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International Society for Industrial Process Tomography

3rd World Congress on Industrial Process Tomography

Estimating Shapes and Free Surfaces with Electrical Impedance Tomography


O-P Tossavainen and M Vauhkonen


Department of Applied Physics, University of Kuopio, P.O. Box 1627, 70211 KUOPIO, Finland, Email: Marko.Vauhkonen@uku.fi


ABSTRACT


Electrical impedance tomography (EIT) is a diffuse imaging modality in which the resistivity distribution inside the object is estimated based on electrical measurements made on the boundary. In the image reconstruction process the geometry of the object is assumed to be known. However, the geometry is unknown in many cases, for example in medical applications, in which the human body on which the measurement electrodes are attached, is unknown unless some other imaging modality is used for receiving the shape. In industrial applications, such as imaging of stirrer vessel for detecting air distribution or detecting large air bubbles in pipelines, the interface between the liquid and air is unknown and may be of interest. Within the domain there may also exist “voids” having either zero conductivity or infinite conductivity and we might be interested in detecting the shapes and locations of the voids. In this paper two approaches for free surface (interface between air and liquid) estimation are proposed. The approach taken here is based on the idea used in the shape optimization problems in which the unknown shape is parametrized using the mesh nodes as parameters or defining new “design variables”. In this paper, these design variables are control points of a Bézier curve that defines the shape of the surface. Theory and results of computer simulations of free surface estimation with nodal and Bézier design variable approaches will be shown.


Keywords EIT, Finite element method, Shape optimization, Design variables, Bézier curve

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