{"id":{"repo_id":"uic","oai_identifier":"oai:figshare.com:article/32995016"},"canonical_url":"https://search.dev.ndltd.org/etd/uic/oai:figshare.com:article/32995016","repository":{"repo_id":"uic","name":"University of Illinois - Chicago","base_url":"https://api.figshare.com/v2/oai"},"display":{"title":"Instability and Transition to Turbulence in Complex Viscoelastic Flows Overlying Porous Surfaces","abstract":"This dissertation investigates the stability characteristics of viscoelastic flows bounded by porous layers, focusing on the coupled effects of elasticity, inertia, and wall permeability. A modified Darcy-Brinkman-Oldroyd-B model is developed to describe the flow behavior within and adjacent to porous media, incorporating fully coupled interfacial conditions between the free-fluid and porous domains. Using this framework, a comprehensive linear stability analysis is conducted for plane Poiseuille flow of an Oldroyd-B fluid confined between rigid, isotropic porous walls. The system is characterized by four key dimensionless parameters: the Reynolds number (RRRR), Weissenberg number (WWWW), permeability parameter (αα), and solvent viscosity ratio (ββ). The analysis reveals a transition from viscoelastic Tollmien--Schlichting (TS)-type modes at low WWWW to a distinct elastic wall mode (EWM) localized near the fluid-porous interfaces at low RRRR. This EWM instability is observed for the first time in this configuration and represents a new mode of viscoelastic instability driven by the coupling between elasticity effects and interfacial permeability. The critical Reynolds number (RRRR) exhibits a strong dependence on WWWW and ββ , with an additional instability branch emerging at higher WWWW. For highly permeable walls (αα = 50), RRRRcccc displays a non-monotonic variation with ββ, markedly different from the trend observed in impermeable configurations. We extend our analysis to a Couette--Poiseuille-type configuration in which the upper wall moves at a constant velocity while the lower boundary consists of a rigid, isotropic porous layer. This asymmetric setup introduces a complex interaction between shear-driven (Couette) and pressure-driven (Poiseuille) components, as well as between viscous and elastic stresses inherent in the Oldroyd-B rheology. The spectral analysis uncovers the emergence of new elasto-inertial wall modes whose onset and growth depend sensitively on wall motion and permeability. The neutral stability results show that the wall velocity (VVww) can either stabilize or destabilize the flow depending on the combined effects of WWWW, αα, and ββ. Overall, this dissertation provides new insights into the hydrodynamic stability of viscoelastic flows interacting with permeable boundaries. The developed model framework and the discovery of the EWM instability advance our understanding of elasto-inertial interactions and offer a foundation for controlling transition phenomena in complex fluid systems of industrial and biological relevance.","abstract_html":"This dissertation investigates the stability characteristics of viscoelastic flows bounded by porous layers, focusing on the coupled effects of elasticity, inertia, and wall permeability. A modified Darcy-Brinkman-Oldroyd-B model is developed to describe the flow behavior within and adjacent to porous media, incorporating fully coupled interfacial conditions between the free-fluid and porous domains. Using this framework, a comprehensive linear stability analysis is conducted for plane Poiseuille flow of an Oldroyd-B fluid confined between rigid, isotropic porous walls. The system is characterized by four key dimensionless parameters: the Reynolds number (RRRR), Weissenberg number (WWWW), permeability parameter (αα), and solvent viscosity ratio (ββ). The analysis reveals a transition from viscoelastic Tollmien--Schlichting (TS)-type modes at low WWWW to a distinct elastic wall mode (EWM) localized near the fluid-porous interfaces at low RRRR. This EWM instability is observed for the first time in this configuration and represents a new mode of viscoelastic instability driven by the coupling between elasticity effects and interfacial permeability. The critical Reynolds number (RRRR) exhibits a strong dependence on WWWW and ββ , with an additional instability branch emerging at higher WWWW. For highly permeable walls (αα = 50), RRRRcccc displays a non-monotonic variation with ββ, markedly different from the trend observed in impermeable configurations. We extend our analysis to a Couette--Poiseuille-type configuration in which the upper wall moves at a constant velocity while the lower boundary consists of a rigid, isotropic porous layer. This asymmetric setup introduces a complex interaction between shear-driven (Couette) and pressure-driven (Poiseuille) components, as well as between viscous and elastic stresses inherent in the Oldroyd-B rheology. The spectral analysis uncovers the emergence of new elasto-inertial wall modes whose onset and growth depend sensitively on wall motion and permeability. The neutral stability results show that the wall velocity (VVww) can either stabilize or destabilize the flow depending on the combined effects of WWWW, αα, and ββ. Overall, this dissertation provides new insights into the hydrodynamic stability of viscoelastic flows interacting with permeable boundaries. The developed model framework and the discovery of the EWM instability advance our understanding of elasto-inertial interactions and offer a foundation for controlling transition phenomena in complex fluid systems of industrial and biological relevance.","abstract_has_math":false,"creators":["Elmira Taheri (24071346)"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-05-01T00:00:00Z","date_published":"2026-05-01T00:00:00Z","updated_at":"2026-07-27T21:33:47Z","subjects":["Fluid Mechanics"],"languages":[],"rights":["In Copyright","Open Access after 2028-05-01"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.25417/uic.32995016.v1","outbound_label":"DOI","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Elmira Taheri (24071346)"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2026-05-01T00:00:00Z"]},{"key":"dc:relation","label":"Dc Relation","values":["https://figshare.com/articles/thesis/Instability_and_Transition_to_Turbulence_in_Complex_Viscoelastic_Flows_Overlying_Porous_Surfaces/32995016"]},{"key":"dc:type","label":"Dc Type","values":["Text","Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Fluid Mechanics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright","Open Access after 2028-05-01"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["10.25417/uic.32995016.v1"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This dissertation investigates the stability characteristics of viscoelastic flows bounded by porous layers, focusing on the coupled effects of elasticity, inertia, and wall permeability. A modified Darcy-Brinkman-Oldroyd-B model is developed to describe the flow behavior within and adjacent to porous media, incorporating fully coupled interfacial conditions between the free-fluid and porous domains. Using this framework, a comprehensive linear stability analysis is conducted for plane Poiseuille flow of an Oldroyd-B fluid confined between rigid, isotropic porous walls. The system is characterized by four key dimensionless parameters: the Reynolds number (RRRR), Weissenberg number (WWWW), permeability parameter (αα), and solvent viscosity ratio (ββ). The analysis reveals a transition from viscoelastic Tollmien--Schlichting (TS)-type modes at low WWWW to a distinct elastic wall mode (EWM) localized near the fluid-porous interfaces at low RRRR. This EWM instability is observed for the first time in this configuration and represents a new mode of viscoelastic instability driven by the coupling between elasticity effects and interfacial permeability. The critical Reynolds number (RRRR) exhibits a strong dependence on WWWW and ββ , with an additional instability branch emerging at higher WWWW. For highly permeable walls (αα = 50), RRRRcccc displays a non-monotonic variation with ββ, markedly different from the trend observed in impermeable configurations. We extend our analysis to a Couette--Poiseuille-type configuration in which the upper wall moves at a constant velocity while the lower boundary consists of a rigid, isotropic porous layer. This asymmetric setup introduces a complex interaction between shear-driven (Couette) and pressure-driven (Poiseuille) components, as well as between viscous and elastic stresses inherent in the Oldroyd-B rheology. The spectral analysis uncovers the emergence of new elasto-inertial wall modes whose onset and growth depend sensitively on wall motion and permeability. The neutral stability results show that the wall velocity (VVww) can either stabilize or destabilize the flow depending on the combined effects of WWWW, αα, and ββ. Overall, this dissertation provides new insights into the hydrodynamic stability of viscoelastic flows interacting with permeable boundaries. The developed model framework and the discovery of the EWM instability advance our understanding of elasto-inertial interactions and offer a foundation for controlling transition phenomena in complex fluid systems of industrial and biological relevance."]},{"key":"dc:title","label":"Title","values":["Instability and Transition to Turbulence in Complex Viscoelastic Flows Overlying Porous Surfaces"]}]}],"canonical_facts":{"dc:creator":["Elmira Taheri (24071346)"],"dc:date":["2026-05-01T00:00:00Z"],"dc:description":["This dissertation investigates the stability characteristics of viscoelastic flows bounded by porous layers, focusing on the coupled effects of elasticity, inertia, and wall permeability. A modified Darcy-Brinkman-Oldroyd-B model is developed to describe the flow behavior within and adjacent to porous media, incorporating fully coupled interfacial conditions between the free-fluid and porous domains. Using this framework, a comprehensive linear stability analysis is conducted for plane Poiseuille flow of an Oldroyd-B fluid confined between rigid, isotropic porous walls. The system is characterized by four key dimensionless parameters: the Reynolds number (RRRR), Weissenberg number (WWWW), permeability parameter (αα), and solvent viscosity ratio (ββ). The analysis reveals a transition from viscoelastic Tollmien--Schlichting (TS)-type modes at low WWWW to a distinct elastic wall mode (EWM) localized near the fluid-porous interfaces at low RRRR. This EWM instability is observed for the first time in this configuration and represents a new mode of viscoelastic instability driven by the coupling between elasticity effects and interfacial permeability. The critical Reynolds number (RRRR) exhibits a strong dependence on WWWW and ββ , with an additional instability branch emerging at higher WWWW. For highly permeable walls (αα = 50), RRRRcccc displays a non-monotonic variation with ββ, markedly different from the trend observed in impermeable configurations. We extend our analysis to a Couette--Poiseuille-type configuration in which the upper wall moves at a constant velocity while the lower boundary consists of a rigid, isotropic porous layer. This asymmetric setup introduces a complex interaction between shear-driven (Couette) and pressure-driven (Poiseuille) components, as well as between viscous and elastic stresses inherent in the Oldroyd-B rheology. The spectral analysis uncovers the emergence of new elasto-inertial wall modes whose onset and growth depend sensitively on wall motion and permeability. The neutral stability results show that the wall velocity (VVww) can either stabilize or destabilize the flow depending on the combined effects of WWWW, αα, and ββ. Overall, this dissertation provides new insights into the hydrodynamic stability of viscoelastic flows interacting with permeable boundaries. The developed model framework and the discovery of the EWM instability advance our understanding of elasto-inertial interactions and offer a foundation for controlling transition phenomena in complex fluid systems of industrial and biological relevance."],"dc:identifier":["10.25417/uic.32995016.v1"],"dc:relation":["https://figshare.com/articles/thesis/Instability_and_Transition_to_Turbulence_in_Complex_Viscoelastic_Flows_Overlying_Porous_Surfaces/32995016"],"dc:rights":["In Copyright","Open Access after 2028-05-01"],"dc:subject":["Fluid Mechanics"],"dc:title":["Instability and Transition to Turbulence in Complex Viscoelastic Flows Overlying Porous Surfaces"],"dc:type":["Text","Thesis"]},"updated_at":"2026-07-27T21:33:47Z"}