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
Flow of particles suspended in a fluid can be found in numerous industrial processes utilizing sedimentation, fluidization and lubricated transport such as food processing, catalytic processing, slurries, coating, paper manufacturing, particle injection molding and filter operation. The ability to understand rheology effects of particulate flows is elementary for the design, operation and efficiency of the underlying processes. Despite the fact that particle technology is widely used, it is still an enormous experimental challenge to determine the correct parameters for the process employed. In this paper we present \mbox{2-dimensional} numerical results for the behavior of a particle based suspension and compare it with analytically results obtained for the Stokes-flow around a single particle.
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
We deal with the numerical simulation of a flow of solid-liquid-gas slurries with the virtual mass effect. The governing systmn of equations is strongly nonlinear hyperbolic with nonconservative terms. We propose a numerical scheme which belongs to the class of finite volume methods. In order to increase the order of convergence we apply a higher order reconstruction technique. Several numerical examples demonstrating the efficiency of the schemes are presented. and Obsahuje seznam literatury
The article deals with the numerical solution of transitional flows. The single-point k-kL-ω model of [7] based on the use of a laminar kinetic energy transport equation is considered. The model doesn‘t require to evaluate integral boundary layer parameters (e.g. boundary layer thickness) and is therefore suitable for implementation into codes working with general unstructured meshes. The performance of the model has been tested for the case of flows over a flat plate with zero and non-zero pressure gradients. The results obtained with our implementation of the model are compared to the experimental data of ERCOFTAC. and Obsahuje seznam literatury
This study deals with the numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract and the flow can represent a model of airflow coming from the trachea, through the glottal region with periodically vibrating vocal folds to the human vocal tract.
The flow is described by the system of Navier-Stokes equations for laminar flows. The numerical solution is implemented using the finite volume method (FVM) and the predictor-corrector MacCormack scheme with Jameson artificial viscosity using a grid of quadrilateral cells. Due to the motion of the grid, the basic system of conservation laws is considered in the Arbitary Lagrangian-Eulerian (ALE) form.
The authors present the numerical simulations of flow fields in the channel acquired from a program developed exclusively for this purpose. The numerical results for unsteady flows in the channel are presented for inlet Mach number M∞ = 0.012, Reynolds number Re∞ = 5x103 and the wall motion frequency 100 Hz. and Obsahuje seznam literatury
The paper deals with a modeling of a flow in hydraulic parts of a turbo machine operating in a pump and in a turbine mode. The results are Q-H (Q-Y) performance characteristics of the pump operating in both modes. An important piece of knowledge is a shift of the pump‘s and turbine‘s BEP and the change of specific speeds of the turbo machine in a pump and in a turbine mode, which emerges from it. The goal of this paper was to find a shift of pump‘s and turbine‘s BEP and to obtain information about hydraulic efficiency of the pump operating in a pump and turbine mode. Anyway the aim of CFD simulation is to evaluate Q-H (Q-Y) characteristic from the point of view of a stability of Q-H curve. The analysis of flow patterns in the impeller and in the vane diffuser in a pump and turbine mode is a valuable contribution to the topic of a hydraulic interaction between an impeller and a vane diffuser. and Obsahuje seznam literatury
The article presents a numerical model of a coupled electro-magneto-mechanical system - an electromagnet exposed to vibration of a yoke. Operation of a multi-physical (an electro-magneto-mechanical) model is simulated under different working and excitation conditions and a response of the system is analyzed. Simscape, a tool of MATLAB programming environment, is used for numerical analysis of the problem. It is shown, that there exists a combination of operation parameters, which can lead to a substantial attenuation ot the yoke vibration. Furthermore, there exists a critical magnitude of the current, which corresponds to a permanent attraction of the yoke to the electromagnet. An analysis of electormagnet‘s initialization shows an induction of high voltages in electric circuit, which can damage the electromagnet and need to be avoided by a proper choice of parameters. and Obsahuje seznam literatury
This contribution deals with the modern finite volume schemes solving the Euler and Navier-Stokes equations for transonic flow problems. We will mention the TVD theory for first order schemes and some numerical examples obtained by 2D central and upwind schemes for 2D transonic flows in the GAMM channel or through the SE 1050 turbine of Škoda Plzeň. The TVD MacCormack method is extended to a 3D method for solving flows through turbine cascades. Numerical examples of unsteady transonic viscous (laminar) flows through the DCA 8% cascade are also presented for Re = 4600. Next, a new finite volume implicit scheme is presented for the case of unstructured meshes (with both triangular and quadrilateral cells) and inviscid compressible flows through the GAMM channel as well as the SE 1050 turbine cascade.