Phase boundary estimation in two-phase flows with electrical impedance imaging technique

The visualization of two-phase flows can be regarded as the determination of the phase boundary. This paper deals with phase boundary estimation in two-phase flows with the electrical impedance imaging technique, where resistivity distribution is reconstructed based on the relationship between the predetermined excitations and the corresponding electrical responses. In most boundary estimation algorithms in EIT (Electrical Impedance Tomography), anomaly (i.e. bubble) boundaries can be expressed with truncated Fourier series and the unknown coefficients are estimated with proper inverse algorithms. Furthermore, the number of anomalies is assumed to be available a priori. The prior knowledge on the number of anomalies may be unavailable in some cases, and we need to determine the number of anomalies with other methods. This paper presents an algorithm for the boundary estimation in EIT using the prior information from the conventional Newton-Raphson method. Although Newton-Raphson method generates so poor spatial resolution that the anomaly boundaries are hardly reconstructed even after a few iterations, it can give some information on the object to be imaged such as the number of anomalies, their sizes and locations, as long as the anomalies are big enough. Some numerical experiments indicate that the Newton-Raphson method can be used as a good predictor of the unknown boundaries and the proposed boundary discrimination algorithm has a good performance.