Alexandre M. Roma

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The Immersed Boundary Method is a versatile tool for the investigation of flow-structure interaction. In a large number of applications, the immersed boundaries or structures are very stiff and strong tangential forces on these interfaces induce a well-known, severe time-step restriction for explicit discretizations. This excessive stability constraint can(More)
We present an efficient numerical methodology for the 3D computation of incompressible multi-phase flows described by conservative phase field models. We focus here on the case of density matched fluids with different viscosity (Model H). The numerical method employs adaptive mesh refinements (AMR) in concert with an efficient semi-implicit time(More)
We present a variable time step, fully adaptive in space, hybrid method for the accurate simulation of incompressible two-phase flows in the presence of surface tension in two dimensions. The method is based on the hybrid level set/front-tracking approach proposed in [H.D. Ceniceros and A. M. Roma, J. Comput. Phys., 205, 391400, 2005 ]. Geometric,(More)
We present a nonstiff, fully adaptive mesh refinement-based method for the CahnHilliard equation. The method is based on a semi-implicit splitting, in which linear leading order terms are extracted and discretized implicitly, combined with a robust adaptive spatial discretization. The fully discretized equation is written as a system which is efficiently(More)
We present a methodology to perform efficiently micromagnetics simulations which combines an unconditionally stable, finite differences scheme with an adaptive mesh refinement technique. Enhanced accuracy is attained by covering locally special regions of the domain with a sequence of nested, progressively finer rectangular grid patches which dynamically(More)
We present a novel methodology for incompressible multi-phase flow simulations in which the fluid indicator is a local signed distance (level set) function, and FrontTracking is used to evaluate accurately geometric interfacial quantities and forces. Employing ideas from Computational Geometry , we propose a procedure in which the level set function is(More)
In this paper a simulation model is presented for the Direct Numerical simulation (DNS) of multiphase flow. This method combines the Volume of fluid model and Immersed Boundary method in order to investigate water-oil flow-pattern. The simulations were carried out on structured cartesian adaptive mesh refinement (SAMR), where the the Immersed Boundary(More)
We present a numerical investigation of the three-dimensional coarsening dynamics of a nematic liquid crystal-isotropic fluid mixture using a conserved phase field model. The model is a coupled system for a generalized CahnHilliard equation for the order parameter φ, related to the volume fraction of the nematic component, and a simplified de Gennes-Prost(More)
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