Modelování proudění s uvažováním vlivu smáčivosti povrchů

Abstract

Dissertation is focused on modelling of flow with application of the partially wettable wall boundary condition and physical and numerical methods of adhesive coefficient definition. The introductory section provides an overview of the current state of the problem of partial wetting and aims of the dissertation are named. In the next part of the work the basic definitions of surface tension and surface energy of liquids and solid surfaces are described in more details. The example of liquid droplet in contact with the various solid surfaces shows how much the surface and interphase energy of individual phases influences the partial wetting phenomena. The methodology of surface partially wetting investigation and its effect on liquid flow is divided into approaches in terms of physical experiments, mathematical models of selected problems and their numerical modelling. The basic equations for flow of real liquid are introduced, their knowledge is important for numerical modelling of selected tasks. A brief introduction of multiphase models follows; these models solve two issues in dissertation – a water drop on an inclined plane and cavitation in the Laval nozzle. The next part of dissertation provides a summary of the results of physical experiments and numerical testing of selected tasks and specification of adhesive coefficient. The effect of partial wetting surface on flow is studied in simple pipe geometry of circular cross section. The description of physical experiment is introduced, when the measurement of the friction losses in pipes of different materials determined the level of material wettability. This experiment is also solved numerically and the created user-defined function (UDF) including partial wettability of the walls is applied to numerical calculations. Numerical investigation of drop movement on an inclined wettable and partially wettable wall shows that we can simulate this specific problem with the software FLUENT. UDF function for changing the partial wettability of wall is used in numerical calculations. The example of cavitation in the Laval nozzle demonstrates that the wall partial wetting can be used in applications where the cavitation is observed. This task presents a possibility of further using of the partially wettable wall theory in more complex applications. The conclusions from the dissertation, scientific contribution of the work and outputs for practice are formulated at the end of the work.