Paper deals with subject of identification of aerostatic journal bearings dynamic properties with use of Rotor Kit Bently Nevada superstructure. Different bearing types were experimentally investigated and their static and dynamic characteristics were identified. Various methods of identification were used and spectral and modal properties of the system were calculated. Computer program was revised on the basis of experimental data. The influence of non-diagonal stiffness and damping elements was investigated by numeric stimulation. and Obsahuje seznam literatury
Investigations indicate that correct estimation of seasonal thermal stratification in a dam reservoir is very important for the dam reservoir water quality modeling and water management problems. The main aim of this study is to develop a hydrodynamics model of an actual dam reservoir in three dimensions for simulating a real dam reservoir flows for different seasons. The model is developed using nonlinear and unsteady continuity, momentum, energy and k-ε turbulence model equations. In order to include the Coriolis force effect on the flow in a dam reservoir, Coriolis force parameter is also added the model equations. Those equations are constructed using actual dimensions, shape, boundary and initial conditions of the dam and reservoir. Temperature profiles and flow visualizations are used to evaluate flow conditions in the reservoir. Reservoir flow’s process and parameters are determined all over the reservoir. The mathematical model developed is capable of simulating the flow and thermal characteristics of the reservoir system for seasonal heat exchanges. Model simulations results obtained are compared with field measurements obtained from gauging stations for flows in different seasons. The results show a good agreement with the field measurements.
The paper concerns a contemporary problem emerging in philosophy of science about the explanatory status of mathematical models as abstractions. The starting point lies in the analysis of Morrison’s discrimination of models as idealizations and models as abstractions. There abstraction has a special status because its non-realistic nature (e.g. an infinite number of particles, an infinite structure of fractal etc.) is the very reason for its explanatory success and usefulness. The paper presents two new examples of mathematical models as abstractions – the fractal invariant of phase space transformations in the dynamic systems theory and infinite sets in the formal grammar and automata theory. The author is convinced about the indispensability of mathematical models as abstraction, but somehow disagrees with the interpretation of its explanatory power. and Článek se zabývá současným problémem ve filosofii vědy o vysvětlujícím stavu matematických modelů jako abstrakcí. Výchozím bodem je analýza Morrisonovy diskriminace modelů jako idealizací a modelů jako abstrakcí. Abstrakce má zvláštní stav, protože jeho nerealistická povaha (např. Nekonečný počet částic, nekonečná struktura fraktálu apod.) Je právě důvodem vysvětlujícího úspěchu a užitečnosti. Článek představuje dva nové příklady matematických modelů jako abstrakce - fraktální invariant transformací fázových prostorů v teorii dynamických systémů a nekonečné množiny ve formální teorii gramatiky a automatů. Autor je přesvědčen o nezbytnosti matematických modelů jako o abstrakci,
A numerical model of the unsaturated water movement in capillary pores of soil matrix was used for the water flow in macropores and in capillary pores. Hydraulic conductivity dependance on soil moisture content for macropores was linearized between two soil moisture contents: the saturated soil matrix moisture content and the saturated soil moisture content with macropores. The second one is neither possible to define unambiguously nor measure. It is possible to determine its optimal value from the measured moisture content courses and by those, calculated by mathematic model. and Na výpočet pohybu vody v dvoch oblastiach, v makropóroch a kapilárnych póroch bol použitý numerický model pohybu vody v kapilárnych póroch vodou nenasýtenej pôdnej matrice. Závislosť hydraulickej vodivosti od vlhkosti pôdy pre makropórovú oblasť bola linearizovaná medzi dvoma vlhkosťami pôdy: vlhkosťou vodou nasýtenej pôdnej matrice a vlhkosťou vodou nasýtenej pôdy aj s makropórmi. Poslednú z týchto dvoch nemožno jednoznačne definovať ani namerať. Z priebehov vlhkostí vo vybraných hĺbkach pôdy určených meraním a matematickým modelovaním môžeme určiť optimálnu hodnotu vlhkosti vodou nasýtenej pôdy aj s makropórmi.
A detailed analysis of dynamical properties of five-blade-bundle mathematical model was carried out with the aim to investigate how the damping elements made of rubber inserted into slots between blades heads influence the response curves at different distribution of exciting harmonic forces. Viscous-elastic linear Voigt-Kelvin model was used for modeling the rheological properties of damping elements. Constant values of stiffness and damping parameters were supposed at analysis. The orthogonality of excitation forces distribution to the other eigenmodes of blades bundle is applied at insulated selected resonance. and Obsahuje seznam literatury
This study seeks to derive an original multicriterial decision making model for operative control of water quality in the water reservoir. The model design is based on the theory of dynamic systems control. It incorporates simulation modelling methods with the hydrodynamic reservoir and multicriterial optimization methods. The research aims to derive an algorithm for operating rules of the reservoir under any operating conditions and for the given criteria of control. The study presents the outcomes of the application of model quality control of water withdrawal from the Římov reservoir on the Malše River. and Studie odvozuje původní vícekriteriální rozhodovací model pro operativní řízení kvality odebírané vody z vodárenské nádrže. Model vychází z teorie řízení dynamických systémů a propojuje se v něm metodologie simulačního modelování s hydrodynamikou nádrží a metodami vícekriteriální optimalizace. Cílem řešení je odvodit algoritmus pro regulační zásahy (manipulace) na nádrži při libovolných provozních podmínkách a pro stanovená kritéria řízení. Studie uvádí výsledky aplikace modelového řízení kvality vody v nádrži Římov na Malši.
This study seeks to derive an original multicriterial decision making model for operative control of water quality in the water reservoir. The model design is based on the theory of dynamic systems control. It incorporates simulation modelling methods with the hydrodynamic reservoir and multicriterial optimization methods. The research aims to derive an algorithm for operating rules of the reservoir under any operating conditions and for the given criteria of control. The study presents the outcomes of the application of model quality control of water withdrawal from the Rimov reservoir on the Malše River.