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Numerické simulace ferrotekutin
Habera, Michal ; Hron, Jaroslav (advisor) ; Souček, Ondřej (referee)
The stress tensor of a ferrofluid exposed to an external magnetic field is subject to an additional magnetic terms. For a linearly magnetizable medium, such terms results in an interfacial magnetic force acting on the ferrofluid boundaries. This force changes the characteristics of many free-surface ferrofluid phenomena. The aim of this work is to implement this force into Navier-Stokes equations and propose a numerical method to solve them. The interface of ferrofluid is tracked with the use of level-set method and additional reinitialization step assures conservation of its volume. Incompressible Navier-Stokes equations are formulated for divergence free velocity fields while discrete interfacial forces are treated with continuous surface force model. Velocity-pressure coupling is given by projection method. To predict the magnetic force effect quantitatively, Maxwell's equations for magnetostatics are solved in each time step. Finite element method is utilized for the spatial discretization. At the end of the work, equilibrium droplet shape and dripping phenomenon are qualitatively compared to known experimental results. Powered by TCPDF (www.tcpdf.org)
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Study of stagnant water occurrences and dripping waters in caves: Chemical composition and remarks to corrosion of dripstones
Zeman, Ondřej ; Bruthans, J. ; Filippi, Michal ; Vysoká, H.
Slight stagnant water occurrences (drops) were studied in four caves in the Czech Republic and Slovakia. Major components were analyzed (Na+, K+, Ca2+, Mg2+, SO42-, Cl-, NO3-), pH, conductivity and temperature were measured in the field. Results are shown in table 1. Waters coming from condensation differs by higher amount of sulphate and some other components if compared with dripping waters.
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Environmental tracers (18O, 3H, CFCs, SF6) exploitation for study of mean residence time and flow pattern of dripping water and karst springs (Moravian Karst)
Bruthans, J. ; Zeman, Ondřej ; Jež, M. ; Himmel, J. ; Buzek, F. ; Melková, J. ; Oster, H. ; Geršl, M.
Mean residence time and flow pattern was studied in unsaturated zone of Ochoz Cave in southern part of Moravian Karst by means of 18O in the years 2001 to 2003. The results of study showed relatively long residence time in the unsaturated zone (about 50% komponent with residence time exceeding one year). The proportion components coming from different reservoirs were computed from two components (soil/epikarst; meltwater). The results clearly indicate, that more than 50% of water (nearly 100% in 2003) in dripping waters was derived from soil/epikarst water, which originate from (late) summer precipitations (heavy 18O content)! It means that infiltrating snowmelt water was expelling (by piston flow effect) the summer water from soil and/or epikarst. Water from snowmelt was then lost by evapotranspiration in summer time. If this effect is common in Langer period, it can change composition of d18O in dripping waters and hence also in dripstones precipitating from these waters.
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