Date of Award

2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

First Advisor

Balachandar, Ram

Second Advisor

Barron, Ron

Keywords

Air entrainment, CFD, Free-surface flows, Multiphase flow, Turbulence

Rights

CC BY-NC-ND 4.0

Abstract

This dissertation deals with the computational study of free-surface flows with air entrainment. The aim of the study was to identify a suitable multiphase flow model that is capable of not only simulating the intricate flow physics but is also able to capture the free-surface deformations and predict the air entrainment at a reasonable computational cost. Finite volume based computations were performed using STAR-CCM+ commercial solver. The volume of fluid (VOF) multiphase model was used in the present study. First, a submerged hydraulic jump with an inlet Froude number F1 = 8.2 is simulated to determine the capabilities of the VOF multiphase model in capturing the free-surface deformations and other flow characteristics. The submerged hydraulic jump entrains lesser quantities of air and the free-surface deformations are not as abrupt as the classical hydraulic jump. Hence, this problem was chosen as a benchmark to validate the model. The VOF multiphase model was able to accurately capture the submerged hydraulic jump flow field. Proper orthogonal distribution (POD) analysis of the fluctuating velocity of the submerged hydraulic jump revealed the breakdown of large-scale structures into smaller-scale structures by the interaction of the roller and wall-jet flow, leading to the dissipation of energy.

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