Dynamical Phase-Change Phenomena

Matter on earth exists mostly in three different phases of solid, liquid, and gas. With extreme amounts of energy, temperature, or pressure, a matter can be changed between the phases. Six different types of phase-change phenomena are possible: freezing (the substance changes from a liquid to a solid), melting (solid to liquid), condensation (gas to liquid), vaporization (liquid to gas), sublimation (solid to gas), and desublimation (gas to solid). Another form of phase change which will be discussed here is the wetting or dewetting transitions of a superhydrophobic surface, in which the phase residing within the surface structure switches between vapor and liquid. Phase transition phenomena frequently occur in our daily life; examples include: a ``liquid'' to ``solid'' transition when cars decrease their distance at a traffic light, solidification of liquids droplets during winter months, and the dancing of droplets on a non-sticking pan. In this dissertation we will address seven different phase-change problems occurring in nature. We unveil completely new forms of phase-change phenomena that exhibit rich physical behavior. For example, during traffic flow, drivers keep a large distance from the vehicle in front of them to ensure safe driving. When vehicles come to a stop, for example at a red light, drivers voluntarily induce a ``phase transition'' from this ``liquid phase'' to a close-packed ``solid phase''. This phase transition is motivated by the intuition that traveling as far as possible before stopping will minimize the overall travel time. However, we are going to investigate this phase-change process and show that this long standing intuition is wrong. Phase-change of solidification will be discussed for different problems. Moreover, the complex physics of oil as it wicks up sheets of frost and freezing of bubble unveil completely new forms of multiphase flows that exhibit rich physical behavior. Finally, the ``Cassie'' to ``Wenzel'' transition will be investigated for layered nano-textured surfaces. These phenomena will be modeled using thermodynamics and fluid mechanics equations.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Engineering Mechanics

Department dc:contributor.department

Engineering Science and Mechanics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2019

Author dc:creator

• Ahmadi, Seyedfarzad

Chair dc:contributor.committeechair

• Boreyko, Jonathan B.

Committee members dc:contributor.committeemember

• Jung, Sunghwan
• Yue, Pengtao
• Abaid, Nicole
• Ragab, Saad A.

• traffic flow
• superhydrophobic
• anti-frosting
• anti-icing
• bubbles

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:20997

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/99420