The porous media theory applied to radiofrequency catheter ablation

Purpose Recently, the porous media theory has been successively proposed for many bioengineering applications. The purpose of this paper is to analyze if the porous media theory can be applied to model radiofrequency (RF) cardiac ablation. Design/methodology/approach Blood flow, catheter and tissue are modeled. The latter is further divided into a fluid and a solid phase, and porous media equations are used to model them. The heat source term is modeled using the Laplace equation, and the finite element method is used to solve the governing equations under the appropriate boundary conditions and closure coefficients. Findings After validation with available literature data, results are shown for different velocities and applied voltages to understand how these parameters affect temperature fields (and necrotic regions). Research limitations/implications The model might require further validation with experiments under different conditions after comparisons with available literature. However, this might not be possible due to the experimental complexity. Practical implications The improvement in predictions from the model might help the final user, i.e. the surgeon, who uses cardiac ablation to treat arrhythmia. Originality/value This is the first time that the porous media theory is applied to RF cardiac ablation. The robustness of the model, in which many variables are taken into account, makes it suitable to better predict temperature fields, and damaged regions, during RF cardiac ablation treatments.

3D simulation of transversely isotropic laminated composites in RTM using poromechanics

In the present paper we are trying to establish a 3D simulation framework for Resin Transfer Molding for a laminated preform using the already developed porous media theory for composite materials process simulation purposes. The aim here is to implement the process phenomena, such as coupling of sub-processes that are happening simultaneously, in a full 3D description of the problem. For this purpose, an 8-node solid shell element is employed to be able to handle complex 3D stress-strain states. The development is exemplified considering RTM process where the main focus of the modeling will be on the flow advancement into fiber preform and flow front capturing. To this end, the theory of two-phase porous media is used along with assuming hyper-elastic material response for the fiber bed to formulate the problem. A finite element formulation and implementation of the two-phase problem is developed, and the results are presented accordingly.

A model for capillary hysteresis loops in unsaturated porous media theory

In this paper, we show how very relevant mathematical works of P.I. Plotnikov, publicized by L.C. Evans and M. Portilheiro, can be used to model the effects of cyclic hysteresis phenomena for flows in unsaturated porous media. We draw particular attention to the example of a model for water–air flows, simplified for purposes of illustration. First, an unstable “spinodal” interval is artificially introduced. Then S.L. Sobolev’s method of dynamic regularization allows associating with the continuity equations additional information in the form of entropy type inequalities. The asymptotic limits of viscous approximate solutions generate effects of irreversibility and the expected clockwise hysteresis loop.