Date of Award:

12-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Committee Chair(s)

Som Dutta

Committee

Som Dutta

Committee

Barton Smith

Committee

Jia Zhao

Abstract

In this research, we study the behavior of flow around a cylinder in the presence of stable stratification, which refers to variations in density throughout the fluid. This phenomenon is observed in natural and industrial settings. We use computer simulations to analyze how stratification affects the flow patterns created by the cylinder. Specifically, we investigate situations where the stratification is perpendicular to the flow direction, and the wake exhibits two-dimensional characteristics. We use spectral-element method based computational fluids dynamics to simulate the phenomena. During the simulations, we vary two important parameters: the Densimetric Froude Number (Fr) and the Reynolds Number (Re). Fr characterizes the strength of the stratification, while Re represents the flow’s intensity/speed based on the cylinder’s size. We consider a wide range of Fr values from very small to infinity (high density gradient to no change in density), and Re values from 10 to 180. By analyzing the simulations, we measure the drag and lift forces acting on the cylinder, and calculate Strouhal Number of the wake describing the frequency of vortex shedding (the formation and shedding of vortices behind the cylinder). To further classify and understand the flow structures, we employ a technique called Dynamic Mode Decomposition (DMD). DMD identifies the most dominant flow patterns present, with a focus on the shedding rate of vortices when they are observed. Overall, we aim to explore how different flow structures are influenced by the presence of stratification, and how they are suppressed or formed depending on the values of Reynolds Number and Froude Number. This research helps us gain insights into the effects of stratification on flow behavior around cylinders in two-dimensional, stratified flows.

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Creative Commons Attribution 4.0 License
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