scholarly journals Utilization of Nonequilibrium Phase Change Approach to Analyze the Nonisothermal Multiphase Flow in Shallow Subsurface Soils

2020 ◽  
Vol 56 (10) ◽  
Author(s):  
Mohammadreza Mir Tamizdoust ◽  
Omid Ghasemi‐Fare
Keyword(s):  
Multiphase Flow ◽  
Phase Change ◽  
Shallow Subsurface ◽  
Nonequilibrium Phase

scholarly journals Multiphase Flow and Phase Change in Microgravity: Fundamental Research and Strategic Research for Exploration of Space

2003 ◽  
Author(s):  
Bhim S. Singh
Keyword(s):  
Multiphase Flow ◽  
Phase Change ◽  
Space Flight ◽  
Closed Loop ◽  
Life Support ◽  
Support Systems ◽  
Pool Boiling ◽  
Microgravity Environment ◽  
Strategic Research ◽  
Fundamental Research

NASA is preparing to undertake science-driven exploration missions. The NASA Exploration Team’s vision is a cascade of stepping stones. The stepping-stone will build the technical capabilities needed for each step with multi-use technologies and capabilities. An Agency-wide technology investment and development program is necessary to implement the vision. The NASA Exploration Team has identified a number of areas where significant advances are needed to overcome all engineering and medical barriers to the expansion of human space exploration beyond low-Earth orbit. Closed-loop life support systems and advanced propulsion and power technologies are among the areas requiring significant advances from the current state-of-the-art. Studies conducted by the National Academy of Science’s National Research Council and Workshops organized by NASA have shown that multiphase flow and phase change play a crucial role in many of these advanced technology concepts. Lack of understanding of multiphase flow, phase change, and interfacial phenomena in the microgravity environment has been a major hurdle. An understanding of multiphase flow and phase change in microgravity is, therefore, critical to advancing many technologies needed. Recognizing this, the Office of Biological and Physical Research (OBPR) has initiated a strategic research thrust to augment the ongoing fundamental research in fluid physics and transport phenomena discipline with research especially aimed at understanding key multiphase flow related issues in propulsion, power, thermal control, and closed-loop advanced life support systems. A plan for integrated theoretical and experimental research that has the highest probability of providing data, predictive tools, and models needed by the systems developers to incorporate highly promising multiphase-based technologies is currently in preparation. This plan is being developed with inputs from scientific community, NASA mission planners and industry personnel. The fundamental research in multiphase flow and phase change in microgravity is aimed at developing better mechanistic understanding of pool boiling and ascertaining the effects of gravity on heat transfer and the critical heat flux. Space flight experiments conducted in space have shown that nucleate pool boiling can be sustained under certain conditions in the microgravity environment. New space flight experiments are being developed to provide more quantitative information on pool boiling in microgravity. Ground-based investigations are also being conducted to develop mechanistic models for flow and pool boiling. An overview of the research plan and roadmap for the strategic research in multiphase flow and phase change as well as research findings from the ongoing program will be presented.

scholarly journals A Novel 2D Model for Freezing Phase Change Simulation during Cryogenic Fracturing Considering Nucleation Characteristics

2020 ◽  
Vol 10 (9) ◽  
pp. 3308
Author(s):  
Chengyu Huang ◽  
Wenhua Wang ◽  
Weizhong Li
Keyword(s):  
Multiphase Flow ◽  
Phase Change ◽  
Heterogeneous Nucleation ◽  
Initial Distribution ◽  
Freezing Process ◽  
Computational Domain ◽  
Comparison Results ◽  
Fracturing Process ◽  
Cryogenic Fracturing ◽  
Ice Phase

A 2D computational fluid dynamics (CFD) model in consideration of nucleation characteristics (homogeneous/heterogeneous nucleation) using the volume of fluid (VOF) method and Lee model was proposed. The model was used to predict the process of a multiphase flow accompanied by freezing phase change during cryogenic fracturing. In this model, nucleation characteristic (homogeneous and heterogeneous nucleation) during the freezing process and the influence of the formed ice phase on the flowing behavior was considered. Validation of the model was done by comparing its simulation results to Neumann solutions for classical Stefan problem. The comparison results show that the numerical results are well consistent with the theoretical solution. The maximum relative differences are less than 7%. The process of multiphase flow accompanied by the freezing of water was then simulated with the proposed model. Furthermore, the transient formation and growth of ice as well as the evolution of temperature distribution in the computational domain was studied. Results show that the proposed method can better consider the difference between homogeneous nucleation in the fluid domain and heterogeneous nucleation on the wall boundary. Finally, the main influence factors such as the flow velocity and initial distribution of ice phase on the fracturing process were discussed. It indicates that the method enable to simulate the growth of ice on the wall and its effect on the flow of multiphase fluid.

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