Alin A. Dobre

Computational Modeling of Arterial Blood Flow

Recently, there is a growing interest in developing numerical methods and tools to investigate the hemodynamics of the arterial flow, and to understand its influence on the transport of solutes (e.g., oxygen), nutrients, etc. As arteries morphology is complex and patient-related, medical data based reconstruction of the geometry may be utilized to generate realistic computational domains. The blood flow is then investigated by finite element method (FEM) for a range of flow parameters. The flow patterns thus obtained may be utilized for vascular surgery training, planning and intervention, to investigate atherosclerosis genesis, in drug targeting, etc.

Numerical simulation in electrical cardiometry

This study is concerned with the direct problem of Electro Cardiometry (ECM) technique, and the associated thoracic electrical bioimpedance (TEB). We present a mathematical model for the hemodynamic of the aorta, the change in the electrical conductivity of the blood, and the electrical field problem equivalent to the ECM procedure. Having in view that anatomy plays a key role in investigating the ECM-TEB problem we used a 3D computational domain produced by medical image based reconstruction techniques. The mathematical model is solved by numerical simulation in the finite element method (FEM) technique. Analytic formulae for the electrical conductivity of the blood are available, however, when investigating the hemodynamic of the aorta flow considering an anatomically realistic computational domain, these results are difficult (if possible) to use as such. To circumvent this difficulty we defined an equivalent conductivity based on analytic results, by averaging techniques that outline the sensitivity of TEB to the aorta blood flow dynamics. The work reported here addresses the direct problem of ECM-TEB, aiming at assessing the sensitivity of TEB to the flow parameters. Its solution opens the path to the inverse EMC-TEB problem, with the objective of deciphering the flow dynamics out of EMC-TEB experimental data.

The investigation of flow - Structural interaction in an arterial branching by numerical simulation

There is an outstanding growing interest in developing numerical methods and tools to investigate the hemodynamic of the arterial flow, and to understand its interaction with the anatomic structural system. As arteries morphology is complex and patient-related, medical data based reconstruction of the geometry may be utilized to generate realistic computational domains. Numerical methods and image-based geometry reconstruction have reached the stage where they may be utilized to investigate and predict the hemodynamic flows in arteries. In this paper we report numerical simulation results on arterial blood flow - vessel and muscular mass interaction. The flow patterns and the structural displacements thus obtained may be utilized for vascular surgery training, planning and intervention, to investigate atherosclerosis genesis, in drug targeting, etc.

Planning of renal tumor ablation aided by numerical modeling

This paper reports numerical simulation results on the radio frequency (RF) renal ablation procedure, using a simplified model for the kidney. The case study assumes that one of the extremities of the renal vein is affected by a small tumor (less than 3 cm in diameter) that has to be removed by heating it up above the physiological limit of viability. The local heating process is obtained using a four electrodes array, positioned by the targeted tumor. The kidney tissue is seen as a porous media and the associated hemodynamics is governed by Navier-Stokes momentum balance, for the large blood vessels and their first and second order ramifications, and Brinkman momentum balance, for the blood transfer between the renal arteries and veins, momentum balance.

High Temperature Superconductor dipolar magnet for high magnetic field generation - design and fabrication elements

The paper reports the design and realization of a dipolar superconducting electromagnet for high uniformity magnetic field generation, aimed for particle accelerators. The adopted solution for winding distribution is of cosine type. The HTS coils are executed from YBCO tape, 6 mm wide. The mathematical model and numerical, finite element (FEM) analysis was performed for model optimization. First, was addressed the magnetic field problem, as the main purpose of the HTS electromagnet is to provide for a highly uniform (10−3), high flux density magnetic field (∼2.5 T). The study is based on a three dimensional computational domain that was CAD-designed for the prototype. The numerical simulation results unveil the magnetic field, which is valuable in optimizing the electromagnet design and assessing its magnetic field fingerprint. The electrodynamic forces are of concern to the mechanical stability of the HTS winding, and numerical simulation is used to evaluate their spectrum and to predict the regions of higher concentration.

Sizing relations for an electromagnetic cantilever microactuator

This paper is concerned with the analytic solution, in the order of magnitude sense, of the mathematical models that describes the electokinetic and magnetic fields within an electromagnetic microactuator of cantilever type. The nondimensional form of the mathematical model is derived. To this aim, reference quantities are identified. Then the physical quantities and the mathematical model are scaled. It is assumed that the media are linear, and superposition is used to separate interacting magnetic fields produced by the permanent magnets and the electrical current carrying coil. This approach provides for simple, “back of an envelope” sizing relations that are useful in the first stages of design.