Ash Transport Research Articles

Operational Modelling of Umbrella Cloud Growth in a Lagrangian Volcanic Ash Transport and Dispersion Model

Large explosive eruptions can result in the formation of an umbrella cloud which rapidly expands, spreading ash out radially from the volcano. The lateral spread by the intrusive gravity current dominates the transport of the ash cloud. Hence, to accurately forecast the transport of ash from large eruptions, lateral spread of umbrella clouds needs to be represented within volcanic ash transport and dispersion models. Here, we describe an umbrella cloud parameterisation which has been implemented into an operational Lagrangian model and consider how it may be used during an eruption when information concerning the eruption is limited and model runtime is key. We examine different relations for the volume flow rate into the umbrella, and the rate of spreading within the cloud. The scheme is validated against historic eruptions of differing scales (Pinatubo 1991, Kelud 2014, Calbuco 2015 and Eyjafjallajökull 2010) by comparing model predictions with satellite observations. Reasonable predictions of umbrella cloud spread are achieved using an estimated volume flow rate from the empirical equation by Bursik et al. and the observed eruption height. We show how model predictions can be refined during an ongoing eruption as further information and observations become available.

Early atmospheric contamination on the top of the Himalayas since the onset of the European Industrial Revolution

Because few ice core records from the Himalayas exist, understanding of the onset and timing of the human impact on the atmosphere of the "roof of the world" remains poorly constrained. We report a continuous 500-y trace metal ice core record from the Dasuopu glacier (7,200 m, central Himalayas), the highest drilling site on Earth. We show that an early contamination from toxic trace metals, particularly Cd, Cr, Mo, Ni, Sb, and Zn, emerged at high elevation in the Himalayas at the onset of the European Industrial Revolution (∼1780 AD). This was amplified by the intensification of the snow accumulation (+50% at Dasuopu) likely linked to the meridional displacement of the winter westerlies from 1810 until 1880 AD. During this period, the flux and crustal enrichment factors of the toxic trace metals were augmented by factors of 2 to 4 and 2 to 6, respectively. We suggest this contamination was the consequence of the long-range transport and wet deposition of fly ash from the combustion of coal (likely from Western Europe where it was almost entirely produced and used during the 19th century) with a possible contribution from the synchronous increase in biomass burning emissions from deforestation in the Northern Hemisphere. The snow accumulation decreased and dry winters were reestablished in Dasuopu after 1880 AD when lower than expected toxic metal levels were recorded. This indicates that contamination on the top of the Himalayas depended primarily on multidecadal changes in atmospheric circulation and secondarily on variations in emission sources during the last 200 y.

Role of rheology on the hydraulic transportation of lignite coal and coal ash slurries in the pipeline

ABSTRACT The transportation of Lignite coal and Coal ash in slurry form through pipelines is economically and environmentally more viable than the other conventional modes of transportation. The main focus of the present work is to demonstrate the effect of particle concentration and size on the rheological properties of slurries and to further investigate the head loss, energy consumption, energy cost, and transport capacity during slurry transport through pipes. The rheology data indicate the shear thinning flow behavior for all particle concentrations and sizes examined in the shear rate () range of 10–500 s−1. The high viscosity of slurry containing fine particles can be reduced by introducing an optimum concentration of coarse particles, which subsequently results in lower head loss, energy consumption, and cost. A Power-law model is fitted to rheological flow curves in order to obtain flow behavior index (n) and consistency coefficient (k), which are then used to calculate specific energy consumption and head loss. The energy cost in USD per ton per 100 km is calculated from the specific energy consumption and is found to be substantially cheaper than the existing rail and road transportation costs in India.

Aeolian Remobilisation of the 2011-Cordón Caulle Tephra-Fallout Deposit: Example of an Important Process in the Life Cycle of Volcanic Ash

Although volcanic eruptions represent short periods in the whole history of a volcano, the large amount of loose pyroclastic material produced, combined with aeolian processes, can lead to continuous, long-lasting reworking of volcanic products. Driven by wind, these processes significantly influence the geomorphology and prolong the impacts of eruptions on exposed communities and ecosystems. Since such phenomena are of interest to scientists from a range of disciplines (e.g. volcanology, atmospheric and soil sciences), a well-defined, common nomenclature is necessary to optimize the multidisciplinary characterisation of both processes and deposits. We, therefore, first describe ash wind-remobilisation processes and provide definitions for appropriate terms consistent with the World Meteorological Organization’s classification of lithometeors. Secondly, we investigate the aeolian transport and deposition of ash from the 2011 Cordόn Caulle (Chile) tephra-fallout through field observations and on a physical characterisation of systematically collected ground and airborne material. In the arid regions of the Argentinian Patagonia steppe, two main types of secondary deposits have been identified associated with: i) non-erodible surface roughness elements (e.g. vegetation and rocks), and ii) pre-existing mounds or similar erodible bedforms. Grainsize analysis shows that wind-remobilised particles have a specific size range, from <0.4 to 500 m, with a 95% of the material between 1 and 255 m, median values of 25-135 m and modes of 30-95 m. We find that 15-40% of the remobilised material ranges from 63-125 m, coinciding with the size range which minimises the wind threshold friction velocity. Interestingly, particle shape analysis shows that for this size fraction, remobilised particles display the largest differences in shape descriptors (convexity, solidity and circularity) with respect to the primary ash, indicating abrasion and rounding due to saltation. Although particle (size and shape) and deposit features (morphology and structures) alone are insufficient to interpret transport mechanisms, their combination suggests that whilst saltation is the most common particle transport mechanism, suspension and creep also play an important role. In fact, our results suggest that saltation induces short-term suspension of fine particles (20-63 m).

Impact of pollutants in the energy sector on the environment and technologies for treating liquid and solid waste from power plants

The main pollutants in the soil are composed of ash, clay, and calcium sulfur, which results from the desulfurization of flue gases. However, the infiltration of liquid fuels and lubricants, as well as transformation oil, may be neglected. Liquid residues result from several technological processes. The main source of pollution is the water treatment process that must be used in the water-steam circuit. Another important source of liquid residues is the cooling process of the thermal agent. A third major source of water pollution is the flue gas desulphurization process and the transport of slag and ash. Thus, it should not be neglected that power plants are large industrial installations, which require permanent maintenance, liquid residues resulting from cleaning operations of various equipment. To have the technology for treatment, disposal and storage of high-efficiency waste, we must take into account the following factors: the volume and type of waste, their properties, the likely evolution of the installation, the volume of waste generated by it, treatment possibilities and even limits imposed by environmental regulations.

Effect of swirl vanes angle on erosion behaviour of AISI 316 pipe bend

Erosion wear is one of the major problems in thermal power plant components involving coal ash transportation viz., pipe line, pipe bends, valves, slurry pumps casing and impeller due to high velocity ash slurry flows, which reduces the life of the components and increases the expenditure incurred of the plant. In the current study the effect of induced swirl on erosion wear due to different swirl vanes of inclination angles 7.5°, 11.25°, 15° and 30° has been investigated at a pipe bend. The erosion wear on a pipe bend without a swirl vane for particle size of 150 µm has been calculated for velocities of 10 m/s, 20 m/s and 30 m/s with erodent flow rates of 0.2 kg/s and 0.3 kg/s and compared against erosion rates when a swirl vane is placed upstream of the bend. The optimal distance of placing the vane has been found out by placing the vanes at a distance of 280 mm, 320 mm and 360 mm from inlet of the pipe. It is found that erosion wear decreases for all of the cases except when a 30° vane was introduced for a flow velocity of 30 m/s and 7.5° vane when placed at a distance of 360 mm from the inlet, is found to be the most effective for erosion reduction.

Potential CO2 reduction and cost evaluation in use and transport of coal ash as cement replacement: A case in the Philippines

Coal ash can potentially be utilized as partial replacement for cement in concrete and mortar formulations. The use of coal ash can lessen the cost and energy production, and reduce the impact on the environment. At present, the annual coal ash generation amounts to ~2.78 Mt and may reach to ~13.02 Mt by 2035 in the Philippines. If coal ash is utilized as clinker replacement in the production of cement at a clinker-to-cement ratio of 0.7, GHG emissions can potentially be reduced to at least ~1.26 Mt CO2_eq in 2018 and could further be reduced by ~5.89 Mt CO2_eq by 2035 when surplus coal ash is utilized as partial cement replacement in concrete mixtures in concrete batching plants. As transport of coal ash can also result in GHG emission owing to fuel combustion, a critical distance is calculated in order to achieve positive net reductions. Critical distance is obtained by comparing the emission on coal ash transportation with that of cement production, while taking into consideration the emissions of the return trip. Thus, transporting the coal ash is limited to a distance of ~2841 km. Existing concrete batching plants are situated within 2,000 km from existing coal-fired power plants, where the transport of coal ash to these plants would not result in additional emissions but instead result in annual net reduction of GHG. Further, the cost of coal ash per bag varies according to the distance travelled and is much lower than the cost of cement per bag.

PRODUCTION OF THERMAL INSULATION MATERIAL BASED ON VOLCANIC ASH DEPOSITS OF PRIMAGADANYA

Modern technologies are not standing still, and scientists are trying not only to invent new building materials, but also to find non-standard use of various raw materials that were previously considered unsuitable for use. Innovative technologies are actively used for modern construction of buildings, in particular, some types of new materials are used in the construction of various facilities. This is especially true in areas where it is not possible to import or use ordinary building materials for various reasons. Often, when designing a building, developers are wondering whether it is worth making the house warm during construction, and which insulation for the walls of the house is better to choose. This article addresses the question of which insulation for walls is most suitable for construction. The most common are mineral insulation, which are represented on the market today in the form of basalt slabs, fiberglass, etc. They have such advantages as low thermal conductivity, good thermal insulation and vapor permeability. The article presents a table with comparative performance characteristics of a mineral wool stone slab and a fiberglass slab. Stone or basalt wool has several advantages. It is able to withstand significant temperatures and temperature changes, the mats are easy to transport, convenient to install. In our opinion, a serious alternative to basalt in the production of thermal insulation materials is volcanic ash. One of the main features of volcanic ash are its building qualities, such as good thermal insulation and an environmentally friendly composition. Since here we are considering the possibility of producing insulation materials based on volcanic ash, we performed a thermal calculation of the enclosing structures. Also in the tables are the costs of transportation of volcanic ash from the field to the point of the proposed production of insulating material. Volcanic ash can be widely used in countries with high volcanic activity as an inexpensive raw material for the manufacture of building materials. It does not require additional processing and has a number of useful properties.

Far‐travelled ash in past and future eruptions: combining tephrochronology with volcanic studies

ABSTRACTStudies of recent eruptions have improved our understanding of volcanic ash transport and deposition, but have also raised important questions about the behaviour of far‐travelled (distal) volcanic ash. In particular, it is difficult to reconcile estimates of distal ash mass and transport distance determined from eyewitness accounts, mapped deposits, satellite‐based observations and cryptotephra records. Here we address this problem using data from well‐characterized eruptions that, collectively, include all four data types. Data from recent eruptions allow us to relate eyewitness accounts to mapped deposits on the ground and satellite‐based observations of ash in the air; observations from an historical eruption link eyewitness accounts to cryptotephra deposits. Together these examples show that (i) 10–20% of the erupted mass is typically deposited outside the mapped limits; (ii) estimates of the ash mass transported in volcanic clouds cannot account for all of this unmapped ash; and (iii) ash fall observed at distances beyond mapped deposits can have measurable impacts, and can form cryptotephra deposits with high (&gt;~1000 cm−3) shard counts. We conclude that cryptotephra data can be incorporated into volcanological studies of ash transport and deposition and provide important insight into both the behaviour and impacts of far‐travelled volcanic ash particles.

Assessment of the potential for in-plume sulphur dioxide gas-ash interactions to influence the respiratory toxicity of volcanic ash

BackgroundVolcanic plumes are complex environments composed of gases and ash particles, where chemical and physical processes occur at different temperature and compositional regimes. Commonly, soluble sulphate- and chloride-bearing salts are formed on ash as gases interact with ash surfaces. Exposure to respirable volcanic ash following an eruption is potentially a significant health concern. The impact of such gas-ash interactions on ash toxicity is wholly un-investigated. Here, we study, for the first time, whether the interaction of volcanic particles with sulphur dioxide (SO2) gas, and the resulting presence of sulphate salt deposits on particle surfaces, influences toxicity to the respiratory system, using an advanced in vitro approach. MethodsTo emplace surface sulphate salts on particles, via replication of the physicochemical reactions that occur between pristine ash surfaces and volcanic gas, analogue substrates (powdered synthetic volcanic glass and natural pumice) were exposed to SO2 at 500 °C, in a novel Advanced Gas-Ash Reactor, resulting in salt-laden particles. The solubility of surface salt deposits was then assessed by leaching in water and geochemical modelling. A human multicellular lung model was exposed to aerosolised salt-laden and pristine (salt-free) particles, and incubated for 24 h. Cell cultures were subsequently assessed for biological endpoints, including cytotoxicity (lactate dehydrogenase release), oxidative stress (oxidative stress-related gene expression; heme oxygenase 1 and NAD(P)H dehydrogenase [quinone] 1) and its (pro-)inflammatory response (tumour necrosis factor α, interleukin 8 and interleukin 1β at gene and protein levels). ResultsIn the lung cell model no significant effects were observed between the pristine and SO2-exposed particles, indicating that the surface salt deposits, and the underlying alterations to the substrate, do not cause acute adverse effects in vitro. Based on the leachate data, the majority of the sulphate salts from the ash surfaces are likely to dissolve in the lungs prior to cellular uptake. ConclusionsThe findings of this study indicate that interaction of volcanic ash with SO2 during ash generation and transport does not significantly affect the respiratory toxicity of volcanic ash in vitro. Therefore, sulphate salts are unlikely a dominant factor controlling variability in in vitro toxicity assessments observed during previous eruption response efforts.

Respiratory Health in Adults Residing Near a Coal-Burning Power Plant with Coal Ash Storage Facilities: A Cross-Sectional Epidemiological Study.

Coal ash, the byproduct of burning coal made up of small particles, including heavy metals and radioactive elements, is discarded in open-air landfills where it can be emitted into the air, contributing to air pollution in the surrounding community. Few regulations exist regarding the storage, disposal, and transport of coal ash. There is limited research on the health impacts of coal ash exposure on communities. The purpose of this study was to examine the prevalence of respiratory symptoms among adults exposed to coal ash and non-exposed adults. A cross-sectional epidemiological study was conducted among two populations: one exposed to coal ash and one not exposed to coal ash. Perception of health (p-Value < 0.0001), cough (Adjusted Odds Ratio (AOR) = 5.30, 95% Confidence Intervals (CI) = 2.60–11), shortness of breath (AOR = 2.59, 95% CI = 1.56–4.31), hoarseness (AOR = 4.02, 95% CI = 2.45–6.60), respiratory infections (AOR = 1.82, 95% CI = 1.14–2.89), and mean overall respiratory health score (p-Value < 0.0001) were all statistically significantly greater in exposed adults (N = 231) when compared to non-exposed adults (N = 170). Adults residing near the coal ash facility were more likely to report respiratory symptoms than the non-exposed population. More research on the health impact of coal ash and storage regulations needs to be conducted.

Potential reduction of greenhouse gas emission through the use of sugarcane ash in cement-based industries: A case in the Philippines

Abstract Sugarcane ashes are wastes generated during the combustion of sugarcane residues in cogeneration plants. With sugarcane being the Philippine's top produced crop and a renewable energy resource, generation of sugarcane ash is inevitable. The aims of this study are to assess the potential amount of sugarcane ashes the Philippines can generate, and evaluate the potential greenhouse gas reduction in the utilization of ashes as partial cement replacement in mortar and concrete. The annual potential ash generation could reach to ∼366 kt, ∼125 kt is sugarcane bagasse ash and ∼241 kt is sugarcane leaves ash. Only 68% (∼85 kt) of the sugarcane bagasse ash and 4% (∼9 kt) of the sugarcane leaves ash could be generated by existing cogeneration plants. The utilization of these ashes can reduce the emissions by ∼273 kt CO2-eq annually, while addressing its disposal issues. With the unique archipelagic situation of the Philippines, the distribution of sugarcane ash was investigated, considering the transport emissions when later adopted as raw material in formulating mortar and concrete. Critical distances for transport of sugarcane ash without incurring additional emissions were 1,851 to 4,770 km by land and 5,500 km by sea due to their different corresponding emission factors. The return trip of a given transport vehicle was accounted in the determination of the critical distance to provide realistic estimates. This study provides a quantitative basis for the use of renewable biomass-based resource, like sugarcane ash, to further reduce greenhouse gas emissions in the Philippines.

Integrated Monitoring of Volcanic Ash and Forecasting at Sakurajima Volcano, Japan

The Sakurajima volcano is characterized by frequent vulcanian eruptions at the Minamidake or Showa crater in the summit area. We installed an integrated monitoring system for the detection of volcanic ash (composed of remote sensing sensors XMP radars, lidar, and GNSS with different wave lengths) and 13 optical disdrometers on the ground covering all directions from the crater to measure drop size distribution and falling velocity. Campaign sampling of volcanic ash supports the conversion of particle counts measured by the disdrometer to the weight of volcanic ash. Seismometers and tilt/strain sensors were used to estimate the discharge rate of volcanic ash from the vents. XMP radar can detect volcanic ash clouds even under visual difficulty because of weather such as fog or clouds. A vulcanian eruption on November 13 was the largest event at the Sakurajima volcano in 2017; however, the volcanic plume was not visible due to clouds covering the summit. Radar revealed that the volcanic plume reached an elevation of 4.2–6.2 km. Post-fit phase residuals (PPR) from the GNSS analysis increased suddenly after the eruption, and large-PPR paths from the satellites to the ground-based receivers intersected each other at an elevation of 4.2 km. The height of the volcanic plume was also estimated from the discharge rate of volcanic ash to be 4.5 km, which is empirically related to seismic energy and the deflation volume obtained via ground deformation monitoring. Using the PUFF model, the weight of the ash-fall deposit was accurately forecast in the main direction of transport of the volcanic ash, which was verified by disdrometers. For further advances in forecasting of the ash-fall deposit, we must consider high-resolution wind field, shape of volcanic plume as the initial value, and the particle number distribution along the volcanic plume.

Recent Developments and Applications of Acoustic Infrasound to Monitor Volcanic Emissions

Volcanic ash is a well-known hazard to population, infrastructure, and commercial and civil aviation. Early assessment of the parameters that control the development and evolution of volcanic plumes is crucial to effective risk mitigation. Acoustic infrasound is a ground-based remote sensing technique—increasingly popular in the past two decades—that allows rapid estimates of eruption source parameters, including fluid flow velocities and volume flow rates of erupted material. The rate at which material is ejected from volcanic vents during eruptions, is one of the main inputs into models of atmospheric ash transport used to dispatch aviation warnings during eruptive crises. During explosive activity at volcanoes, the injection of hot gas-laden pyroclasts into the atmosphere generates acoustic waves that are recorded at local, regional and global scale. Within the framework of linear acoustic theory, infrasound sources can be modelled as multipole series, and acoustic pressure waveforms can be inverted to obtain the time history of volume flow at the vent. Here, we review near-field (&lt;10 km from the vent) linear acoustic wave theory and its applications to the assessment of eruption source parameters. We evaluate recent advances in volcano infrasound modelling and inversion, and comment on the advantages and current limitations of these methods. We review published case studies from different volcanoes and show applications to new data that provide a benchmark for future acoustic infrasound studies.

Environmental assessment of valorisation alternatives for woody biomass ash in construction materials

Ash generated during the combustion of woody biomass for energy production is an industrial waste that should be properly managed in order to minimise the respective environmental impacts. Woody biomass ash valorisation in construction materials to replace conventional materials is an alternative that has proven to be technically feasible. On the other hand, it can present potential environmental impacts that should be evaluated to support the choice of more sustainable alternatives. Thus, the purpose of this work is to assess the potential impacts of woody biomass ash valorisation of through incorporation in construction materials using life cycle assessment. The valorisation alternatives consider the incorporation of woody biomass ash in cement mortars, adhesive mortars, concrete blocks, and bituminous asphalts. In addition, a base scenario consisting of ash landfilling is also assessed. Four types of woody biomass ashes were considered, namely fly and bottom ashes generated in a vibrating grate and fly and bottom ashes generated in a fluidised bed. The impact assessment method used is that suggested in the International Reference Life Cycle Data System for selected impact categories. The results showed that the impacts of ash transport and pre-processing and the impacts of producing the avoided materials are factors that affect the net impact of the valorisation scenarios and should be considered in the end-of-life management of biomass ash. Nevertheless, all valorisation scenarios had a lower impact than landfilling in all the impact categories under study, resulting in a significant decrease of the environmental impacts in some scenarios.

Effect of transportation of fly ash: Life cycle assessment and life cycle cost analysis of concrete

The incorporation of fly ash into concrete may be limited by its quality, local availability, and additional cost incurred due to transportation. The specific objectives of this study are to: conduct an experimental program to evaluate the material properties for the four concrete mix designs considered for analysis (100GU, 25FA, 35FA, 50FA); identify environmental impact categories that are most greatly affected by material transportation; develop a life cycle assessment (LCA) model and a life cycle cost (LCC) model to respectively quantify the environmental and economic benefits and/or burdens that reflect the interplay between concrete mix designs and transportation of fly ash (up to 1000 km by truck). This analysis considers a study period of 100 years and is based on the proposed repair schedule. This study defines the ‘break-even distance’ as the maximum distance at which the LCA or LCC analysis results (i.e. environmental impact or cost) for concrete containing fly ash is lower than corresponding results for the 100GU concrete. Key outcomes of this study are: (i) ‘ecotoxicity’, ‘human toxicity (non-cancer)’, and ‘resources and fossil fuels’ are the most highly affected environmental impact categories by transportation of fly ash. In contrast, global warming potential was minimally affected. (ii) The break-even distance depends on the time to first repair (TFR), total volume of concrete required over 100 years of being in service and the percentage of cement replacement by fly ash. For both the LCA and LCC analysis, the concrete mix, 35FA, has the lowest break-even distance compared to the 25FA and 50FA. The fly ash mix designs ranked in order of least to most environmentally friendly and economically viable are: 35FA, 25FA, and 50FA. (iii) The break-even distances are longer for the LCC analysis compared to the LCA model results which indicates that the environmental impacts associated with the transportation of fly ash are more severe than the cost associated with the process, based on the analysis and assumptions in this study.

Ash Accumulation and Transport in Diesel Particulate Filters (Forth Report)

Ash Accumulation and Transport in Diesel Particulate Filters (Forth Report)

Tracing the provenance of volcanic ash in Permian–Triassic boundary strata, South China: Constraints from inherited and syn-depositional magmatic zircons

The Permian-Triassic boundary (PTB) mass extinction, the most severe biocrisis in Earth's history, is thought to have been triggered by catastrophic volcanic activity. PTB sections in South China contain numerous volcanic ash beds, the source of which is inferred to have been either the Siberian Traps Large Igneous Province (STLIP) or intraregional subduction-zone arc volcanism. In this study, the provenance of these ash beds is determined through a comprehensive analysis based on the geochronological and geochemical signatures of zircons from four PTB sections (Dongpan, Xinmin, Ganxi and Shangsi). Inherited zircons yielded U–Pb ages of 250–3521 Ma with major age clusters in the Permian, Carboniferous to Silurian, early Cambrian to Neoproterozoic, early Neoproterozoic to late Mesoproterozoic, and early Paleoproterozoic. The age spectrum of these zircons is similar to those of detrital zircons from sedimentary and magmatic rocks of the South China and Indochina cratons but different from those of the Siberian Craton, providing evidence for an intraregional source of the volcanic material. The trace-element, εHf(t), and δ18O signatures of syn-depositional magmatic zircons are consistent with an arc-related/orogenic setting. PTB sections in South China can be assigned to sectors based on the number and cumulative thickness of ash beds and the length of zircon crystals. Sector I (South) includes the Dongpan and Xinmin sections, which have cumulative ash-bed thicknesses of 0.86–1.14 m and average zircon lengths of 151–217 μm. Sector II (North) includes the Ganxi, Shangsi and Daxiakou sections, which have cumulative ash-bed thicknesses of 0.17–0.33 m and average zircon lengths of 82–104 μm. Sector III (Northeast) includes the Niushan and Meishan sections, which have cumulative ash-bed thicknesses of 0.1–0.14 m and average zircon lengths of 71–73 μm. Systematic trends toward fewer and thinner ash beds and as well as smaller zircon sizes from Sector I to Sector III indicate a paleo-northward or -northeastward direction of ash transport. Collectively, our findings provide evidence that the source of volcanic ash in South China PTB sections was intraregional subduction-zone arc volcanism along the convergent margin between the South China and Indochina cratons.

ディーゼルパティキュレートフィルタ内の アッシュ堆積および輸送に関する研究（第2 報）

ディーゼルパティキュレートフィルタ内の アッシュ堆積および輸送に関する研究（第2 報）

Plume-SPH 1.0: a three-dimensional, dusty-gas volcanic plume model based on smoothed particle hydrodynamics

Abstract. Plume-SPH provides the first particle-based simulation of volcanic plumes. Smoothed particle hydrodynamics (SPH) has several advantages over currently used mesh-based methods in modeling of multiphase free boundary flows like volcanic plumes. This tool will provide more accurate eruption source terms to users of volcanic ash transport and dispersion models (VATDs), greatly improving volcanic ash forecasts. The accuracy of these terms is crucial for forecasts from VATDs, and the 3-D SPH model presented here will provide better numerical accuracy. As an initial effort to exploit the feasibility and advantages of SPH in volcanic plume modeling, we adopt a relatively simple physics model (3-D dusty-gas dynamic model assuming well-mixed eruption material, dynamic equilibrium and thermodynamic equilibrium between erupted material and air that entrained into the plume, and minimal effect of winds) targeted at capturing the salient features of a volcanic plume. The documented open-source code is easily obtained and extended to incorporate other models of physics of interest to the large community of researchers investigating multiphase free boundary flows of volcanic or other origins. The Plume-SPH code (https://doi.org/10.5281/zenodo. 572819) also incorporates several newly developed techniques in SPH needed to address numerical challenges in simulating multiphase compressible turbulent flow. The code should thus be also of general interest to the much larger community of researchers using and developing SPH-based tools. In particular, the SPH−ε turbulence model is used to capture mixing at unresolved scales. Heat exchange due to turbulence is calculated by a Reynolds analogy, and a corrected SPH is used to handle tensile instability and deficiency of particle distribution near the boundaries. We also developed methodology to impose velocity inlet and pressure outlet boundary conditions, both of which are scarce in traditional implementations of SPH. The core solver of our model is parallelized with the message passing interface (MPI) obtaining good weak and strong scalability using novel techniques for data management using space-filling curves (SFCs), object creation time-based indexing and hash-table-based storage schemes. These techniques are of interest to researchers engaged in developing particles in cell-type methods. The code is first verified by 1-D shock tube tests, then by comparing velocity and concentration distribution along the central axis and on the transverse cross with experimental results of JPUE (jet or plume that is ejected from a nozzle into a uniform environment). Profiles of several integrated variables are compared with those calculated by existing 3-D plume models for an eruption with the same mass eruption rate (MER) estimated for the Mt. Pinatubo eruption of 15 June 1991. Our results are consistent with existing 3-D plume models. Analysis of the plume evolution process demonstrates that this model is able to reproduce the physics of plume development.