A comparative analysis between Newtonian laminarturbulent transition and viscoelastic drag reducing turbulent flows employing the DNS approach

• Ano de defesa: 2019
• Autor(a) principal: Machado, Pedro Perroni Rezende
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal do Rio de Janeiro; Brasil; Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia; Programa de Pós-Graduação em Engenharia Mecânica; UFRJ
• Palavras-chave em Português: drag reduction; polymer solutions; hibernating turbulence; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA
• Link de acesso: http://hdl.handle.net/11422/13522

Recent studies have shown, using numerical simulation of viscoelastic turbulent flows, the presence of flow regimes called active and hibernating turbulence, which alternate in time and present high and low presence of turbulent structures, respectively. The present work aims to study the main diferences between these states, and to analyze their behaviour. Also, we show that this oscillatory behaviour presents itself very similarly in viscoelastic turbulent flows and Newtonian flows in transition to turbulence. These similarities are shown through various physical quantities profiles as well as through the visualization of turbulent structures in the flow, and indicate the existence of an underlying mechanism common to both cases. In addition this work verifies the wall tension criteria used to identify the occurrence of these active and hibernating states, and propose a local approach capable to identify sub-regimes of activation or hibernation in the flow.