|
|
Developing a coupled CFD solver for mass, momentum and heat transport in catalytic filters
Hlavatý, Tomáš ; Isoz, Martin ; Kočí, P.
Using catalytic filters (CF) in automotive exhaust gas aftertreatment decreases the system heat losses and facilitates the CF regeneration. On the other hand, the CF overall performance is strongly dependent on the catalytic material distribution within it. In the present work, we aim to provide a computational framework to study the dependence of the CF characteristics, i.e. the pressure loss and the conversion of gaseous pollutants, on the catalyst distribution. Previously, we built an isothermal computational fluid dynamics (CFD) model of the flow and conversion of gaseous pollutants inside the CF. However, the reactions occurring inside the CF are exothermic and the assumption of constant temperature proved to be too restricting for real-life applications of the developed isothermal CFD model. Thus, in this work, we extend the framework by the enthalpy balance, which requires combining all the transport equations (mass, momentum and enthalpy) in a single solver. The new and more general solver provides results in good agreement with a well established (1+1)D channel model calibrated on experimental data. Furthermore, it allows studying more complex device-scale geometries of laboratory CF samples.
|
|
|
Recent improvements in CFD solver for fully coupled particle-laden flows
Šourek, M. ; Isoz, Martin
While new methods combining the computational fluid dynamics (CFD) and the discrete element method (DEM) have been developed to simulate freely moving solid particles, they tend to be focused on simulations with spherical particles only. Here, we present a strongly coupled CFD-DEM solver capable of simulating movement of arbitrarily-shaped particles dispersed in a fluid. The particles are assumed to be large enough to affect the fluid flow and distributed densely enough to come into contact with both the boundaries of the computational domain and with each other. In this paper, we will focus on the recent improvements of our solver, specifically, in the areas of (i) inclusion of solid bodies into the computational domain, (ii) general CFD-DEM coupling algorithm, and (iii) code parallelization and practical usability.
|
|
|
Increasing Ejector Efficiency via Diffuser Shape Optimization
Kubíčková, Lucie ; Isoz, Martin ; Haidl, Jan
An ejector is a technologically simple and yet wide-application fluid machine. While it has favorable characteristics for a signifficant number of technological processes, its main downside is probably its high operational energy demands. The present paper is an initial result of an ongoing research aimed at improving energy e ciency of the ejector via optimization of its geometry. In the paper, we focus mostly on presenting a general multi-objective optimization framework usable for an ejector shape optimization. The approach applicability is illustrated on a simpli ed problem comprising only a single phase flow in an ejector mixing tube and diffuser. Nevertheless, the achieved simulation and optimization results are validated against experimental data. The proposed optimization method itself is based on multi-objective evolutionary algorithms (MOEAs) combined with computational fluid dynamics (CFD) for evaluation of the vector-valued objective function.
|
|
|
Parametric Generator of Heat Exchanger Tube Bundle Mesh for OpenFOAM
Petrů, Martin ; Juřena, Tomáš (referee) ; Turek, Vojtěch (advisor)
This thesis deals with the basics of computational fluid dynamics (CFD), the reasons for its use, and the related necessity to create computational meshes. The next part of the thesis focuses on assessing the quality of computational meshes and, briefly, on computational methods of CFD. The available mesh generators are also compared, and an overview of meshing capabilities is provided. The following is basic information about the OpenFOAM software and its capabilities, in particular the creation of meshes using the blockMesh application. The following part of the thesis is focused on the description of the developed application and its functions for generating a high-quality computing mesh of a tube bundle heat exchanger for the OpenFOAM software. In conclusion, a steady flow simulation verifies the correctness of the created mesh and its sufficient quality.
|
|
|
Development of CFD solver for four-way coupled particle-laden flows
Šourek, M. ; Isoz, Martin
Computational uid dynamics (CFD) simulations containing freely moving bodies are still a challenging topic. More so, if the bodies are large enough to a_ect the uid ow and distributed\ndensely enough to come in contact both with the boundaries of the computational domain and with each other. In this work, we concentrate on the topic of simulation of (i) irregular bodies\nwith ow-induced movement and contact with computational domain boundaries taken into account, and (ii) bodies entrained by the uid and coming in contact not only with the domain\nboundaries but also with each other. The developed modeling approach is based on the hybrid _ctitious domain-immersed boundary method extended by the discrete element method. The\npresent contribution is focused on presentation of simulation principles and results of initial benchmark cases.
|
|
|
POD-DEIM-based model order reduction for four-way coupled fluid-solid flows
Isoz, Martin ; Šourek, M.
Proper orthogonal decomposition (POD) and discrete empirical interpolation method (DEIM) have become established tools for model order reduction in simulations of fluid flows. However, including moving solid bodies in the computational domain poses additional issues with respect to the fluid-solid coupling and to the solution of the movement of the solids. Still, it seems that if the hybrid ctitious domain-immersed boundary method is used to include the solids in the flow domain, POD-DEIM based approaches may be extended for four-way coupled particleladen flows. The present work focuses on the construction of POD-DEIM based reduced order models for the aforementioned flows.
|
|
|
Geometrically realistic macro-scale model for multi-scalesimulations of catalytic filters for automotive gasaftertreatment
Hlavatý, Tomáš ; Isoz, Martin ; Plachá, M. ; Šourek, M. ; Kočí, P.
This paper is part of a research focused on simulating (i) the catalytic conversion of environment endangering gases, and (ii) trapping of the particulate matter in automotive exhaust gas aftertreatment. Historically, the catalytic conversion and the filtration of soot particles were performed in independent devices. However, recent trend is to combine the catalytic converter and soot filter into a single device, the catalytic filter. Compared to the standard two-device system, the catalytic filter is more compact and has lower heat losses. Nevertheless, it is highly sensitive to the catalyst distribution. This study extends our recently developed methodology for pore-scale simulations of flow, diffusion and reaction in the coated catalytic filters. The extension consists of enabling data transfer from macro- to pore-scale models by preparing geometrically realistic macro-scale CFD simulations. The simulation geometry is based on XRT scans of real-life catalytic filters. The flow data from the newly developed macro-scale model are mapped as boundary conditions into the pore-scale simulations and used to improve the estimates of the catalytic filter filtration efficiency.
|
|
| |
|
|
Preliminary aerodynamic analysis of remotely controlled model with jet propulsion
Novák, Ondřej ; Zikmund, Pavel (referee) ; Popela, Robert (advisor)
This bachelor´s thesis deals with aerodynamic analysis of unmanned aircraft and subsequent changes to design of wing, its position and wing-fuselage junction. In this work emphasis is laid on flow separation, its interaction with other flow structures and its influence on aerodynamic properties. The goal of these changes to the aircraft is ensuring sufficient stability and controllability in low as well as high angle of attack flight. AVL, XFLR5 and CFD methods were used in the thesis. In case of inaccuracy of CFD calculation, two backup wing related modifications were prepared.
|
|
|
Sports car rear wing numerical optimization
Feldová, Petra ; Rudolf, Pavel (referee) ; Štefan, David (advisor)
This master’s thesis is focused on optimization of rear wing of sport car by using open-source software. The optimization of 2D profile of the rear wing is present in this thesis. Python environment was chosen for optimization and evolutionary algorithm was is used as optimization function. This algorithm is further connected to Xfoil software, which is computing aerodynamic characteristic. The ratio of the lift and drag coefficients (C_L/C_D) is chosen as parameter which considers the aerodynamic efficiency. The CFD computation of flowing around the whole car is provided in open-source software OpenFOAM. . The profile optimization results to approximately 7.9 % raise of the parameter C_L/C_D, in the same wing stability. The main benefit of this work is to use open-source software for the optimization and CFD analysis, which in future might save company’s resources by not buying expensive commercial software licenses.
|
guest ::
