We study the dynamic response of a metal slab containing electron gas described by the hydrodynamic model with dispersion. The resulting wave equation for the perturbed electron density is solved by means of the Green’s function that satisfies Neumann boundary conditions at the endpoints of the slab. This solution is coupled with the electrostatic potential, which is expressed in terms of the Green’s function for the Poisson equation for a layered structure consisting of three dielectric regions. As an illustration, a set of dispersion relations for eigenfrequencies is deduced for the plasma oscillations in the electron gas, corresponding to both the surface and the bulk modes of even and odd symmetry with respect to the center of the metal slab.
A two-dimentional hydrodynamic model of a rheokinetic fluid during filling a thin and long mold packed with reinforcement materials are proposed. A core layer of the mold is a porous and rather thick spacer mat. The location of other denser and thinner reinforcement materials into the mold was symmetrical with respect to the spacer mat. During mold filling the fluid easily flows along the core spacer mat and simultaneously impregnates the peripheral reinforcement mats. The model allows to simulate the flow front propagation of the fluid and pressure rise inside the mold during filling. In order to verify the model an original glass mold has been designed and built. The experimental results for the flow front propagation of the fluid were compared with the model predictions and a good coincidence between them has been obtained. For correct comparison of the experimental pressure profiles with the calculated data, the pressure losses in the mold gate must be taken into consideration. These losses can essentially exceed the pressure level into the mold.
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Thermodynamic flow model as a necessary tool in hydraulic analysis of generał fluming and precipitation sewage treatrnent systems wor-king. Review ofcornputer hydrodynamic models. Example simulation of sewage system working in SewerPac pack.
Przedstawiono model ruchu transkrytycznego umożliwiający opis przepływu wody w małych rzekach górskich. Model bazuje na specjalnych rozwiązaniach przybliżonych, opartych na aproksymacji Roe'go zagadnienia Riemanna i zastosowaniu niejawnego schematu dyskredytacji po czasie. Model został skalrbrowany dla odcinka Ścinawki.
EN
The article presents transcritical motion model enabling a description of water flow in small mountain rivers. The model is realised on the basis of special approximate solutions, based on Roe's approximate Riemann solver and the use of the non-evident scheme of discontinuity after a definite time. The model was calibrated for a section of the Ścinawka.
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Wastewater flow control in sewerage systems is crucial for their effective operation but it is equally important from the point of view of wastewater treatment efficiency and surface waters quality. The paper presents the foundations of mathematical modelling and development of simulation tools for the solutions of a retention reservoir. On the grounds of a case study, possibilities are presented to use the developed program for the dimensioning of reservoirs of a defined type based on theoretical wastewater flow functions and hydrographs obtained on the grounds of the catchment hydrodynamic model.
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