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The Volume of Fluid ( VOF ) method is employed to track the melt pool free surfaces , and enthalpy-porosity method is used to model the solid-liquid phase change .
 Volume of Fluid, VOF, melt pool, free surfaces, model, phase
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 Volume of Fluid, VOF, melt pool, free surfaces, model, phase