Interface-Sensitive Electrical Capacitance-Ratio Tomography for Supercavity Profile Reconstruction in Open Domain

Subtle disturbances of supercavity profile can destabilize high-speed underwater vehicles, potentially causing severe accidents. Existing methods struggle to online monitor the supercavity profile on the outer surface of the axisymmetric gyratory body of an underwater vehicle. Electrical capacitance tomography (ECT), with its soft-field characteristics, offers a promising solution, but traditional approaches face limitations on reconstructing supercavity profile with high sensitivity and resolution due to the large permittivity contrast between water and air. This study proposes an Outward Electrical Capacitance Ratio Tomography (OECRT) framework for the monitoring of supercavity profile, where it is theoretically proved that the specified inter-electrode capacitance ratio is only sensitive to air-water interface irrespective of the dielectric contrast. Unlike traditional closed-domain ECT, OECRT establishes a direct bijective function between the boundary inter-electrode capacitance ratios and the open-domain supercavity profile. Results of water-entry experiments demonstrate that OECRT outperforms the conventional methods in both the sensitivity to phase interface changes and spatial and temporal resolutions. The proposed OECRT method is a promising alternative to the traditional closed-domain ECT methods, especially in the cases where there exists large dielectric contrast between the target and background media or open-domain imaging is required.