The influence of gas pore pressure in dense granular flows: numerical simulations versus experiments and implications for pyroclastic density currents

2021 ◽  
Vol 83 (11) ◽  
Author(s):  
Alvaro Aravena ◽  
Laurent Chupin ◽  
Thierry Dubois ◽  
Olivier Roche
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Granular Flows ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
Dense Granular Flows

scholarly journals New developments in the analysis of volcanic pyroclastic density currents through numerical simulations of multiphase flows

2012 ◽  
Vol 4 (1) ◽  
pp. 173-202 ◽  
Author(s):  
S. Lepore ◽  
C. Scarpati
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Gas Phase ◽  
Granular Flow ◽  
Granular Flows ◽  
Multiphase Model ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
High Concentration ◽  
Low Concentration

Abstract. A granular multiphase model has been used to evaluate the action of differently sized particles on the dynamics of fountains and associated pyroclastic density currents. The model takes into account the overall disequilibrium conditions between a gas phase and several solid phases, each characterized by its own physical properties. The dynamics of the granular flows has been simulated by adopting a Reynolds Average Navier-Stokes model for describing the turbulence effects. Numerical simulations have been carried out by using different values for the eruptive column temperature at the vent, solid particles frictional concentration, turbulent kinetic energy, and dissipation. The results obtained underline the importance of the multiphase nature of the model and characterize several disequilibrium effects. The low concentration (≤ 5 · 10–4) sectors lie in the upper part of the granular flow, above the fountain, and above the pyroclastic current tail and body as thermal plumes. The high concentration sectors, on the contrary, form the fountain and remain along the ground of the granular flow. Hence, pyroclastic density currents are assimilated to granular flows constituted by a low concentration suspension flowing above a high concentration basal layer (boundary layer), from the proximal regions to the distal ones. Interactions among solid, differently sized particles in the boundary layer of the granular flow are controlled by collisions between particles, whereas particles dispersal in the suspension is determined by the dragging of the gas phase. The simulations describe well the dynamics of a tractive boundary layer leading to the formation of stratified facies during eruptions having a different magnitude.

scholarly journals New developments in the analysis of column-collapse pyroclastic density currents through numerical simulations of multiphase flows

Solid Earth ◽  
2012 ◽  
Vol 3 (1) ◽  
pp. 161-173
Author(s):  
S. Lepore ◽  
C. Scarpati
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Gas Phase ◽  
Granular Flow ◽  
Granular Flows ◽  
Multiphase Model ◽  
Pyroclastic Density Currents ◽  
Density Currents ◽  
High Concentration ◽  
Low Concentration

Abstract. A granular multiphase model has been used to evaluate the action of differently sized particles on the dynamics of fountains and associated pyroclastic density currents. The model takes into account the overall disequilibrium conditions between a gas phase and several solid phases, each characterized by its own physical properties. The dynamics of the granular flows (fountains and pyroclastic density currents) has been simulated by adopting a Reynolds-averaged Navier-Stokes model for describing the turbulence effects. Numerical simulations have been carried out by using different values for the eruptive column temperature at the vent, solid particle frictional concentration, turbulent kinetic energy, and dissipation. The results obtained provide evidence of the multiphase nature of the model and describe several disequilibrium effects. The low concentration (≤5 × 10−4) zones lie in the upper part of the granular flow, above the fountain, and above the tail and body of pyroclastic density current as thermal plumes. The high concentration zones, on the contrary, lie in the fountain and at the base of the current. Hence, pyroclastic density currents are assimilated to granular flows constituted by a low concentration suspension flowing above a high concentration basal layer (boundary layer), from the proximal regions to the distal ones. Interactions among the solid particles in the boundary layer of the granular flow are controlled by collisions between particles, whereas the dispersal of particles in the suspension is determined by the dragging of the gas phase. The simulations describe well the dynamics of a tractive boundary layer leading to the formation of stratified facies during Strombolian to Plinian eruptions.

Effects of volcano profile on dilute pyroclastic density currents: Numerical simulations

Geology ◽  
2011 ◽  
Vol 39 (10) ◽  
pp. 947-950 ◽  
Author(s):  
Greg A. Valentine ◽  
Domenico M. Doronzo ◽  
Pierfrancesco Dellino ◽  
Marco D. de Tullio
Keyword(s):  
Numerical Simulations ◽  
Pyroclastic Density Currents ◽  
Density Currents
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