A coupled solid–fluid method for modelling subduction

Abstract\n We present a novel dynamic approach for solid/fluid coupling by joining two different \nnumerical methods: Boundary Element Method (BEM) and Finite Element \nMethod (FEM). FEM results describe the thermo-mechanical evolution of the solid \nwhile the fluid is solved with the BEM. The bidirectional feedback between the two \ndomains evolves along a Lagrangian interface where the FEM domain is embedded \ninside the BEM domain. The feedback between the two codes is based on the calculation \nof a specific drag tensor for each boundary/finite element. The approach \nis presented here to solve the complex problem of the descent of a cold subducting \noceanic plate into a hot fluid like mantle. The coupling technique is shown \nto maintain the proper energy dissipation caused by the important secondary induced \nmantle flow induced by the lateral migrating of the subducting plate. We \nshow how the method can be successfully applied for modelling the feedback between \ndeformation of the oceanic plate and the induced mantle flow. We find that \nthe mantle flow drag is singular at the edge of the retreating plate causing a distinct \nhook shape. In Nature such hooks can be observed at the northern end of the Tonga \ntrench and at the southern South-American trench perimeter.