A Separate Effect Facility (SEF-POOL) was designed to measure the time-averaged momentum induced by steam injection into a subcooled water pool. Recent analysis of large-scale pool data has shown that the turbulence generated by the steam injection affects not only velocity field in the vicinity of the steam injection point but also integral pool behavior (thermal mixing and stratification). Unfortunately, the application of existing techniques for the velocity field measurements (such as Particle Image Velocimetry) is difficult due to presence of small gas bubbles and significant temperature gradients in the liquid. In this paper we introduce an experimental approach to quantification of the velocity field using Bubble based Particle Tracking Velocimetry (Bub-PTV) in which the streamwise velocity is inferred by stereoscopic tracking of air bubbles entrained by the flow. This paper presents the development of in-house code for bubble tracking and preliminary results obtained from the tests using water injection into a water pool. These water injection tests are intended to verify the setup of the experiment (e.g. air generating system, stereo cameras) and provide databases for code development and validation. The results are also compared with Computational Fluid Dynamics (CFD) simulations performed in ANSYS Fluent, and good agreement was achieved. The experimental measurements suggest that the proposed approach can provide a 3D velocity field measurement of the jet. Moreover, it indicates the potential of Bub-PTV as a reliable technique for measuring downstream axial velocity fields induced by steam injection.

The time-averaged Effective Momentum Source (EMS) induced by steam injection into a subcooled water pool was measured in a Separate Effect Facility (SEF-POOL) under a wide range of injection conditions. Post-test simulations of large-scale pool experiments conducted in PANDA and PPOOLEX facilities indicate that diffusion of the momentum is another important factor that determines the downstream momentum transport and dynamics of the stratified layer. Thereby, an experimental quantification approach was introduced to measure the streamwise velocity profiles induced by steam injection. It is achieved by using Bubble based Particle Tracking Velocimetry (Bub-PTV) where the velocity is inferred by stereoscopic tracking of the injected air bubbles. In the previous work, we validated the approach using tests with water injection. In this paper, we discuss Bub-PTV application to steam injection tests. The Bub-PTV code was further developed to improve the performance of bubble detection under the steam injection conditions. The momentum induced by steam injection diffuses much faster compared to the single-phase liquid jet injection. We demonstrate that, in the far field where steam has condensed completely, the jet can be simulated using a single-phase solver with the Effective Heat and Momentum sources (EHS/EMS) models along with an additional turbulence source term to account for the turbulence generated in the process of steam condensation. Good agreement can be achieved on the downstream velocity profiles if the added turbulence source is properly calibrated.