|
|
Qualitative properties of solutions to equations of fluid mechanics
Tichý, Jakub
Qualitative properties of solutions to equations of fluid mechanics Mgr. Jakub Tichý Supervisor: doc. Mgr. Petr Kaplický, Ph.D. Department: Department of Mathematical Analysis Abstract This thesis is devoted to the boundary regularity of weak solutions to the system of nonlinear partial differential equations describing incompressible flows of a certain class of generalized Newtonian fluids in bounded domains. Equations of motion and continuity equation are complemented with perfect slip boundary conditions. For stationary generalized Stokes system in Rn with growth condi- tion described by N-function Φ the existence of the second derivatives of velocity and their regularity up to the boundary are shown. For the same system of equa- tions integrability of velocity gradients is proven. Lq estimates are obtained also for classical evolutionary Stokes system via interpolation-extrapolation scales. Hölder continuity of velocity gradients and pressure is shown for evolutionary generalized Navier-Stokes equations in R2 . Keywords Generalized Stokes and Navier - Stokes equations, incompressible fluids, perfect slip boundary conditions, regularity up to the boundary
|
|
|
On the role of boundary conditions in the time periodic flow of incompressible fluid in tube
Hrůza, Jan ; Bulíček, Miroslav (advisor) ; Málek, Josef (referee)
The goal of this work is to find a solution to the problem of incompressible fluid flow in the pipe induced by a time periodic pressure gradient. Boundary conditions including a time derivative of velocity field are considered. This type of boundary conditions models a dynamic response of the fluid at the boundary and such behaviour can be used for example in molten polymers fluid modeling. First we look for a specific form of the solution using the Fourier method. The solution is decomposed into a linear combination of functions based on the Bessel function of zero order. We then study these functions in more details. Then we investigate the convergence of sequence of approximative solutions in the space of continuous functions and in the Lebesgue space. In proofs we use the properties of the Bessel function and in particular we investigate the distribution of the roots of Bessel function. We also use a numerical software to compute an approximative solution based on the Fourier method. 1
|
|
|
Inflow and outflow boundary conditions on artificial boundaries
Kubáč, Vojtěch ; Lanzendörfer, Martin (advisor) ; Tůma, Karel (referee)
In the beginning of this thesis we introduce the basic properties of the fluid mechanics, mainly for stationary incompressible flow. In the next section we show the weak formulation of derived (Navier-Stokes) equations and some of the boun- dary conditions. Finally, the biggest part of this thesis is occupied by numerical experiments with simple planar flows. We seek for suitable inflow and outflow boundary conditions on an artificial boundary for the problem of outflow from a long channel or inflow to that channel. 1
|
|
|
Qualitative properties of solutions to equations of fluid mechanics
Tichý, Jakub
Qualitative properties of solutions to equations of fluid mechanics Mgr. Jakub Tichý Supervisor: doc. Mgr. Petr Kaplický, Ph.D. Department: Department of Mathematical Analysis Abstract This thesis is devoted to the boundary regularity of weak solutions to the system of nonlinear partial differential equations describing incompressible flows of a certain class of generalized Newtonian fluids in bounded domains. Equations of motion and continuity equation are complemented with perfect slip boundary conditions. For stationary generalized Stokes system in Rn with growth condi- tion described by N-function Φ the existence of the second derivatives of velocity and their regularity up to the boundary are shown. For the same system of equa- tions integrability of velocity gradients is proven. Lq estimates are obtained also for classical evolutionary Stokes system via interpolation-extrapolation scales. Hölder continuity of velocity gradients and pressure is shown for evolutionary generalized Navier-Stokes equations in R2 . Keywords Generalized Stokes and Navier - Stokes equations, incompressible fluids, perfect slip boundary conditions, regularity up to the boundary
|
|
|
Qualitative properties of solutions to equations of fluid mechanics
Tichý, Jakub ; Kaplický, Petr (advisor) ; Bulíček, Miroslav (referee) ; Diening, Lars (referee)
Qualitative properties of solutions to equations of fluid mechanics Mgr. Jakub Tichý Supervisor: doc. Mgr. Petr Kaplický, Ph.D. Department: Department of Mathematical Analysis Abstract This thesis is devoted to the boundary regularity of weak solutions to the system of nonlinear partial differential equations describing incompressible flows of a certain class of generalized Newtonian fluids in bounded domains. Equations of motion and continuity equation are complemented with perfect slip boundary conditions. For stationary generalized Stokes system in Rn with growth condi- tion described by N-function Φ the existence of the second derivatives of velocity and their regularity up to the boundary are shown. For the same system of equa- tions integrability of velocity gradients is proven. Lq estimates are obtained also for classical evolutionary Stokes system via interpolation-extrapolation scales. Hölder continuity of velocity gradients and pressure is shown for evolutionary generalized Navier-Stokes equations in R2 . Keywords Generalized Stokes and Navier - Stokes equations, incompressible fluids, perfect slip boundary conditions, regularity up to the boundary
|
|
|
Flows of incompressible fluids with pressure-dependent viscosity (and their application to modelling the flow in journal bearing)
Lanzendörfer, Martin ; Málek, Josef (advisor) ; Knobloch, Petr (referee) ; Süli, Endré (referee)
Title: Flows of incompressible fluids with pressure-dependent viscosity (and their application to modelling the flow in journal bearing) Author: Martin Lanzendörfer Department: Mathematical Institute of Charles University Supervisor: prof. RNDr. Josef Málek, DSc. Abstract: The viscosity of the fluids involved in hydrodynamic lubrication typically depends on pressure and shear rate. The thesis is concerned with steady isothermal flows of such fluds. Generalizing the recent results achieved in the case of homogeneous Dirichlet boundary conditions, the existence and uniqueness of weak solutions subject to the boundary conditions employed in practical applications will be established. The second part is concerned with numerical simulations of the lubrication flow. The experiments indicate that the presented finite element method is successful as long as certain restrictions on the constitutive model are met. Both the restrictions involved in the theoretical results and those indicated by the numerical experiments allow to accurately model real-world lubricants in certain ranges of pressures and shear rates. The last part quantifies those ranges for three representative lubricants. Keywords: existence and uniqueness of weak solutions, finite element method, pressure- thickening, shear-thinning, incompressible fluids,...
|
guest ::
