Uncertainty assessment of cavity profile reconstructed by outward-ECT based on parameter bootstrap method and CFD-EMF simulation

Outward electrical capacitance tomography (Outward-ECT) provides a powerful method for monitoring the cavity profiles on the exterior of axisymmetric bodies. However, comprehensive quantitative analyses of attached cavities based on Outward-ECT measurements are still lacking. This study introduces a Monte Carlo parameter bootstrap method that quantifies the uncertainty of the reconstructed cavity profile using a posteriori means and standard deviations of bootstrap samples. Additionally, a coupled computational fluid dynamics and electromagnetic field (CFD-EMF) simulation framework is proposed to correct axial offset errors arising from the fringe effects of Outward-ECT. Water entry experiments were conducted, and high-speed camera images served as references to validate the proposed methodology. Experimental results demonstrate that the maximum uncertainty in the relative cavity radius measured by Outward-ECT during vertical water entry is 0.0475, corresponding to an actual deviation of 1.43 mm. Upon correction of axial offset error, the estimated relative radius from Outward-ECT closely matches the reference radius, illustrating the importance of correcting axial offset errors when monitoring cavity profiles using single-plane Outward-ECT.