Interfacial Area Transport Equation for Bubbly to Cap-bubbly Transition Flows
Open Access
- Author:
- Worosz, Theodore Stanley
- Graduate Program:
- Nuclear Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 01, 2015
- Committee Members:
- Seungjin Kim, Dissertation Advisor/Co-Advisor
Seungjin Kim, Committee Chair/Co-Chair
Fan Bill B Cheung, Committee Member
Kostadin Nikolov Ivanov, Committee Member
Francesco Costanzo, Committee Member
Kevin Hogan, Special Member - Keywords:
- two-phase flow
interfacial area concentration
two-group interfacial area transport
multi-sensor conductivity probe
cap-bubbl - Abstract:
- To fully realize the benefit of the two-group interfacial area transport equation (IATE) as a constitutive model for the interfacial area concentration in the two-fluid model, it is imperative that models be developed to dynamically transition from one-group to two-group flows. With this in mind, the two-group IATE is derived in detail to establish new expansion source terms that correctly account for the effects of intergroup bubble transport. In addition to this theoretical effort, the state-of-the-art four-sensor conductivity probe is used to establish a reliable experimental database of local two-phase flow parameters to characterize one-group to two-group transition flows and to support model development. The experiments are performed in vertical-upward air-water two-phase flow in a 5.08cm pipe. Additionally, the local conductivity probe is improved through systematic studies into: 1) signal “ghosting” electrical interference among probe sensors, 2) sampling frequency sensitivity, 3) measurement duration sensitivity, and 4) probe sensor orientation. Wake-dominated bubble transport characterizes the transition from one-group to two-group flows. Therefore, the necessary intergroup and intragroup wake entrainment source terms that are required for two-group interfacial area transport in transition flows are developed. Furthermore, an approach is developed to initiate the shearing-off source and reduce the one-group interaction mechanisms as an established two-group flow develops. The new interfacial area transport model for one-group to two-group transition flows is evaluated against the experimental database. The model accurately captures the exchange of void fraction and interfacial area concentration between group-I and group-II in transition flows. Overall, the group-I void fraction and interfacial area concentration are predicted within ±6% and ±4%, respectively, of the experimental data. The group-II void fraction and interfacial area concentration are predicted within ±9% and ±11%, respectively, of the experimental data.