This paper deals with the numerical simulation of spherical particle saltation in a channel with a rough transversely tilted bed. The numerical model presented is based on the 3D model of spherical particle saltation developed by the authors, which takes into account the translational and rotational particle motion. The stochastic method and the concept of a contact zone were used for the calculation of a particle trajectory and its dependence on the bed lateral slope, particle diameter, and shear velocity. The effect of the bed lateral slope results in a deviation of the particle trajectory from the downstream direction. Some examples of the calculation are presented. The trajectories of the saltating particles starting their movements from one point were calculated and it was shown that they are of random character and together create a bundle or fascicle of trajectories. It was found that the centrelines of the bundles can be approximated by the straight lines for low and moderate values of the bed transverse slope, i.e. slopes less than 20°. The angle of deviation of the centreline from the downstream direction increases when the bed lateral slope and/or the particle diameters increase. However, with increasing shear velocity, the deviation angle decreases. Due to the lateral bed slope the particles are sorted according to their size, and the criteria for sorting particles were defined. An example of the particle sorting was calculated and the separable and nonseparable regions were determined. and Studie popisuje numerickou simulaci saltačního pohybu kulovité částice v korytě s příčně skloněným drsným dnem. Předložený numerický model je založen na autory vyvinutém 3D modelu saltačního pohybu kulovité částice, který počítá s translačním i rotačním pohybem částice. Pro výpočet trajektorie částice a její závislosti na příčném sklonu dna koryta, průměru částice a smykové rychlosti nosné kapaliny byla použita stochastická metoda a koncept kontaktní zóny. Vlivem příčného sklonu dna koryta dochází k odchylce trajektorie částice od směru proudu. Trajektorie částic začínajících svůj pohyb v jednom bodě byly vypočteny a bylo ukázáno, že trajektorie jsou náhodného charakteru a tvoří společně svazek trajektorií, jehož osa může být pro nízké a střední hodnoty příčného sklonu dna koryta aproximována přímkou. Vlivem příčného sklonu dna koryta může dojít k roztřídění částic podle velikosti. Bylo spočteno několik příkladů třídění, definováno kriterium třídění a určeny oblasti třídění podle velikosti částic a sklonu dna koryta.
The reinforcement corrosion is the phenomenon that highly affects the reliability and durability of reinforced concrete structures. From that reason, a lot of researchers in Slovakia and in the world pay their attention to reinforcement corrosion. In the frame of the research work, the reinforced concrete girder bridges were diagnosed and observed. These bridges are influenced by reinforcement corrosion of main girders. The paper is concerned with detection and simulation of corrosion of steel reinforcement in the reinforced concrete. The cracking response of the reinforced concrete beams due to the corrosion effect of the steel reinforcement was analyzed. The effect of corrosion was simulated by the nonlinear numerical analysis using the program ATENA - 2D and 3D module. and Obsahuje seznam literatury
This article presents the numerical modelling of hydrodynamics and sediment transport processes in the seasonal Pathri Rao River, which flows in the Northern part of India. Modelling is made by the coupled application of the hydrodynamic model called TELEMAC-2D and the morphodynamic model called SediMorph. The hydrodynamic model results are validated with the observed data and it has been found that the present model provides reasonable predictions. Likewise, the validation of the morphodynamic model is also presented. For this purpose, the suspended and bed load transport modules are validated separately for four runoff events observed during the investigations. The validation of the former is approached by comparing the depth-averaged suspended transport concentrations against experimental measurements made at the make-shift gauging station and subsequent comparison against experimental measurements. On the other hand, due to non-availability of the observed values on bed load sediment transport, the bed load sediment transport and bed evolution numerical results could not be validated quantitatively and was approached only on qualitative basis. In general, both validations present an acceptable agreement with measurements and scientific facts. Further, this study demonstrates that the coupled TELEMAC-2D/SediMorph system could be used with confidence for practical applications in the Pathri Rao River. and Príspevok obsahuje výsledky numerického modelovania hydrodynamických javov a transportu sedimentov v občasnom toku Pathri Rao, v severnej časti Indie. Procesy boli modelované zdvojenou aplikáciou hydrodynamického modelu TELEMAC-2D a morfodynamického modelu SediMorph. Výsledky modelovania hydrodynamickým modelom boli verifikované s využitím pozorovaných hodnôt; bolo zistené, že model dáva akceptovateľné výsledky. Prezentuje sa tiež verifikácia morfodynamického modelu. Počas epizód odtoku bol transport suspendovaných častíc a častíc transportovaných po dne toku verifikovaný osobitne. Verifikácia transportu suspendovaných častíc bola uskutočnená porovnaním hĺbkovo spriemerovanými koncentráciami suspendovaných častíc s meranými hodnotami na prietokomerných staniciach. Pre nedostatok pozorovaných údajov o dnovom transporte, údaje o ňom a o zmenách morfológie toku mohli byť verifikované len kvalitatívne. Záverom, obe verifikácie dali akceptovateľnú zhodu s výsledkami meraní a existujúcimi vedeckými poznatkami. Okrem toho výsledky štúdie demonštrujú schopnosť zdvojených modelov TELEMAC-2D/SediMorph získavať spoľahlivé výsledky pri aplikácii na rieke Pathri Rao.
Combination of numerical models of deformations and repeated geodetic measurement results provide reliable information on the state of the rock mass in a mining area and support planning and control of the mining operation. The paper describes the concept of integrated monitoring and analysis of rock mass deformation in the Kvannevann iron ore mine (Norway) using sub-level caving (SLC) method. Geodetic control network developed for periodic measurements of surface subsidence and a source of geometrical data for numerical modelling of deformations using finite element method (FEM) has been characterised. Focus is given to the results of initial numeric al analyses with FEM of rock mass deformations due to SLC mining. The results of the modelling provided information on possible extent of deformation zones on the mining ground surface once mining with new method commences., Jan Blachowski and Steinar Ellefmo., and Obsahuje bibliografické odkazy
Uniform flow in compound channels has been studied in terms of a numerical model, called the NKE model. The model uses the three dimensional Navier-Stokes equations in conjunction with the non-linear k-ε turbulence model. The latter is used for the calculation of the Reynolds stress components responsible for the generation of the secondary currents. This model is based on the SIMPLE technique, and computes the six parameters U, V, W, P, k, and ε using wall functions on a Cartesian grid. The NKE model was used to simulate the compound open channel flows of the UK Flood Channel Facility run 080301 (Shiono and Knight, 1989). The Reynolds Stress Model (RSM) of FLUENT was also used as a comparison. The results obtained have shown that the NKE and RSM models can reasonably predict the primary mean velocity and secondary currents. Although agreement is certainly not perfect in every detail, the main features of the flow are reproduced. The bulging of the contours at the bottom corner of the main channel, the inclination of the contours near the free surface towards the channel centre, and the depression of the maximum velocity below the free surface can be seen. These are consistent with the pattern of the secondary flows, which are mainly formed by two vortices, namely the main channel vortex and flood plain vortex. These vortices, which originate near the main channel-flood plain junction, can be reproduced by the NKE and RSM models. and Štúdia pomocou numerického modelu NKF analyzuje ustálený rovnomerný prúd vody v koryte zloženom z kinety a dvoch symetrických beriem so zvislými stranami. Model využíva tri rovnice Naviera- Stokesa a nelineárny k-ε model turbulencie, ktorý simuluje Reynoldsove napätia, zodpovedné za druhotné prúdy. Tento model, založený na tzv. SIMPLE technike, počíta šesť parametrov U, V, W, P, k a ε pri použití stenových funkcií a karteziánskej siete. NKE model simuloval prúdenie, experimentálne pozorované na zariadení UK Flood Channel Facility ako séria č. 080301 (Shiono a Knight, 1989). Model pre Reynoldsove napätia (RSM) z balíka FLUENT bol tiež využitý na porovnanie. Výsledky ukázali, že modely NKE a RSM sú schopné predpovedať ako základné rýchlostné pole, tak aj vyvolané druhotné prúdenia. Aj keď zhoda s experimentom nie je v každom detaile úplná, hlavné znaky rýchlostného poľa sú zobrazené. Na simulácii možno vidieť zaoblenie rýchlostného poľa v rohoch dna hlavného kanála, sklon poľa v blízkosti hladiny smerom do stredu, ako aj pokles maxima rýchlosti pod voľnú hladinu. Tieto efekty sú v súlade s obrazom druhotných prúdov, ktoré sú tvorené hlavne dvoma vírmi - vírom kinety a vírom bermy. Tieto víry, vznikajúce pri spojení kinety s bermou, môžu byť reprodukované modelmi NKE a RSM.
The paper deals with design optimization of a capacitive micromachined switch consisting of a thin membrane suspended over a central conductor. The aim is to achieve as small necessary electrostatic pull-in force as possibble while ensuring fast switching. Optimum parameters are searched using fast linear and nonlinear beam models verified by the finite element method. and Obsahuje seznam literatury
In this paper the numerical approximation of a two dimensional aeroelastic problem is addressed, where nonlinear effects are considered. For the flow model we use the Navier-Stokes equations, spatially discretized by the FE method and stabilized with a modification of the Galerkin Least Squares (GLS) method. The motion of the computational domain is treated with the aid of the Arbitraty Lagrangian Eulerian (ALE) method. The structure model is considered as a solid body with two degrees of freedom (bending and torsion). The motion is described with the aid of a system of nonlinear differential equations and coupled with the flow model by the strongly coupled algorithm. and Obsahuje seznam literatury
Study is focused on the numerical modeling of fly-ash transport in three sands, which was experimentally studied in the laboratory. Sands were packed in glass cylinders with diameter of 5.52 cm and height of 18 cm. Sands were also packed in plastic cylinders with diameter of 30 cm and height of 40 cm. The fly-ash and pulse infiltrations were applied on the top of all cylinders. Visually observed and gravimetrically evaluated fly-ash migration in small cylinders corresponded to fly-ash mobility in large columns detected using the SM400 Kappameter. The HYDRUS-1D code was used to simulate observed fly-ash transport. Parameters of soil hydraulic functions were either obtained using the Tempe cells and the RETC program or estimated using numerical inversion of transient water flow data measured in both types of columns using HYDRUS-1D. Parameters characterizing colloid transport in sands were then estimated from the final fly-ash distribution in sandy columns using attachment/detachment concept in HYDRUS-1D. Fly-ash mobility increased with increasing sand particle sizes, e.g. pore sizes. Particle sizes and pore water velocity influenced the attachment coefficient, which was calculated assuming filtration theory. The same longitudinal dispersivity, sticking efficiency and detachment coefficient sufficiently characterized fly-ash behavior in all sands. and Studie je zaměřena na numerické modelování transportu úletového popílku ve třech píscích, který byl experimentálně studován v laboratoři. Písky byly nahutněny ve skleněných válcích o průměru 5,52 cm a výšce 18 cm. Písky byly také nahutněny v plastových válcích o průměru 30 cm a výšce 40 cm. Na povrchu válců byly aplikovány jednorázové infiltrace vody s popílkem. Migrace úletového popílku pozorovaná vizuálně a zjištěná gravimetricky v malých válcích odpovídala mobilitě úletového popílku detekované Kappametrem SM400 ve velkých válcích. Pozorovaný transport úletového popílku byl simulován programem HYDRUS-1D. Parametry hydraulických funkcí byly získány buď pomocí Tempských cel a programu RETC nebo odhadovány numerickou inverzí transientních data měřených na obou typech válců programem HYDRUS-1D. Parametry charakterizující transport koloidů v píscích byly potom odhadovány z konečné distribuce úletového popílku v písčitých sloupcích užitím konceptu attachment/detachment (připojení/odpojení) v programu HYDRUS-1D. Mobilita úletového popílku se zvyšovala se zvyšující se velikostí písčitých zrn, tj. s velikostí pórů. Velikost zrn a pórová rychlost ovlivnila depoziční (attachment) koeficient, který byl počítán na základě filtrační teorie. Stejné hodnoty podélné disperze, efektivity blokování (sticking efficiency) a mobilizačního (detachement) koeficientu charakterizovaly chování úletového popílku ve všech píscích.
The contribution presents a mathematical and numerical investigation of the Atmospheric Boundary Layer (ABL) flow over the real configuration given by a brown coal mine and coal depot in North Bohemia. The influence of various types of protective
obstacles (as forest blocks, tree-line, walls) on the reduction of dustiness has been studied.
The mathematical models are based on the system of Reynolds Averaged Navier-Stokes (RANS) equations for a viscous incompressible flow. The full system of RANS equations in conservative form was solved using finite-volume explicit scheme and artificial compressibility method. A simple algebraic turbulent model was used for the closure of the basic system of equations. Additional transport equation for passive pollutant has been considered in order to study the pollution dispersion over the
complex 3D topography. The forest stand is simulated using the additional source term in the momentum equations which depends on the local velocity magnitude, the characteristic area of the obstacle and on the drag coefficient. and Obsahuje seznam literatury
The article deals with the numerical simulation of unstable, incompressible flows with stratifications. The mathematical model is based on the Boussinesq approximation of the Navier-Stokes equations. The flow field in the towing tank with a moving cylinder is modeled for wide range of Richardson numbers. The obstacle is modeled via appropriate source terms. The resulting set of PDE is then solved by the fifth oorder WENO scheme, or by a second order finite volume AUSM MUSCL scheme. Both schemes are combined with the artificial compressibility method in dual time. and Obsahuje seznam literatury