Modelling of low Reynolds numbers turbulent flow in the aortic valve

In the dissertation, patient-specific aortic valve flows are investigated by using numerical methods. The main object of research is aortic valve flow with low Reynolds numbers turbulence and its numerical models. The main goal of the dissertation is to develop and investigate a numerical model for aortic valve flows with low Reynolds numbers turbulence.

The dissertation consists of introduction, 3 chapters, general conclusions, references, a list of publications by the author on the topic of the dissertation, a summary in English and 3 annexes.

The introduction reveals the research problem, relevance of the work, describes the objective of research, formulates the aim and tasks of the work, and describes the research methodology, scientific novelty of the work, the practical significance of the results, defended statements. The introduction ends in presenting the author’s publications on the topic of the dissertation, listing the made presentations in conferences and defining the structure of the dissertation.

Chapter 1 revises the literature. Numerical methods for aortic valve flows are overviewed. The attention is focused on turbulence models applied to aortic valve flows and outlet boundary conditions used in the case of backflows.

Chapter 2 presents the methodology of work: the applied geometric models of the aortic valve, the differential equations, boundary conditions and numerical schemes of the finite volume method. The differential Navier-Stokes equations are supplemented by the shear-stress transport k-ω turbulence model with intermittency transition equation. The outlet boundary conditions are proposed to to solve the backflow issues. The employed finite volume method and numerical schemes are described as well as the used unstructured meshes of various deensity and the discretization of the boundary layer.

Chapter 3 discusses the numerical results. The computating infrastructure and computational efficiency are described. Selection of the main numerical parameters, finite volume meshes and the size of time step is discussed. Results of various types of outlet boundary conditions are investigated to evaluate their influence on the resulting backflows. A comparative study of the numerical results obtained by using various turbulence models is also performed. The general conclusions of the chapter are presented.

8 scientific articles were published on the topic of the dissertation: 5 in Clarivate Analytics Web of Science Journals that have a citation index, 1 in Conference Proceedings, 2 in other international database publications. Results of the dissertation were presented in 5 international conferences held in Lithuania and abroad.

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DOI: https://doi.org/10.20334/2021-003-M