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EAS Doctoral Proposal Defense by Kartik Gupta
Topic:
Computational investigation and theoretical modeling of water entry of cylinders at various nose curvatures, tilt angles, and axial rotations
Abstract:
Water entry—the process in which a solid body impacts and penetrates the air–water interface—represents a complex fluid–structure interaction (FSI) phenomenon with applications such as seaplane landings, capsule splashdowns, and projectile entries. This process involves several interconnected phases, including impact, cavity formation, closure (pinch- off), and jet emergence, each governed by transient pressure fields and highly unsteady flow interactions. The geometry of the impacting body plays a pivotal role: convex noses induce smoother flow and shallower cavities; concave noses tend to trap air and delay closure, while flat noses generate strong splashes and deeper cavities. The forces generated during this process—particularly the added mass arising from fluid acceleration induced by the solid’s motion—govern the object’s dynamics and structural response. Accurate quantification of added mass is therefore crucial for predicting impact forces in many critical applications. While most existing studies have elucidated many aspects of symmetric, vertical water entry, real-world scenarios often exhibit asymmetry caused by oblique impact angles or axial rotation. These effects lead to complex cavity dynamics and unsteady hydrodynamic forces that conventional analytical models for predicting added mass fail to accurately capture.
This PhD research proposes a novel method for quantifying added mass directly from time-resolved fluid velocity fields, applicable to both computational and experimental analyses without relying on force sensors or accelerometers. The research approach relies on computational simulations performed by our in-house multiphase flow solver, which is based on the Volume-of-Fluid method and uses a consistent mass and momentum transport scheme, allowing for accurate simulations of high-density ratio flows. The solver uses the fast-fictitious domain method for modeling FSI. In these large-scale simulations, impact velocity, nose-curvature, tilt angle and axial rotation are varied. Post processing the simulation results, the impact of the above parameters on water entry, including air cavity formation and closure (pinch-off), liquid-jet ejection, air entrapment, as well as added-mass and impact coefficient are quantified. Finally, Aristoff et al.’s theory for spheres is extended to the water entry of cylinders with various nose curvatures to predict the pinch-off event.
Advisor: Dr. Mehdi Raessi, Department of Mechanical Engineering
Committee members:
- Dr. Banafsheh Seyed-Aghazadeh, Department of Mechanical Engineering
- Dr. Geoffrey Cowles, Dept. of Fisheries Oceanography, SMAST
- Dr. Alfa Heryudono, Department of Mathematics
Note: All EAS Students are encouraged to attend.
SENG 107
Dr. Mehdi Raessi
mraessi@umassd.edu