title: Time-resolved fast-neutron radiography of air-water two-phase flows in a rectangular channel by an improved detection system.
abstract: In a previous work, we have demonstrated the feasibility of high-frame-rate, fast-neutron radiography of generic air-water two-phase flows in a 1.5 cm thick, rectangular flow channel. The experiments have been carried out at the high-intensity, white-beam facility of the Physikalisch-Technische Bundesanstalt, Germany, using an multi-frame, time-resolved detector developed for fast neutron resonance radiography. The results were however not fully optimal and therefore we have decided to modify the detector and optimize it for the given application, which is described in the present work. Furthermore, we managed to improve the image post-processing methodology and the noise suppression. Using the tailored detector and the improved post-processing, significant increase in the image quality and an order of magnitude lower exposure times, down to 3.33 ms, have been achieved with minimized motion artifacts. Similar to the previous study, different two-phase flow regimes such as bubbly slug and churn flows have been examined. The enhanced imaging quality enables an improved prediction of two-phase flow parameters like the instantaneous volumetric gas fraction, bubble size, and bubble velocities. Instantaneous velocity fields around the gas enclosures can also be more robustly predicted using optical flow methods as previously.
authors.affiliation: Paul Scherrer Institute, PSI Villigen 5232, Switzerland.
authors.forename: Robert
authors.initials: R
authors.lastname: Zboray
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 38116, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Dangendorf
authors.affiliation: Soreq NRC, Yavne 81800, Israel.
authors.forename: Ilan
authors.initials: I
authors.lastname: Mor
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 38116, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bromberger
authors.affiliation: Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 38116, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Tittelmeier