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Stability of stationary flows of non-Newtonian heat conducting fluid in 2D
Wintrová, Lucie ; Kaplický, Petr (advisor) ; Pokorný, Milan (referee)
This thesis aims to study the Navier-Stokes-Fourier problem with the entropy equa- tion. In particular, we want to define the notion of a solution and prove its existence. We approach this problem by modifying techniques used in several papers studying the generalized NSF system and the entropy equality and we want to conclude similar results. We are treating the two-dimensional case as opposed to the more frequent 3D case, hence we were able to relax conditions on the initial data. Firstly, we formulate the definition of a weak solution and impose sufficient conditions to prove its existence. In particular, we will require a bound p ≥ 2 for the power-law index of the Cauchy stress tensor. Next, we show that there exists a solution to Navier- Stokes-Fourier system (u, ϑ) fulfilling our definition. Lastly, we show that this solution additionally fulfills the entropy equality for η = log ϑ. 1
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Differential equations with eigenvalue in boundary conditions
Váša, Ondřej ; Kaplický, Petr (advisor) ; Pokorný, Milan (referee)
The goal of this thesis was to study Stokes problem with eigenvalue in bound- ary condition. We were in particular interested in determining the asymptotic be- haviour of the sequence of eigenvalues. We approached this problem by modifying techniques used in several papers studying asymptotic behaviour of eigenvalues in boundary condition for Steklov problem and we wanted to conclude similar re- sults. Firstly, we introduced some theoretical results yielding that the eigenvalue sequence of the problem is corresponding to an eigenvalue sequence of a certain compact and self-adjoint operator. Next, we explicitly calculated precise asymp- totic behaviour of eigenvalues of auxiliary problems on simple domains, however, due to technical difficulties, we were only able to do in two and three dimensions. Finally, by using Min-max Theorem, we managed to get estimates of eigenvalues of the original problem on any bounded C2 domain by eigenvalues of considered auxiliary problems and thus by applying previous results, we managed to prove the desired asymptotic behaviour. 1
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Using Version Control Systems to Support Learning
Pokorný, Milan ; Jeřábek, Tomáš (advisor) ; Štípek, Jiří (referee)
The thesis examines version control systems (VCs) and the possibilities of their use in information technology classes. At first, various solutions for version management are evaluated. As a result, a decentralized system called Git is deemed the most appropriate to be used in education. The text further explains the details of how Git works while also introducing some of the relevant training software and Git extensions. The thesis continues by exploring the role of version control systems in education, their teaching, and use as a didactic tool. The final chapters are practically oriented and include the description of processes which allow source code version control to be used within a student group environment. The thesis concludes with an overall evaluation of the use of version management systems in teaching, including practical recommendations and examples.
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Matematická analýza regularizovaného modelu viskoelastické nenewtonovské tekutiny
Šalom, Pavel ; Pokorný, Milan (advisor) ; Bulíček, Miroslav (referee)
In this thesis we provide an existence result for a regularized model of viscoelastic non- newtonian fluid. We consider incompressible fluid with shear rate dependent viscosity and with Cauchy stress tensor capable to describe stress relaxation. An elastic part of the Cauchy stress tensor is governed by Oldroyd-type differential equation. In particular, we are interested in fluids with strong shear thinning effect. We prove that if the viscosity function µ (D) is such that tensor µ (D) D is p-coercive, monotone and has (p − 1)-growth for p > 6 5 and some other additional assumptions are satisfied, then there exists a solution to the system of PDEs describing the flow in a bounded domain. The proof is not simple because the convective term is not integrable with a high power. The problem is solved using Lipschitz truncation method for evolution PDEs. 1
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Regularity criteria for instationary incompressible Navier-Stokes equations
Axmann, Šimon ; Pokorný, Milan (advisor) ; Neustupa, Jiří (referee)
Title: Regularity criteria for instationary incompressible Navier-Stokes equations Author: Šimon Axmann Institute: Mathematical Institute of Charles University Supervisor: doc. Mgr. Milan Pokorný, Ph.D., Mathematical Institute of Charles University Abstract: In the present thesis we study the global conditional regularity of weak solutions to the Cauchy problem for instationary incompressible Navier-Stokes equations in three space dimensions. In the first section, we present an overview of known conditions implying the full regularity of the equations under conside- ration. For the sake of clarity, we expose only the regularity criteria on the scale of Lebesgue spaces, especially in terms of the velocity and its components, the gradient of the velocity and its components, the pressure and the vorticity. In the subsequent sections, we generalize four regularity criteria using two different techniques. We are able to replace one velocity component or its gradient, consi- dered in the known results, by a projection of the velocity into a general vector field. For the purpose of the second method, we also generalize the multiplicative Gagliardo-Nirenberg inequality.
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Fourier method for solving partial differential equations
Tůma, Karel ; Pokorný, Milan (advisor) ; Knobloch, Petr (referee)
Na./cv prace: Fouricrova metoda pro feseni parc.ialnich dirornncialnich rovnic Autor: Karri Tuma Katedra (ust.av): Matematicky ust.av UK Vedouci bakalafske praoo: Mgr. Milan Pokorny, Ph.D. e-mail vodouciho: pokorny@karlin.mff.cuni.cz Abstra.kt: V pfedlo/ene praci odvodime rovnici vedeni tepla a.rovnici slruny. Ty pak nasledno. fesime v jodno prost.orove dimenxi ponioci Fonricrovy me- tody apocivajfci v separaci promennych a nale/eni feseni vc l.varn ncko- nccnc' fady. Zaljyvainc so t.fonii ru/nymi okrajovynii podininkanii. Dah^ vy- sotrujomo vlastnosii foscni tcchlo dvou problcmu. Provadinio analyzu kon- vorgtuicc fx'soni vu tvaru fad v -/avislosti na pocat.ocnich podminkach uloh. Uka/c-me. /o pornoci Fouriorovy inolody l/.c fosil lako stucionarni ulohy, konkrctno so zabyvanio Laplaccoviju rovnici s okrajovynii podminkami na ruznych oblasloch (kruh. vyscc. vyscc mc/ikru/f, mraikru/i). Klicova slova: Parcialni diforoncialni rovnico, Fouricrova tnot.oda, rovnico vodoni lopla, rovnico sLruny. Title: Fourier method for solving partial differential equations Author: Karel Tuma, Department: Matematicky ustav UK Supervisor: Mgr. Milan Pokorny. Ph.D. Supervisor's e-mail address: pokorny@karlin.raff.cuni.cz Abstract: In the present work we derive the heat equation and the wave equation. They arc- solved in one space...
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