Факультет математики і інформатики
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33 результатів
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Документ Stabilization of the turbulent flows in anisotropic viscoelastic tubes(2010) Kizilova, N.; Hamadiche, M.Abstract Flow around the aircrafts and marine vehicles is turbulized that increases the skin-friction drag and fuel consumption. Here stability of the fully developed turbulent flow of an incompressible fluid in the viscoelastic tube is considered. The eddy viscosity concept is considered to be adequate and the flow velocity, wall displacement and pressures in the fluid and solid wall are timeaveraged quantities. Continuity conditions for the components of the velocity and stress tensor at the fluid-wall interface and no displacement condition at the outer wall of the tube are considered. Solution of the coupled system has been found in the form of the normal mode and the obtained system has been studied using the numerical technique described in [1,2]. The temporal and spatial eigenvalues and the dependencies of the temporal and spatial amplification rates on the rheological parameters of the wall have been computed. It was shown stability of the modes can be increased by a proper choice of the wall parameters. Successful combinations of the wall thickness, elasticity and viscosity have been found for a large variety of materials. It was shown a substantial reduction in the viscous wall shear stress accompanied by a decrease in the turbulence production or Reynolds stress can be reached via using the viscoelastic coating on the rigid surface. The obtained results are in a good agreement with recent direct numerical computations [3].Документ Bio-Thermo-Hydro-Mechanics: problems and perspectives(2011) Kizilova, N.; Samit, R.; Petrov, N.; Szekeres, A.Документ Nature Inspired Optimal Composites(2010) Kizilova, N.; Szekeres, A.Документ Документ Microimplants, head gears and bracket systems in orthodontic tooth movement: a biomechanical study(2010) Kizilova, N.; Geramy, A.Документ A mixture model of differentially growing biological continua(2010) Kizilova, N.; Stein, A.Документ A 1000-tube model of human systemic arterial vasculature(2010) Kizilova, N.Документ Stability and control of the blood flow in the arterial vessels as multilayered anisotropic tubes(2010) Kizilova, N.; Hamadiche, M.Документ Optimal long-distance transport systems in nature: control and applications(2007) Kizilova, N.Long-distance conducting systems in high plants and animals are presented by networks of rigid tubes with porous walls (in plants) or distensible tubes with impermeable walls (in animals). Geometrical relationships between the diameters, lengths and branching angles of separate conducting vessels have been studied and the results of the comparative analysis are presented. It was shown that the principles of construction of the transport systems are similar in animals and plants and correspond to the optimal pipelines with impermeable and permeable walls accordingly. The optimization criterion is the total energy expenses W for the fluid delivery and construction of the system. Global optimality at the systemic level is provided by local optimality conditions in each conducting element. It is shown that complexity of the branching system of the optimal tubes leads to certain regularities in the hydraulic and wave properties of the systems. The obtained regularities and the principles of design of the long-distance transportation networks in Nature can be used in biomedical applications and technique.Документ Novel methods of pulse wave diagnostics based on compression of a superficial artery(2007) Kizilova, N.Pulse wave propagation and reflection in the branching systems of viscoelastic tubes and complex resistances as a model of arterial vasculature is considered. Axisymmetric wave motion of a viscous incompressible liquid in the system is investigated in application to the pressure and flow wave propagation in the system. Expression for the input admittance of the system taking into account wave reflection at the end of the tube is obtained. The dependence of the input admittance on the geometrical and mechanical parameters of the system is investigated. It is shown that the parameters of the pressure wave (the modules and phases of different harmonics) at the inlet of the system give information on the state (normal or pathological) of the inner organs. It is shown that after a proper compression (slight or deep) some harmonics can be amplified while the others are attenuated. Based on the theory of resonant harmonics of different inner organs the novel method of pulse wave palpation is proposed. The results are compared to some other methods as separation of the pressure wave into the forward and backward components, estimation of the parameters of the reflected wave and wave-intensity analysis.