Improvements in the numerical modeling of turbulence and fluid-structure interaction for the vortex-induced vibrations of a rigid cylinder.

Author(s)

Guilherme Feitosa Rosetti

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2015-06-18

Examining board members

André Luís Condino Fujarra; José Alfredo Ferrari Júnior; Gilder Nader; Celso Pupo Pesce; Fabio Saltara

• Advisor: André Luís Condino Fujarra

Abstract

This thesis presents the development, implementation and application of turbulence and laminar-turbulent transition models and fuid-structure capabilities to address the vortexshedding and vortex-induced vibrations of a rigid cylinder. These numerical developments have been carried out in the computational fuid dynamics (CFD) code ReFRESCO. In the current work, an investigation of the performance of the turbulence modeling with k- SST in a broad range of Reynolds numbers is carried out identifying its modeling deficiencies for this fow. The implementation and systematic application of the scale adaptive simulations (SAS) and the local correlation transition model (LCTM), both combined with the SST, have improved the agreement with experimental results for the cylinder ow, in a novel contribution of this work. The application of verification and validation technique has allowed the estimation of numerical errors and uncertainties for the diferent models. That is also identified as a contribution of this thesis. The combination of SST modeling with imposed motions is carried out as well as with the SAS and LCTM for moderate Reynolds numbers, diferent vibration frequencies and amplitudes, which is considered novel, as few publications address this issue in extent. Regarding the free-moving cylinder capabilities, the present work brings contributions with the application of SST and SASSST with free-moving cylinder for the study of VIV of two degrees of-freedom, low mass ratio and moderate Reynolds numbers, higher than commonly seen in the literature. Finally, the investigation of the relative importance of turbulence effects on the freemoving cylinder and the imposed-motions case, with respect to the fixed case is carried out. A natural conjecture that has been raised early on this work and proved correct is that, for engineering applications, the choice of turbulence modeling strategy is less decisive when the cylinder is moving with prescribed motion and even less stringent, for free motions as the body response filters most of the higher order turbulence effects. That is a relevant observation as it might allow modeling simplifications and the application of CFD tools to a range of engineering problems. (AU)

• FAPESP's process: 10/10939-4 - Fluid-structure interaction of flexible cylindrical structures: numerical and experimental approaches
• Grantee: Guilherme Feitosa Rosetti
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)