The present paper investigates the thermal convection in Walters‘ (model B‘) fluid saturated by a porous medium in the presence of uniform vertical magnetic field. For the porous medium, Brinkman model is employed and Walters‘ (model B‘) fluid model is used to describe the rheological behavior of elastico-viscous fluid. By applying normal mode analysis method, the dispersion relation has been derived and solved analytically. It is observed that the magnetic field and viscoelasticity introduce oscillatory modes. For stationary convection, it is observed that the Walters‘ (model B‘) elastico-viscous fluid behaves like an ordinary Newtonian fluid. The effects of Darcy number, magnetic field and medium permeability have been discussed analytically and numerically in detail. The case of overstability has also been discussed and a sufficient condition for the non-existence of overstability is derived. and Obsahuje seznam literatury, názvosloví a řeckých znaků
This article deals with the numerical simulation of intensity distribution of the magnetic field by means of the final elements method (FEM). The computational model describes the distribution normal and tangential components of magnetic field intensity at the front and the close vicinity of the front of the external probe of the method of the magnetic spot. The maximum value of the normal component of remanent intensity is 330 kAm-1 when the probe is placed at a distance of 2 mm from the surface. The maximum value of the tangential component of remanent intensity is 230 kAm-1 when the probe is placed at a distance of 2 mm from the material surface. The intensity values were achieved with a maximum current amplitude of 6.91 A. The calculation was determined of the shape and topography of magnetic spot, which will enable the optimisation of measurement. and Článek se zabývá numerickou simulací rozložení intensity magnetického pole pomocí metody konečných prvků. Výpočtový model popisuje rozložení normálové a tangenciální složky intensity magnetického pole metody magnetické skvrny pod čelem příložné sondy. Maximální hodnota normálové složky remanentní intensity je 330 kAm-1 ve vzdálenosti sondy 2 mm nad povrchem materiálu. Maximální hodnota tangenciální složky remanentní intensity je 230 kAm-1 ve vzdálenosti 2 mm nad povrchem materiálu. Hodnoty intensity byly simulovány pro maximální amplitudu proudu 6,91 A. Výpočet směřoval ke zjištění tvaru a topografie magnetické skvrny, které budou sloužit k optimalizaci měření.
The article presents the mathematical model non-homogenous, isotropic environment, where is possible to create various types of flows (the chemical reaction flow, the diffusion flow, the heat flow, the electromagnetic flow). and Obsahuje seznam literatury
The paper is focused into the research of distribution (2D) of magnetic field for analysis of samples with magnetic active films during the measurement of dark mode spectroscopy (DMS). In shortness is here described construction of the electromagnet and modelling of its magnetic field. and Příspěvek je zaměřen na studium rozložení (2D) magnetického pole pro analýzu vzorků s magneticky aktivními vrstvami při měření metodou tmavé vidové spektroskopie (DMS). Stručně je zde popsána konstrukce realizovaného elektromagnetu a jeho modelování.