Numerical simulation of non-Newtonian fluids flow over surfaces

التفاصيل البيبلوغرافية
العنوان:	Numerical simulation of non-Newtonian fluids flow over surfaces
بيانات النشر:	KTH, Teknisk mekanik Stockholm : KTH Royal Institute of Technology 2023
تفاصيل مُضافة:	Bazesefidpar, Kazem
نوع الوثيقة:	Electronic Resource
مستخلص:	Wetting of surfaces by droplets of non-Newtonian fluids is important for various industrial and natural processes such as coating and cleaning of surfaces and inkjet printing, to name a few. Viscoelastic fluids are compounds of a very small amount of polymers and solvent. They are categorized as non-Newtonian fluids, and they exhibit both elasticity and shear dependent viscosity. Despite their relevance and abundance in our environment, dynamic wetting of viscoelastic fluids has been studied much less than that of the Newtonian fluids. Furthermore, many of the viscoelastic studies make simplifying assumptions of the contact line movement, for example, a constant value of the contact angle independent of the spreading speed of the droplet. In this thesis work, we implement a numerical framework for dynamic contact line problems of viscoelastic fluids, taking into account contact line friction or contact line hysteresis when necessary. We solve the coupled Cahn-Hilliard, Navier-Stokes and viscoelastic constitutive models to reveal detailed information about the flow physics, such as the polymeric stress distributions inside the drops. Especially interesting is the vicinity of discontinuity regions e.g. the contact-line and liquid bridge between the coalescing drops. First, we present the idea of dual-resolution grids to address the high interfacial resolution requirements for a viscoelastic two-phase flow. In particular, a dual-resolution algorithm is presented and validated for the wetting of viscoelastic fluids. Secondly, we apply our algorithm to investigate the effect of non-Newtonian properties on jumping of two merging droplets from a superhydrophobic surface, a problem which might be of interest for self-cleaning surfaces. In the last part, the physical effects of non-Newtonian properties are investigated on both the initial wetting regime on a smooth hydrophilic surface and the pinning and depinning of a droplet in the presence of the contact angle hysteresis. Vätning av icke-newtonska vätskor på en yta är ett viktigt och vanligt förekommande problem i naturliga och industriella processer såsom ytrengöring, olika ytbeläggningar, bläckstråleskrivare för att nämna några exempel. Viskoelastiska vätskor består av polymerer och lösningsmedel och hör till kategorin icke-Newtonska vätskor, och de uppvisar båda elasticitet och skjuvningsberoende viskositet. Trots icke-Newtonska vätskors relevans i vardagen har deras vätningsegenskaper studerats mycket mindre hittils än processen för Newtonska vätskor. Vidare så används ofta förenklade antaganden av kontaktlinjens rörelse, såsom ett konstant värde av kontaktvinkeln som inte beror på spridningshastigheten. I detta arbete implementerar vi en numerisk lösningsmetod för dynamiska vätningsproblem av viskoelastiska droppar. Vi löser de kopplade Cahn-Hilliard, Navier-Stokes och viskoelastiska konstitutiva ekvationerna tillsammans för att få fram detaljerad information av strömningen såsom fördelningen av viskoelastiska spänningar inuti droppen. Speciellt intressant är att fokusera på områden där egenskaperna varierar diskontinuerligt, till exempel kontaktlinjer och i vätskebryggan mellan koalescerande droppar. Först presenterar vi tanken bakom duala nät för att öka upplösningen nära ytan i viskoelastiska tvåfasflöden. I synnerhet presenterar vi ekvationerna och valideringen av den numeriska lösaren för vätning av viskoelastiska vätskor. I den andra delen undersöker vi effekten av de icke-newtonska egenskaperna påverkar två koalescerande droppar som hoppar från en superhydrofob yta, ett problem av potentiellt intresse för självrengörande ytor. I den sista delen undersöks de viskoelastiska effekternas betydelse för snabba vätningsprocesser på en slät hydrofil yta samt för rörelsen av droppar med kontaktlinjehysteres. QC 230824
مصطلحات الفهرس:	dynamic wetting, viscoelasticity, non-Newtonian fluids, contact- angle hysteresis, droplet spreading, self-propelled jumping, dynamisk vätning, viskoelasticitet, icke-Newtonska vätskor, kontaktlinjehysteres, dropparnas spridning på ytor, spontan hoppning av droppar från ytor, Fluid Mechanics and Acoustics, Strömningsmekanik och akustik, Doctoral thesis, comprehensive summary, info:eu-repo/semantics/doctoralThesis, text
URL:	http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-334511 TRITA-SCI-FOU ; 2023:43
الإتاحة:	Open access content. Open access content info:eu-repo/semantics/openAccess
ملاحظة:	application/pdf English
أرقام أخرى:	UPE oai:DiVA.org:kth-334511 0000-0001-6819-214X urn:isbn:978-91-8040-682-6 1400012021
المصدر المساهم:	UPPSALA UNIV LIBR From OAIster®, provided by the OCLC Cooperative.
رقم الأكسشن:	edsoai.on1400012021
قاعدة البيانات:	OAIster

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