1. Numerical optimisation of a wastetoenergy plant's operating parameters using CFDMiran Kapitler, Niko Samec, Filip Kokalj, 2011, izvirni znanstveni članek Opis: The combustion process for using municipal solid waste as a fuel within a waste to energy plant calls for a detailed understanding of the following phenomena. Firstly, this process depends on many input parameters such as proximate and ultimate analyses, the season of the year, primary and secondary inlet air velocities and, secondly, on output parameters such as the temperatures or massflow rates of the combustible products. The variability and mutual dependence of these parameters can be difficult to manage in practice. Another problem is how these parameters can be tuned to achieving optimal combustible conditions with minimal pollutant emissions, during the plantdesign phase. in order to meet these goals, a wastetoenergy plant with bed combustion was investigated by using computational fluiddynamics approach. The adequate variable input boundary conditions based on the real measurement are used and the whole computational work is updated using real plant geometry and the appropriate turbulence, combustion, or heat transfer models. The operating parameters were optimized on output parameters through a tradeoff study. The different operating conditions were varied and the combustible products were predicted and visualized. Finally, the response charts and matrix among the input and output parameters during the optimization process are presented, which monitored the dependence among these parameters. Ključne besede: municipal solid waste, bed combustion, computational fluid dynamics, numerical optimization, goal driven optimization, tradeoff study, parameters correlation Objavljeno: 01.06.2012; Ogledov: 1037; Prenosov: 57 Celotno besedilo (1,83 MB) Gradivo ima več datotek! Več...

2. Laminar flow of a shearthickening fluid in a 90° pipe bendJure Marn, Primož Ternik, 2006, izvirni znanstveni članek Opis: The nonNewtonian fluid flow in a sharp 90 curved pipe is studied numerically to obtain the pressure loss coefficient prompted by disagreement between the existing empirical correlations and results obtained by computer codes. This disagreement results from presumption of fully developed flow throughout the curvature (correlations) while the actual flow is partially developed for the Newtonian and sharp 90 curved bend nonNewtonian flows, and fully developed for slightly bent 90 curvature nonNewtonian flow. The Quadratic model is employed to accommodate the shearthickening behavior of an electrostatic ash and water mixture. Numerical results are obtained for different values of Reynolds number. Finally, results for local pressure loss coefficient are compared with values obtained for the Power law rheological model. Ključne besede: shearthickening fluid, fluid dynamics, rheological model, pipe bend flow, numerical modelling, pressure losses Objavljeno: 30.05.2012; Ogledov: 1160; Prenosov: 57 Povezava na celotno besedilo 
3. Intake system design procedure for engines with special requirementsPrimož Pogorevc, Breda Kegl, 2006, izvirni znanstveni članek Opis: Intake manifolds provide fresh air to internal combustion engines and have a major effect on their performance. Therefore, many investigations are related to their design in order to improve the charging efficiency and to achieve theuniform distribution of fresh air among the engine cylinders. This paper deals with the design procedure of a cheap multipoint injection intake system,adapted to a racing car engine. Some special demands had to be taken into consideration. The intake manifold must contain the imposed constraint for the airflow in the shape of a single circular restrictor placed between the throttle and the engine to limit its power. The flow and the pressure lossreduction in the engine intake region were investigated with computationalfluid dynamics software. Two different geometries of the intake manifold were taken into consideration. On the basis of the numerically obtained threedimensional results, a mathematical model of the engine with a more appropriate intake was made in the engine simulation code in order to anticipate its characteristics. The intake system was designed, practically manufactured, and tested in the laboratory. The experimental results confirmednumerical predictions, justifying the simple and relatively quick design procedure for the intake system. Ključne besede: internal combustion engines, intake manifold, computational fluid dynamics, experiment Objavljeno: 30.05.2012; Ogledov: 1170; Prenosov: 71 Povezava na celotno besedilo 
4. Combustion simulation in the secondary chamber of a pilotscale incineratorNiko Samec, Filip Kokalj, JyhYan Chen, 2007, izvirni znanstveni članek Opis: A numerical analysis of combustion in the secondary chamber (thermoreactor) ofa twostage pilot scale incinerator using computational fluid dynamics (CFD)is presented in detail. Various versions of the CFD program package CFX were used, which offer different combustion models for specific types and forms of combustion processes. The present study was focused on those physicalconditions that assure complete combustion, that is, temperature, residence time, and turbulent mixing. The selection of an appropriate combustion model was based on a comparison of the numerical results and experimental values of some combustion macro parameters in a thermoreactor. Combustion models based on onestep bimolecular chemical reaction and models based on multistep reactions were used. These models enabled a more detailed prediction of the combustion process in the secondary chamber of a pilotscaleincinerator. The products of incomplete combustion that are significantly important for the designing and optimization of combustion devices can be predicted by applying multistep reaction models more accurately, especially in a transient regime of combustion. Ključne besede: waste incineration, numerical modeling, combustion models, incinerator chamber, CFX, CFD, computational fluid dynamics Objavljeno: 31.05.2012; Ogledov: 1378; Prenosov: 46 Povezava na celotno besedilo 
5. The influence of rotating domain size in a rotating frame of reference approach for simulation of rotating impeller in a mixing vesselMatej Zadravec, Sani Bašič, Matjaž Hriberšek, 2007, izvirni znanstveni članek Opis: This paper presents simulation of rotating impeller in a mixing vessel by means of Computational Fluid Dynamics (CFD). A special emphasis is devoted to the study of influence of the choice of numerical model for simulation of rotation of impeller when mixing a Newtonian fluid in a vessel equipped with Rushton impeller, and operating under turbulent flow conditions. In order to determine the best simulation approach experimental validation of the selected problem is done by means of Particle Image Velocimetry (PIV) system. When using the rotating frame of reference approach, the stirring vessel geometry has to be split into a stationary and rotating part, and the questionarises where to position the interface between both regions in order to avoid numerical errors, originating in numerical approximations at the interface. To answer this question, a comparison between the CFD based numerical results and experimental results, was made. Ključne besede: fluid mechanics, turbulent flow, Computational Fluid Dynamics, Particle Image Velocimetry, rotating frame of reference Objavljeno: 31.05.2012; Ogledov: 1251; Prenosov: 34 Povezava na celotno besedilo 
6. Aerodynamic analysis of an oscillating airfoil in a powerextraction regime using the compressible NavierStokes equations with efficient and accurate lowspeed preconditioningJernej Drofelnik, 2012, diplomsko delo Opis: A wing that is simultaneously heaving and pitching may extract energy from an oncoming air flow, thus acting as turbine. The purpose of this study was to analyse the relationship between the aerodynamics and the theoretical performance of this device by means of timedependent
laminar flow simulations performed with a research compressible finite volume NavierStokes solver COSA. In presented analyses, which confirm the findings of another
independent study, the efficiency of the power extraction of this device can be of the order of 35 %, and such an efficient operating condition is characterized due to the favourable effects of a strong dynamic stall.
This study is a part of a wider research programme of Dr. Campobasso’s group at University of Glasgow, aiming to develop a generalpurpose computational framework for
unsteady aerodynamic and aeroacoustic wind energy engineering. In view of aeroacoustic applications, the developed flow solver uses the compressible formulation of the NavierStokes equations with carefully optimized lowspeed preconditioning. To demonstrate the modeling capabilities, the accuracy and the high computational performance of the developed lowspeed preconditioning technology, the unsteady aerodynamics of the energyextracting device is simulated by using a computationally challenging freestream Mach number of 0.001. A mixed preconditioning strategy that maintains both the nominal accuracy and the computational efficiency of the solver also for timedependent lowspeed problems is presented. A fundamental element of novelty of this study is a thorough assessment of the proposed approach partly based on the challenging and realistic problem associated with the oscillating wing device. Ključne besede: Lowspeed preconditioning, compressible multigrid NavierStokes solver, energyextracting oscillating wing, computational fluid dynamics. Objavljeno: 06.07.2012; Ogledov: 1720; Prenosov: 84 Celotno besedilo (2,40 MB) 
7. BEM for the twodimensional plane compressible fluid dynamicsLeopold Škerget, Niko Samec, 2005, izvirni znanstveni članek Opis: In this study, the boundary element method, which has been established for theviscous incompressible fluid motion, is modified and extended to capture the compressible fluid state. The velocityvorticity formulation of the time dependent set of equations is employed, where the kinematics is given with thePoisson velocity vector equation, while the kinetics is represented with the vorticity transport equation, and the pressure field function is governed by the Poisson pressure scalar equation. The method is applied to consider buoyancy driven flow in closed cavity, differentially heated under large temperature gradients. The ideal gas law is used and viscosity is given by Sutherland law. Ključne besede: fluid mechanics, compressible viscous fluid, natural convection, boundary element method, fluid dynamics Objavljeno: 01.06.2012; Ogledov: 945; Prenosov: 60 Povezava na celotno besedilo 
8. The wavelet transform for BEM computational fluid dynamicsJure Ravnik, Leopold Škerget, Matjaž Hriberšek, 2004, izvirni znanstveni članek Opis: A wavelet matrix compression technique was used to solve systems of linear equations resulting from BEM applied to fluid dynamics. The governing equations were written in velocityvorticity formulation and solutions of the resulting systems of equations were obtained with and without wavelet matrix compression. A modification of the Haar wavelet transform, which can transformvectors of any size, is proposed. The threshold, used for making fully populated matrices sparse, was written as a product of a user defined factor and the average value of absolute matrix elements values. Numerical tests were performed to assert, that the error caused by wavelet compression depends linearly on the factor , while the dependence of the error on the share of thresholded elements in the system matrix is highly nonlinear. The results also showed that the increasing nonlinearity (higher Ra and Re numbervalues) limits the extent of compression. On the other hand, higher meshdensity enables higher compression ratios. Ključne besede: fluid mechanics, computational fluid dynamics, boundary element method, wavelet transform, linear systems of equations, velocity vorticity formulation, driven cavity, natural convection, system matrix compression Objavljeno: 01.06.2012; Ogledov: 1278; Prenosov: 58 Povezava na celotno besedilo 
9. Natural convection flows in complex cavities by BEMLeopold Škerget, Matjaž Hriberšek, Zoran Žunič, 2003, izvirni znanstveni članek Opis: A numerical method for the solution of NavierStokes equations is developed using an integral representation of the conservation equations. The velocity vorticity formulation is employed, where the kinematics is given with the Poisson equation for a velocity vector, while the kinetics is represented with the vorticity transport equation. The corresponding boundarydomain integral equations are presented along with discussions of the kinetics and kinematics of the fluid flow problem. THE BEM formulation is developed and tested for natural convection flows in closed cavities with complex geometries. Ključne besede: fluid dynamics, natural convection, boundary element method, differential equations, closed cavity Objavljeno: 01.06.2012; Ogledov: 764; Prenosov: 54 Povezava na celotno besedilo 
10. Multifunctional composites by highpressure spray processesEckhard Weidner, Marcus Petermann, Željko Knez, 2003, pregledni znanstveni članek Opis: A series of spraying processes designed to generate powders and composites using supercritical fluids have been proposed in the past 15 years. In this review, thermo and fluiddynamic aspects and engineering principles are discussed and advantages of such technologies are demonstrated. These new techniques display convincing advantages, producing competitive highquality products with tailormade properties. Initial industrial applications have been achieved in the production of food products and finechemicals. Ključne besede: chemical processing, high pressure technology, micronization, supercritical fluids, particles, powder generation, thermodynamics, fluid dynamics, PGSS Objavljeno: 01.06.2012; Ogledov: 1532; Prenosov: 61 Povezava na celotno besedilo 