16:00 〜 16:15
[MIS01-02] 塑性的な表皮を伴う溶岩流の粒子法シミュレーション
キーワード：パホイホイ溶岩、塑性的な表皮、非ニュートン流体、固液相変化、数値シミュレーション、SPH法
Characteristic phenomenon in lava flows, the formation of thin plastic skin by surface cooling, was numerically simulated successfully using the Smoothed Particle Hydrodynamics (SPH) method. This specific phenomenon may affect the extent where lava flows. Therefore, it is indispensable to elucidate and incorporate the phenomenon into models to accurately predict areas which lava strikes.
In order to simulate the formation of thin plastic skin by surface cooling, the model considers for temperature-dependent viscosity. The skin was treated as a low-temperature and high-viscosity region. In addition, an apparent viscosity model was introduced to simulate Bingham fluid behavior, in which apparent viscosity changes depended on strain rates. Using this model, the process of lava flowing on an inclined plate with formation of surface skin was simulated. Due to computational constraints, the viscosity coefficient was adjusted to 1/100 of its original value, with upper and lower limits set in the simulation. The following outcomes were observed in the simulations:
1. Rapid deceleration was observed by the introduction of the apparent viscosity model. In addition, the process was identified in which the apparent viscosity increased as the flow velocity decreased, and then the flow velocity further decreased. Finally, the process led the flow to stop. This process replicated the behavior of Bingham fluids qualitatively. Comparisons with Newtonian fluids confirmed that Bingham behavior significantly influenced lava flow velocity and distance.
2. The model successfully simulated the formation of thin skin (low-temperature and high-viscosity regions) observed on the surface of actual lava flow, by considering the temperature-dependent viscosity. Comparison with simulations without skin formations revealed that the skin suppressed the flow velocity. This is a qualitative replication of the flow suppression effect of the skin in actual lava flow. The simulation results confirmed that the formation of the skin affects the velocity and distance of lava flow. The suppression effect of the skin was also confirmed to influence the appearance of the Bingham behavior described above.
In summary, this model successfully simulated the non-Newtonian behavior of lava as a Bingham fluid, as well as the flow suppression effect of surface skin. The results indicated that Bingham behavior and the suppression effect of the skin have a significant impact on the flow distance. These findings emphasize the necessity of consideration of both non-Newtonian behavior and surface skin formation for accurate predictions of lava flow behavior.
In order to simulate the formation of thin plastic skin by surface cooling, the model considers for temperature-dependent viscosity. The skin was treated as a low-temperature and high-viscosity region. In addition, an apparent viscosity model was introduced to simulate Bingham fluid behavior, in which apparent viscosity changes depended on strain rates. Using this model, the process of lava flowing on an inclined plate with formation of surface skin was simulated. Due to computational constraints, the viscosity coefficient was adjusted to 1/100 of its original value, with upper and lower limits set in the simulation. The following outcomes were observed in the simulations:
1. Rapid deceleration was observed by the introduction of the apparent viscosity model. In addition, the process was identified in which the apparent viscosity increased as the flow velocity decreased, and then the flow velocity further decreased. Finally, the process led the flow to stop. This process replicated the behavior of Bingham fluids qualitatively. Comparisons with Newtonian fluids confirmed that Bingham behavior significantly influenced lava flow velocity and distance.
2. The model successfully simulated the formation of thin skin (low-temperature and high-viscosity regions) observed on the surface of actual lava flow, by considering the temperature-dependent viscosity. Comparison with simulations without skin formations revealed that the skin suppressed the flow velocity. This is a qualitative replication of the flow suppression effect of the skin in actual lava flow. The simulation results confirmed that the formation of the skin affects the velocity and distance of lava flow. The suppression effect of the skin was also confirmed to influence the appearance of the Bingham behavior described above.
In summary, this model successfully simulated the non-Newtonian behavior of lava as a Bingham fluid, as well as the flow suppression effect of surface skin. The results indicated that Bingham behavior and the suppression effect of the skin have a significant impact on the flow distance. These findings emphasize the necessity of consideration of both non-Newtonian behavior and surface skin formation for accurate predictions of lava flow behavior.