This paper aims to clarify dynamical threshold in experimental, numerical, and theoretical manners for cavitation in water under a finite duration of tension. A once-through, non-recirculating, cavitation tunnel is constructed to run the tests. Within the test section, a cylinder is installed, behind which cavitation occurs, and once cavitated, water cannot return to the monitoring section. Cavitation threshold experiments are conducted in conditions controlled for flow velocity, pressure, and filtration degree of water. Conditions suitable for threshold tests are found in relation to Reynolds number and cavitation number. In parallel, LES-based CFD computations with three dimensional turbulent models are made to simulate water flows in the visualization section under experimental conditions, by which velocity distribution at the throat, pressure distribution before and after the throat, flow separation, and vortex formation downstream of the separation point are clarified. As an alternative approach, bubble dynamics analysis using Rayleigh-Plesset equation is conducted for conditions under which bubble nuclei grow according to CFD-based pressure histories, revealing that nuclei with O(1μm)-radius suddenly start to appear and grow at the separation point. Finally, dynamical cavitation threshold theory is successfully applied to predict nuclei growth, resulting in agreement with the bubble dynamics analysis.
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