribbed-channel flow. Simulation data are found to provide only partial support for the “mass-sink hypothesis,” i.e., the notion that all particles entering a mass sink, a volume of fluid extending vertically from the deposition surface, are captured and eventually deposited. The equality of the number of particles entering the mass sink and the number of particles depositing is attained, and a qualitative agreement with the empirical model of Wood (1981, “A Simple Method for the Calculation of Turbulent Deposition to Smooth and Rough Surfaces,” J. Aerosol Sci., 12(3), pp. 275–290) for the height of this mass sink is obtained. However, a significant proportion of particles escapes from the mass sink and the equality of numbers is attained only because many particles deposit onto rib surfaces above the mass sink, without first entering the mass sink.

Multi‐layer arctic mixed‐phase clouds simulated by a cloud‐resolving model: Comparison with ARM observations and sensitivity experiments

A cloud‐resolving model (CRM) is used to simulate the multiple‐layer mixed‐phase stratiform (MPS) clouds that occurred during a three‐and‐a‐half day subperiod of the Department of Energy‐Atmospheric Radiation Measurement Program's Mixed‐Phase Arctic Cloud Experiment (M‐PACE) and to examine physical processes responsible for multilayer production and evolution. The CRM with a two‐moment cloud microphysics is initialized with concurrent meteorological, aerosol, and ice nucleus measurements and is driven by time‐varying large‐scale advective tendencies of temperature and moisture and surface sensible and latent heat fluxes. The CRM reproduces the dominant occurrences of the single‐ and double‐layer MPS clouds as revealed by the M‐PACE observations although the simulated first cloud layer is lower and the second cloud layer is thicker compared to observations. The aircraft measurements suggest that the CRM qualitatively captures the major characteristics in the vertical distribution and interperiod variation of liquid water content (LWC), droplet number concentration, total ice water content (IWC), and ice crystal number concentration (nis). However, the magnitude of LWC is overestimated and those of IWC and nis are underestimated. In particular, the simulated nis is one order of magnitude smaller than the observed. Sensitivity experiments suggest that both the surface fluxes and large‐scale advection control the formation of the lower cloud layer while the large‐scale advection initiates the formation of the upper cloud layer but the maintenance of multilayer structures relies on the longwave (LW) radiative effect. The LW cooling near cloud top produces a more saturated environment and a stronger dynamical circulation while cloud base radiative warming of the upper layer creates the stability gap between the two cloud layers. Both cloud layers are sensitive to ice‐forming nuclei number concentration since ice‐phase microphysics provides a strong sink of cloud liquid water mass.

Surface tension dominated impact

We study the impact of a line mass onto a liquid-gas interface. At early times we find a similarity solution for the interfacial deformation and show how the resulting surface tension force slows the fall of the mass. We compute the motion beyond early times using a boundary integral method, and find conditions on the weight and impact speed of the mass that determine whether it sinks or is trapped by the interface. We find that for given impact speed there is a critical weight above which the mass sinks, and we investigate the asymptotic behavior of this critical weight in the limits of small and large impact speeds. Below this critical weight, the mass is trapped by the interface and subsequently floats. We also compare our theoretical results with some simple tabletop experiments. Finally, we discuss the implications of our work for the vertical jumps of water-walking arthropods.

Three‐year investigations into sperm whale‐fall ecosystems in Japan

AbstractWe report the first study of sperm whale‐fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2‐year period on replicate sperm‐whale carcasses implanted at depths of 219–254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis‐based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep‐water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep‐water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale‐fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls.

大形チャンバー法による木製家具からのホルムアルデヒド放散量測定

The formaldehyde emission from wood furniture have large influence upon indoor air quality. In this study, a simple large scale chamber was developed for measuring chemical emission from actual-sized furniture. Mass transfer coefficient and sink rate were examined. Formaldehyde emission from five wood products were measured by both large chamber and 20 L small chamber at same n/L condition. The results gave consistent formaldehyde concentration between both chambers. Air stirring in large chamber increased formaldehyde emission from bookshelf-shaped specimen, although it did not effect emission from flat-formed specimen. Formaldehyde emission from wooden furniture was measured by the large chamber. Most of newly made furniture gave comparatively low emission. Some of school furniture considered to be made approximately 10 years ago showed high emission.

Modeling of containment atmosphere mixing and stratification experiment using a CFD approach

An experiment on containment atmosphere mixing and stratification, which was originally performed in the TOSQAN facility in Saclay (France), was simulated with the Computational Fluid Dynamics code CFX4.4. The TOSQAN facility consists of a large cylindrical vessel in which gases are injected. In the considered experiment, steam, air and helium were injected during different phases of the experiment, with steam condensing on some parts of the vessel walls. During certain phases, steady states were obtained when the steam condensation rate became equal to the steam injection rate, with all boundary conditions remaining constant. In the present work, three such intermediate steady states were simulated independently. The essential purpose was to reproduce the non-homogeneous structure of the vessel atmosphere, given that condensation is simulated in such a way to obtain the proper condensation rate. A two-dimensional axisymmetric model of the TOSQAN vessel for the CFX4.4 code was developed. The flow in the simulation domain was modeled as single-phase. Steam condensation on vessel walls was modeled as a sink of mass and energy. Calculated profiles of temperature, steam concentration, and velocity components are compared to experimental results and discussed. The comparison suggests that atmosphere mixing and stratification in an NPP containment at accident conditions could be successfully simulated using the proposed CFD approach.

Gas Flow across Gaps in Protoplanetary Disks

We analyze the gas accretion flow through a planet-produced gap in a protoplanetary disk. We adopt the alpha disk model and ignore effects of planetary migration. We develop a semi-analytic, one-dimensional model that accounts for the effects of the planet as a mass sink and also carry out two-dimensional hydrodynamical simulations of a planet embedded in a disk. The predictions of the mass flow rate through the gap based on the semi-analytic model generally agree with the hydrodynamical simulations at the 25% level. Through these models, we are able to explore steady state disk structures and over large spatial ranges. The presence of an accreting Jupiter-mass planet significantly lowers the density of the disk within a region of several times the planet's orbital radius. The mass flow rate across the gap (and onto the central star) is typically 10% to 25% of the mass accretion rate outside the orbit of the planet, for planet-to-star mass ratios that range from 5e-5 to 1e-3.

Mathematical modelling of solvent drying from a static particle bed

Distributed-parameter models of vacuum contact drying of a static particle bed have been formulated and a numerical solution of the resulting set of partial differential equations describing heat and mass transfer in the particle bed has been carried out. Systematic parametric study of the effect of jacket temperature, head-space pressure, bed depth, and gas- and liquid-phase relative permeability has been performed. Trends observed in vacuum contact drying experiments, namely the independence of drying rate on the mode of driving force realisation (by jacket temperature or head-space pressure), linear scaling of heat-transfer rate with bed depth during the constant-rate period, independence of drying rate on particle size above a certain critical size, and disappearance of the constant-rate period below a certain particle size, have been reproduced by the model both qualitatively and quantitatively. A study of the effect of gas-phase permeability on drying kinetics revealed an interesting phenomenon–a reversal of the direction of drying front propagation. The drying front was found to originate from the heat source (heated walls) for large permeability, and from the mass sink (head-space) for low permeability.

The Orbital Statistics of Stellar Inspiral and Relaxation near a Massive Black Hole: Characterizing Gravitational Wave Sources

We study the orbital parameter distribution of stars that are scattered into nearly radial orbits and then spiral into a massive black hole (MBH) due to dissipation, in particular by emission of gravitational waves (GWs). This is important for GW detection, e.g., by the Laser Interferometer Space Antenna (LISA). Signal identification requires knowledge of the waveforms, which depend on the orbital parameters. We use analytical and Monte Carlo methods to analyze the interplay between GW dissipation and scattering in the presence of a mass sink during the transition from the initial scattering-dominated phase to the final dissipation-dominated phase of the inspiral. Our main results are as follows. (1) Stars typically enter the GW-emitting phase with high eccentricities. (2) The GW event rate per galaxy is a few × 10-9 yr-1 for typical central stellar cusps, almost independently of the relaxation time or the MBH mass. (3) For intermediate-mass black holes of ~103 M☉ such as may exist in dense stellar clusters, the orbits are very eccentric and the inspiral is rapid, so the sources are very short-lived.

Dynamics of Mass-Loaded Wind

The structure of a steady state, spherically symmetric flow with a distributed mass source and sink is examined in this paper: the source corresponds to the arrival of mass from vaporizing clouds and the sink, to the possible condensation of gas owing to a thermal instability. Depending on the efficiency of the mass source, three types of flow can exist: (a) supersonic or subsonic flows everywhere, and flows with (b) one or (c) two critical (sonic) points. Condensation of the gas shifts the critical point (if it exists) outward. External gravitation does not change the flow structure qualitatively, unlike in the case of flows without mass sources and sinks.

The Importance of the Precipitation Mass Sink in Tropical Cyclones and Other Heavily Precipitating Systems

When water vapor is converted to cloud and precipitation and subsequently removed to the surface via precipitation, there is a corresponding hydrostatic pressure decrease due to the reduction of mass in the overlying column. Pressure changes resulting from the addition or removal of water vapor are currently neglected in most meteorological applications. However, in heavily precipitating systems such as tropical cyclones, where precipitation rates may exceed 250 mm day−1, the pressure equivalent of the precipitation mass sink is not negligible (∼25 hPa day−1). Pressure decreases due to this mechanism are most pronounced in the lower troposphere, particularly below the melting level. The resulting unbalanced pressure-gradient force can enhance convergence, which precludes full realization of the pressure decrease but may contribute to vorticity generation and moisture convergence. The importance of the precipitation mass sink is investigated for the case of Hurricane Lili (2002) through the computation of mass and potential vorticity (PV) budgets and numerical sensitivity experiments. The precipitation mass reaching the surface within 100 km of the storm center is of the same order as the mass loss needed to explain the area-averaged pressure decrease during the intensification stage of Lili. The PV is altered by precipitation mass flux divergence across isentropic layers. A volume-integrated PV budget reveals that the mass sink term is small in comparison to the latent heating term, although the latter exhibits large cancellation. Comparison of a control simulation from the Eta Model to an experimental simulation in which the precipitation mass sink effect is included demonstrates that the mass sink mechanism contributes to lower pressure, stronger wind speeds, and heavier precipitation. The sea level pressure near the storm center in the mass sink simulation is generally 2–5 hPa deeper relative to the control simulation, with 10-m wind speed differences of 5 to 15 kt. The mass sink simulation exhibits a stronger cyclonic PV tower, especially above the melting level, and a stronger troposphere–deep cyclonic circulation relative to the control simulation. The analysis presented indicates that the precipitation mass sink mechanism, though not dominant, is not negligible for tropical cyclones.

A review of major progresses in mesoscale dynamic research in China since 1999

Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed. Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale analysis and the perturbation method which are suitable for describing mesoscale vortices; (b) subcritical instability and vortex-sheet instability; (c) frontal adjustment mechanism and the effect of topography on frontgenesis; and (d) slantwise vorticity development theories, the slantwise vortex equation, and moist potential vorticity (MPV) anomalies with precipitation-related heat and mass sinks and MPV impermeability theorem. From the MPV conservation viewpoint, the transformation mechanism between different scale weather systems is analyzed. Based on the data analysis, a new dew-point front near the periphery of the West Pacific subtropical high is identified. In the light of MPV theory and Q-vector theory, some events associated with torrential rain systems and severe storms are analyzed and diagnosed. Progress in mesoscale numerical simulation has been made in the development of meso-α, meso-β vortices, meso-γ-scale downbursts and precipitation produced by deep convective systems with MM5 and other mesoscale models.

Aldehyde suppression of copepod recruitment in blooms of a ubiquitous planktonic diatom.

The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering copepod populations to track them temporally. We tested an alternative explanation: that dominant diatom species impair the reproductive success of their grazers. We compared larval development of a common overwintering copepod fed on a ubiquitous, early-blooming diatom species with its development when fed on a typical post-bloom dinoflagellate. Development was arrested in all larvae in which both mothers and their larvae were fed the diatom diet. Mortality remained high even if larvae were switched to the dinoflagellate diet. Aldehydes, cleaved from a fatty acid precursor by enzymes activated within seconds after crushing of the cell, elicit the teratogenic effect. This insidious mechanism, which does not deter the herbivore from feeding but impairs its recruitment, will restrain the cohort size of the next generation of early-rising overwinterers. Such a transgenerational plant-herbivore interaction could explain the recurringly inefficient use of a predictable, potentially valuable food resource--the spring diatom bloom--by marine zooplankton.

Vortex Funnel Formation by a Mass Sink within the Shallow-Water Model

The problem of the evolution of an axisymmetric vortex in the presence of given mass sinks is considered within the shallow-water model. Using the cyclostrophic balance approximation, i.e. the balance between pressure gradient and centrifugal force, the nonlinear process of development of a steady vortex flow regime (vortex funnel) is described.

Moisture Transport and Other Hydrometeorological Features Associated with the Severe 2000/01 Drought over the Western and Central Canadian Prairies

The 54-yr (1948–2001) NCEP–NCAR reanalysis data as well as other information were used to study the moisture transport and associated circulation features for the severe 2000/01 drought over the western and central Canadian Prairies. Most of the moisture for precipitation over the region is from the Pacific Ocean in winter (November–March) and from the Gulf of Mexico in summer (May–August). An analysis shows that the zonal moisture transport from the Pacific Ocean into both the North American continent and the western and central Canadian Prairies during the winter of the 2000/01 agricultural year was the least over the entire study period, and there was no significantly enhanced moisture influx from the Gulf of Mexico into the region to compensate. Very low winter precipitation was produced over the western and central Canadian Prairies as a consequence. During the ensuing summer period, moisture transport from the Gulf of Mexico was significantly less than normal and no significantly enhanced moisture transport from the Pacific Ocean occurred. These conditions collectively resulted in extremely dry surface conditions for the growing season. These moisture transport features were mainly associated with prolonged and extraordinarily strong anomalously high pressures over western North America and their related stronger-than-normal air mass sinking over the western and central prairies and adjacent regions. The anomalous high pressures blocked the moisture from flowing into the western and central prairies and were also associated with the splitting of the jet stream that significantly reduced zonal moisture transport by changing the strength and incoming angle of the airflows from the Pacific Ocean during the winter of 2000/01. Consequences of the stronger-than-normal subsidence were hot and dry surface air during the summer and less precipitation. Collectively, these dynamic factors are favorable for both the formation and the maintenance of droughts.

Theory and numerics of geometrically non‐linear open system mechanics

AbstractThe present contribution aims at deriving a general theoretical and numerical framework for open system thermodynamics. The balance equations for open systems differ from the classical balance equations by additional terms arising from possible local changes in mass. In contrast to existing formulations, these changes not only originate from additional mass sources or sinks but also from a possible in‐ or outflux of matter. Constitutive equations for the mass source and the mass flux are discussed for the particular model problem of bone remodelling in hard tissue mechanics. Particular emphasis is dedicated to the spatial discretization of the coupled system of the balance of mass and momentum. To this end we suggest a geometrically non‐linear monolithic finite element based solution technique introducing the density and the deformation map as primary unknowns. It is supplemented by the consistent linearization of the governing equations. The resulting algorithm is validated qualitatively for classical examples from structural mechanics as well as for biomechanical applications with particular focus on the functional adaption of bones. It turns out that, owing to the additional incorporation of the mass flux, the proposed model is able to simulate size effects typically encountered in microstructural materials such as open‐pored cellular solids, e.g. bones. Copyright © 2003 John Wiley & Sons, Ltd.