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Numerical Analysis of Turbulent Flows in Channels of Complex Geometry

Farbos De Luzan, Charles

Abstract Details

2016, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
The current study proposes to follow a systematic validated approach to applied fluid mechanics problems in order to evaluate the ability of different computational fluid dynamics (CFD) to be a relevant design tool. This systematic approach involves different operations such as grid sensitivity analyses, turbulence models comparison and appropriate wall treatments, in order to define case-specific optimal parameters for industrial applications. A validation effort is performed on each study, with particle image velocimetry (PIV) experimental results as the validating metric. The first part of the dissertation lays down the principles of validation, and presents the details of a grid sensitivity analysis, as well as a turbulence models benchmark. The models are available in commercial solvers, and in most cases the default values of the equations constants are retained. The validation experimental data is taken with a hot wire, and has served as a reference to validate multiple turbulence models for turbulent flows in channels. In a second part, the study of a coaxial piping system will compare a set of different steady Reynolds-Averaged Navier Stokes (RANS) turbulence models, namely the one equation model Spalart-Almaras, and two-equation-models standard k-epsilon, k-epsilon realizable, k-epsilon RNG, standard k-omega, k-omega SST, and transition SST. The geometry of interest involves a transition from an annulus into a larger one, where highly turbulent phenomena occur, such as recirculation and jet impingement. Based on a set of constraints that are defined in the analysis, a chosen model will be tested on new designs in order to evaluate their performance. The third part of this dissertation will address the steady-state flow patterns in a Viscosity-Sensitive Fluidic Diode (VSFD). This device is used in a fluidics application, and its originality lies in the fact that it does not require a control fluid in order to operate. This section will discuss the treatment of viscosity in a steady RANS model, and will provide observations that will support the design of an improved device. The fourth part of the document will address the unsteady-state flow patterns in a Bi-Stable Valve (BSV) activated by fluids of different viscosities. This device involves a bi-stable behavior, referred to as the switch, which actuation depends on the viscosity of the fluid. This section will discuss the dependence of initial conditions in unsteady flow simulations, and will provide observations that will support the design of an improved device. In a fifth and final part, compressible large eddy simulation is employed to numerically investigate the laryngeal flow. Symmetric static models of the human larynx with a divergent glottis are considered, with the presence of False Vocal Folds (FVFs). The FVFs are a main factor affecting the closure of the TVFs. The direct link between the FVFs geometry and the motion of the TVFs, and by extension to the voice production, is of interest for medical applications as well as future research works. The presence of the FVFs also changes the dominant frequencies in the velocity and pressure spectra.
Ephraim Gutmark (Committee Chair)
Shaaban Abdallah (Committee Member)
Mark Turner (Committee Member)
237 p.

Recommended Citations

Citations

  • Farbos De Luzan, C. (2016). Numerical Analysis of Turbulent Flows in Channels of Complex Geometry [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1468511618

    APA Style (7th edition)

  • Farbos De Luzan, Charles. Numerical Analysis of Turbulent Flows in Channels of Complex Geometry. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1468511618.

    MLA Style (8th edition)

  • Farbos De Luzan, Charles. "Numerical Analysis of Turbulent Flows in Channels of Complex Geometry." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1468511618

    Chicago Manual of Style (17th edition)