A computational model is developed to simulate the impact dynamics of a droplet on solid substrates with the purpose of predicting the droplet spreading characteristics over time. Previous studies focused on finding relations between the impact parameters and outcome dynamics. A modified approach like the one used in this project revolves around modeling the moving contact lines at the interface in a multiphase flow environment. Focusing on research from an aircraft de-icing point of view, this study is considered a prerequisite in understanding the physics of droplet impact. The primary focus is on extending the application to incorporate super-cooled environments. Development of the model involved the use of the Volume-of-Fluid function coupled with the High-Resolution Interface Capturing scheme to model the moving contact line. The evolution of the moving contact line is modeled with contact angles as their inputs to understand the effect of the surface tension forces. Contact angle modeling is based on the Blended-Kistler method, which captures the contact angle evolution based on the surface tension and capillary number. Preliminary validation performed on the model proves its effectiveness in accurately simulating the impact behavior when compared to the literature, where the spread diameter and height agree well with experiments. The validated model is also compared to the in-house experiments performed at the Cavitation and Multiphase flow laboratory using different substrate materials. The substrates each show unique behavior - Impact on Glass results in the droplet depositing on the surface. Aluminum results in a full rebound and PET-G, results in a drop ejection. Based on inputs from the experiments - contact angles, spread diameter, and the maximum spread $beta$, show good agreement in comparison to the literature. / Master of Science / Computational model developed to simulate the impact dynamics of the droplet on solid surfaces, which predicts the evolution of the droplet over time in order to analyze the effect of the surface and properties of the fluid on the behavior of the droplet on impact. Focusing on research from an aircraft de-icing point of view, this study is considered a pre-requisite in understanding the physics of droplet impact, with potential scope in extending the simulation to applications at temperatures lower than $0^{circ}$ C. A model developed with the help of basic governing equations in fluid mechanics helps capture the effect of interactions between different physical states. The angle at which the droplet interacts with the surface (Contact Angle) and the diameter evolution (d/D) help us understand the effectiveness of the model to simulate droplet impact. Preliminary validation of the model is performed with respect to the literature where the droplet diameter evolution and the height variation match well with the experiments, which was the major criterion in determining the accuracy of the model. This model is compared to the in-house experiments performed at the Cavitation and Multiphase flow laboratory on different surfaces such as Glass, Aluminum, and Plastic (PET-G). The surfaces each show unique behavior with impact on Glass having the droplet deposit on the surface, aluminum resulting in the droplet bouncing after hitting the surface, and PET-G resulting in a small droplet being ejected from the bigger droplet which eventually deposits on the surface. Conclusions from the comparison between the experiments and the numerical simulation show how the model is effective in capturing the impact behavior on surfaces like glass in comparison to surfaces like Aluminum in this case that repels water.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113599 |
| Date | 31 January 2023 |
| Creators | Saravanan Manikkam, Pratulya Rajan |
| Contributors | Aerospace and Ocean Engineering, Coutier-Delgosha, Olivier, Paterson, Eric G., Lowe, K. Todd |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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