Date of Award

Summer 9-2019

Access Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Vladimir V. Golubev

First Committee Member

William Engblom

Second Committee Member

Anastasios S. Lyrintzis

Third Committee Member

R.R. Mankbadi

Abstract

The purpose of this dissertation is to analyze the momentum source model, for generating synthetic vortical disturbance field in numerical simulations of unsteady fluid-structure interactions, access limitations of this approach, to find requirements for the computational domain, space and time resolution, and apply this model to investigate selected physical problems. For this reason a comprehensive parametric study of volume-force based method of generating spectral synthetic turbulence inside the computational domain is conducted first. The method is then extended to synthesize turbulence with arbitrary energy spectrum. The synthetic turbulence is generated through momentum source terms in Navier-Stokes equations, and the developed numerical procedure is shown to reproduce any desired energy spectrum. Additionally, the approach is extended to be applicable to boundary layer type of flows. Then, selected applications of the momentum source model are considered including: gust-airfoil unsteady interactions, turbulence-airfoil unsteady interactions, Analysis of the turbulence effect on acoustic radiation of a novel airfoil design with an embedded cross-ow fan, the effect of turbulence intensity on wake vortex evolution.

In particular the effects of oblique vortical gust modes on airfoil unsteady aerodynamic and acoustic responses due to its interaction with an impinging 3D time-harmonic gust and turbulence are addressed first. Several analytical gust-airfoil interaction models are reviewed and extended to address 3D inviscid gust responses. The results of numerical simulations performed using ANSYS Fluent software are compared against analytical solutions. Additionally, the turbulence-airfoil aerodynamic and aeroacoustic response is analyzed. Next, noise signature of a wing with an embedded Cross-Flow Fan (CFF) in turbulent air is investigated. Comparative large-scale 2D simulations are performed for 4 cases including a baseline NACA 65(3)-221 airfoil with the Fowler flap, and the same airfoils with embedded stationary and rotating CFF, as well as, rotating CFF in turbulent air.

Lastly, the uniform ow momentum source model is implemented in OpenFOAM and simulation process is specified in order to obtain stationary decaying turbulence. Effect of turbulence intensity on wake vortex evolution is studied with the use of the momentum source model.

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