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As magma ascends and decompresses, volatiles exsolve and volume fraction of gas increases. As a result, magma fragmentation occurs and the flow changes from bubbly flow to gaspyroclast flow. In our model, a transitional region (\u0026apos;permeable flow region\u0026apos;) is introduced between the bubbly flow region and the gaspyroclast flow region. In this region. both the gas and the liquid are continuous phases, allowing the efficient vertical escape of gas through the permeable structure. We describe the features of conduit flow with relative motion of gas and liquid using nondimensional numbers alpha, gamma and epsilon. The parameter a represents the ratio of effects of wall friction to gravitational load, and is proportional to magma flow rate. The parameter gamma represents the degree of decompression for the gaspyroclast flow to reach the sound velocity at alpha = 1, and is proportional to r(c)(2)/mu for given magma temperature and initial volatile content, where r(c) is conduit radius and mu is liquid viscosity. The parameter epsilon is defined as the ratio of liquidwall friction force to liquidgas interaction force in the permeable flow region, and represents the efficiency of gas escape from magma. The values of gamma and epsilon are determined only by magma properties and geological conditions such as liquid viscosity, magma permeability and conduit radius. We formulate a 1dimensional steadystate conduit flow model to find nondimensional magma flow rate a as a function of magma properties and geological conditions (e.g., gamma and epsilon) under given boundary conditions. When the relative motion is taken into account with the assumption that magma fragmentation occurs when the gas volume fraction reaches some critical values, the pressure at the fragmentation level (P(f)) decreases as the magma flow rate (alpha) decreases or the efficiency of gas escape (epsilon) increases, because gas escape suppresses the increase in the gas volume fraction accompanying magma ascent. When epsilon is so large that P(f) is below the atmospheric pressure (P(a)), the flow reaches the vent before fragmentation at low a. On the other hand, when epsilon is so small that P(f) is greater than P(a), the flow reaches the vent after fragmentation at high alpha. These steadystate solutions of the flow at low and high alpha correspond to effusive and explosive eruptions, respectively. We present a graphical method to systematically find alpha. On the basis of the graphical method, a simple regime map showing the relationship between the assemblage of the solutions of conduit flow and the magma properties or the geological conditions is obtained, (C) 2008 Elsevier B.V. All rights reserved.", "subitem_description_language": "en", "subitem_description_type": "Other"}]}, "item_10001_publisher_8": {"attribute_name": "出版者", "attribute_value_mlt": [{"subitem_publisher": "ELSEVIER SCIENCE BV", "subitem_publisher_language": "en"}]}, "item_10001_relation_14": {"attribute_name": "DOI", "attribute_value_mlt": [{"subitem_relation_type_id": {"subitem_relation_type_id_text": "10.1016/j.jvolgeores.2008.11.006"}}]}, "item_10001_source_id_9": {"attribute_name": "ISSN", "attribute_value_mlt": [{"subitem_source_identifier": "03770273", "subitem_source_identifier_type": "ISSN"}]}, "item_creator": {"attribute_name": "著者", "attribute_type": "creator", "attribute_value_mlt": [{"creatorNames": [{"creatorName": "T. 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An analytical method", "subitem_title_language": "en"}]}, "item_type_id": "40001", "owner": "1", "path": ["1670839190650"], "permalink_uri": "https://niedrepo.bosai.go.jp/records/4317", "pubdate": {"attribute_name": "PubDate", "attribute_value": "20230427"}, "publish_date": "20230427", "publish_status": "0", "recid": "4317", "relation": {}, "relation_version_is_last": true, "title": ["Effects of relative motion between gas and liquid on 1dimensional steady flow in silicic volcanic conduits: 1. An analytical method"], "weko_shared_id": 1}
Effects of relative motion between gas and liquid on 1dimensional steady flow in silicic volcanic conduits: 1. An analytical method
https://niedrepo.bosai.go.jp/records/4317
https://niedrepo.bosai.go.jp/records/4317eb4fbcf791794cc69c84da4fac52206c
Item type  researchmap(1)  

公開日  20230427  
タイトル  
言語  ja  
タイトル  Effects of relative motion between gas and liquid on 1dimensional steady flow in silicic volcanic conduits: 1. An analytical method  
タイトル  
言語  en  
タイトル  Effects of relative motion between gas and liquid on 1dimensional steady flow in silicic volcanic conduits: 1. An analytical method  
言語  
言語  eng  
著者 
T. Kozono
× T. Kozono
× T. Koyaguchi


抄録  
内容記述タイプ  Other  
内容記述  We investigate the effects of vertical relative motion between gas and liquid on eruption styles by formulating a model for 1dimensional steady flow in volcanic conduits. As magma ascends and decompresses, volatiles exsolve and volume fraction of gas increases. As a result, magma fragmentation occurs and the flow changes from bubbly flow to gaspyroclast flow. In our model, a transitional region ('permeable flow region') is introduced between the bubbly flow region and the gaspyroclast flow region. In this region. both the gas and the liquid are continuous phases, allowing the efficient vertical escape of gas through the permeable structure. We describe the features of conduit flow with relative motion of gas and liquid using nondimensional numbers alpha, gamma and epsilon. The parameter a represents the ratio of effects of wall friction to gravitational load, and is proportional to magma flow rate. The parameter gamma represents the degree of decompression for the gaspyroclast flow to reach the sound velocity at alpha = 1, and is proportional to r(c)(2)/mu for given magma temperature and initial volatile content, where r(c) is conduit radius and mu is liquid viscosity. The parameter epsilon is defined as the ratio of liquidwall friction force to liquidgas interaction force in the permeable flow region, and represents the efficiency of gas escape from magma. The values of gamma and epsilon are determined only by magma properties and geological conditions such as liquid viscosity, magma permeability and conduit radius. We formulate a 1dimensional steadystate conduit flow model to find nondimensional magma flow rate a as a function of magma properties and geological conditions (e.g., gamma and epsilon) under given boundary conditions. When the relative motion is taken into account with the assumption that magma fragmentation occurs when the gas volume fraction reaches some critical values, the pressure at the fragmentation level (P(f)) decreases as the magma flow rate (alpha) decreases or the efficiency of gas escape (epsilon) increases, because gas escape suppresses the increase in the gas volume fraction accompanying magma ascent. When epsilon is so large that P(f) is below the atmospheric pressure (P(a)), the flow reaches the vent before fragmentation at low a. On the other hand, when epsilon is so small that P(f) is greater than P(a), the flow reaches the vent after fragmentation at high alpha. These steadystate solutions of the flow at low and high alpha correspond to effusive and explosive eruptions, respectively. We present a graphical method to systematically find alpha. On the basis of the graphical method, a simple regime map showing the relationship between the assemblage of the solutions of conduit flow and the magma properties or the geological conditions is obtained, (C) 2008 Elsevier B.V. All rights reserved.  
言語  en  
書誌情報 
en : Journal of Volcanology and Geothermal Research 巻 180, 号 1, p. 2136, 発行日 200902 

出版者  
言語  en  
出版者  ELSEVIER SCIENCE BV  
ISSN  
収録物識別子タイプ  ISSN  
収録物識別子  03770273  
DOI  
関連識別子  10.1016/j.jvolgeores.2008.11.006 