09:30 〜 09:45
[MIS13-03] 噴火時の桜島周辺気流の数値解析
キーワード：数値解析、周辺気流、噴火、桜島
1. Introduction
Volcanic eruption products such as ash, ciders, hazardous gas and so on sometimes cause disasters. Volcanic ash harms crops, traffics, transportations, human health and so on. Flying ciders, lapilli and volcanic blocks often cause loss of lives and structures so as the eruption of Mt. Ontake in September 2014 causing 63 deaths and missing persons [1]. Accurate prediction of the product’s distribution is necessary for prevention and mitigation of the disaster. The distribution of flying products is affected by the air flow around the volcano, therefore the prediction of the flow field is essential for the prevention and mitigation of the volcanic disasters.
The trajectory of the volcanic smoke, ash and the flying product is directly affected by the wind flow, resulting in a distribution of the density of eruption products. The flow field around the volcano varies with the meteorological condition, the topography and the surface roughness. And fluctuation of the flow affects the distribution of the density.
2. Outline of Calculation
We designed a numerical simulation of wind flow around Sakurajima Volcano. The large eddy simulation using the Smagorinsky model was used for calculating the turbulent flow fields. The spatial averaging was conducted to the governing equation of the fluid and the effect of drag caused by the surface roughness such as plants and the buildings are added to the governing equations as a canopy model [2]. The curvilinear coordinate system was used for generating the topography. The meteorological condition was introduced as an inflow condition with wind velocity and temperature field obtained from the mesoscale numerical weather prediction model WRF. The eruption was expressed as a blowout of hot air and the effect of buoyancy was introduced by Boussinesq approximation. The volcanic ash was calculated as a diffusion of scalar density.
3. Calculated Results
Turbulent wind flow around Sakurajima volcano with eruption was simulated. The distribution of plants and buildings on the ground surface was obtained from the GIS data base and field survey. Space-time variation of wind velocity, temperature and ash density was obtained as shown in Figure 1.
4. Conclusions
Numerical method of turbulent flow field around a volcano with eruption was presented. The effect of surface roughness, topography, meteorological condition and eruption was reflected to the simulated turbulent wind fields.
Reference
1. Oikawa, T.; Yamaoka, K.; Yoshimoto, M.; Nakada, S.; Takeshita, Y.; Maeno, F.; Ishizuka, Y.; Komori, J.; Shimano, T.; Nakano, S. The 2014 Eruption of Ontake Volcano, Central Japan. Volcanol. Soc. Japan 2015, 60, 411–415.
2. Maruyama, T. (2008). Large eddy simulation of turbulent flow around a windbreak. Journal of Wind Engineering and Industrial Aerodynamics 96, 1998–2006.
Acknowledgments: This research was funded by Integrated Program for Next Generation Volcano Research and Human Resource Development・Issue D: Development of volcanic disaster countermeasure technology・Sub-theme 2: “Development of real-time volcanic ash hazard evaluation method”.
Volcanic eruption products such as ash, ciders, hazardous gas and so on sometimes cause disasters. Volcanic ash harms crops, traffics, transportations, human health and so on. Flying ciders, lapilli and volcanic blocks often cause loss of lives and structures so as the eruption of Mt. Ontake in September 2014 causing 63 deaths and missing persons [1]. Accurate prediction of the product’s distribution is necessary for prevention and mitigation of the disaster. The distribution of flying products is affected by the air flow around the volcano, therefore the prediction of the flow field is essential for the prevention and mitigation of the volcanic disasters.
The trajectory of the volcanic smoke, ash and the flying product is directly affected by the wind flow, resulting in a distribution of the density of eruption products. The flow field around the volcano varies with the meteorological condition, the topography and the surface roughness. And fluctuation of the flow affects the distribution of the density.
2. Outline of Calculation
We designed a numerical simulation of wind flow around Sakurajima Volcano. The large eddy simulation using the Smagorinsky model was used for calculating the turbulent flow fields. The spatial averaging was conducted to the governing equation of the fluid and the effect of drag caused by the surface roughness such as plants and the buildings are added to the governing equations as a canopy model [2]. The curvilinear coordinate system was used for generating the topography. The meteorological condition was introduced as an inflow condition with wind velocity and temperature field obtained from the mesoscale numerical weather prediction model WRF. The eruption was expressed as a blowout of hot air and the effect of buoyancy was introduced by Boussinesq approximation. The volcanic ash was calculated as a diffusion of scalar density.
3. Calculated Results
Turbulent wind flow around Sakurajima volcano with eruption was simulated. The distribution of plants and buildings on the ground surface was obtained from the GIS data base and field survey. Space-time variation of wind velocity, temperature and ash density was obtained as shown in Figure 1.
4. Conclusions
Numerical method of turbulent flow field around a volcano with eruption was presented. The effect of surface roughness, topography, meteorological condition and eruption was reflected to the simulated turbulent wind fields.
Reference
1. Oikawa, T.; Yamaoka, K.; Yoshimoto, M.; Nakada, S.; Takeshita, Y.; Maeno, F.; Ishizuka, Y.; Komori, J.; Shimano, T.; Nakano, S. The 2014 Eruption of Ontake Volcano, Central Japan. Volcanol. Soc. Japan 2015, 60, 411–415.
2. Maruyama, T. (2008). Large eddy simulation of turbulent flow around a windbreak. Journal of Wind Engineering and Industrial Aerodynamics 96, 1998–2006.
Acknowledgments: This research was funded by Integrated Program for Next Generation Volcano Research and Human Resource Development・Issue D: Development of volcanic disaster countermeasure technology・Sub-theme 2: “Development of real-time volcanic ash hazard evaluation method”.