Wyniki wyszukiwania - Biblioteka Nauki

1

Numerical analysis of influence of streamline rudder on screw propeller efficiency

100%

Abramowski T. , Handke J. , Szelangiewicz T.

Polish Maritime Research

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2010

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tom nr 2

18-22

EN

During designing the ship its designer tends to obtain as high as possible efficiency of ship propulsion system. To this end on certain ships additional elements such as: nozzles, half-nozzles or suitably profiled fins attached to underwater part of ship’s hull before screw propeller, are applied (sometimes they are intended for the mitigating of vibration resulting from operation of screw propeller). Another device which affects operation of screw propeller is streamline rudder capable of improving its efficiency (most of the transport ships is fitted with single screw propeller and streamline rudder placed behind it). In this paper the influence of streamline rudder on screw propeller efficiency has been examined with the use of numerical methods of fluid dynamics (CFD).The obtained results indicate a very favourable influence of the rudder on screw propeller efficiency. Research in this area is continued and its results concerning impact of particular geometrical parameters of rudder on screw propeller efficiency, will be presented in the future.

2

Symulacja numeryczna CFD na przykładzie modelu zbiornika retencyjnego Canalis w fazie opróżniania

80%

Rzepka A. , Mrowiec M. , Nowak A. I.

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2010

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tom Nr 5

38-42

PL

W artykule omówiono kwestie wykorzystania nowoczesnego narzędzia służącego do analiz między innymi z zakresu numerycznej mechaniki płynów (CFD). Jest nim komercyjny pakiet programów Ansys Fluent. W badaniach wykorzystano model fizyczny zbiornika retencyjnego o konstrukcji rurowej – Canalis, dla kanalizacji deszczowej oraz jego odpowiednik numeryczny. Niniejszy artykuł jest drugą częścią dotyczącą analizy pracy tego zbiornika i przedstawia wybrane elementy porównawcze dla fazy opróżniania. Jednym z głównych celów podjętych działań jest wykazanie zaawansowanych możliwości efektywnego wykorzystania modelowania numerycznego do analizy działania omawianego obiektu hydraulicznego. Na uwagę, oprócz użytego narzędzia, zasługuje nowatorska droga uchwycenia problemu, która polega w głównej mierze na uwzględnieniu w matematycznym opisie modelu trójwymiarowości zachodzących zjawisk, transportu masy (wody i powietrza) w oparciu o model wielofazowy Volume-of-Fluid oraz na przyjęciu jednego z modeli turbulencji (k-.). Nacisk kładziono na obserwacje współistnienia ruchu cieczy o charakterze swobodnym z ruchem ciśnieniowym oraz fazy przejściowe, ponieważ są to zjawiska najtrudniejsze do uchwycenia. Uwagę skupiał kształt i miejsce wystąpienia granicy międzyfazowej (powierzchni swobodnej) w analogicznych momentach przebiegu zjawiska w każdym z modeli. Drugim kryterium porównawczym było zestawienie punktów czasowych wystąpienia danej charakterystycznej formy przepływu cieczy w obydwu obiektach. W procesie walidacji dowiedzione zostało uzyskanie wysokiej zgodności wyników CFD z rezultatami fizycznymi.

EN

This paper discusses an application of the computational fluid dynamics (CFD) software to solve the practical engineering problem involving the drainage system. Particularly, behaviour of the tubular type stormwater storage device (called Canalis) is analysed in details. The second part of the analysis of working tank deals with the emptying stage. The main aim of this research is to present an application of the commercial CFD software (Ansys Fluent) for the modelling of the fluid flow phenomena within the tubular type stormwater tank as well as its experimental conformity. This approach allows one to eliminate numerous simplifications commonly adopted when the hydraulic performance of the storage reservoir is modelled by Saint-Venant equation. The three-dimensional model of the tubular storage tank presented in the paper generally takes into consideration the multiphase flow with free surface (air-water) defined by Volume-of-Fluid formulation and two equation turbulence model. During numerical simulations some attention was paid to observe the transition between the free surface and pressurized flows. This transition is generally the most difficult (even if possible) to be traced using traditional simplified methods. The developed numerical model has been validated experimentally using a scaled lab model of the storage tank. The numerical results compared with the filmed experiment demonstrate very good agreement.

3

Zastosowanie obliczeniowej mechaniki płynów do wyznaczania współczynnika przejmowania ciepła na drodze konwekcji dla obudowy silnika indukcyjnego

80%

Lefik M. , Komęza K.

Zeszyty Naukowe. Elektryka / Politechnika Łódzka

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2012

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tom z. 124

167-175

PL

W artykule opisano metodę wyznaczania współczynnika przejmowania ciepła dla użebrowanej obudowy silnika indukcyjnego. Przedstawiono sposób tworzenia modelu obliczeniowego oraz wyniki obliczeń tego współczynnika. Ponadto przedstawiono wyniki obliczeń cieplnych weryfikujących poprawność wyznaczenia współczynnika przejmowania.

EN

Thermal calculations are an important element of the design and optimization of induction motors due to their use in different operating conditions. These calculations are more frequently done using field methods, based on numerical solution of differential equations of the Fourier-Kirchhoff [1], [2], [3]. In this method, the main problem is to determine a boundary conditions. The most widely used in the Newton boundary condition requires knowledge of the heat transfer coefficient. The paper describes a method of calculations the convective heat transfer coefficient for finned induction motor housing. This method is based on computational fluid dynamics (CFD). A computational model and the results of calculations of this coefficient are presented. Moreover, the results of thermal calculations that verify the convective heat transfer coefficient calculations are shown.

4

CFD computation of the savonius rotor

80%

Rogowski K. , Maroński R.

Journal of Theoretical and Applied Mechanics

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2015

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tom Vol. 53 nr 1

37--45

EN

In this paper, Computational Fluid Dynamics (CFD) analysis of a two-dimensional two- -bucket Savonius rotor, using ANSYS Fluent solver, is presented. Computational methods of fluid dynamics are used to estimate the aerodynamic forces acting on the rotor, the torque and the power extracted by the Savonius rotor. In addition, an analysis of the results for different turbulence models is performed. Numerical investigations are compared with the experiment of the Sandia National Laboratories.

5

Modelling of Influence of Turbulent Transition on Heat Transfer Conditions

80%

Bochon K. , Wróblewski W. , Dykas S.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2008

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tom Vol. 12, No 3-4

173-184

EN

This article deals with the turbulent transition phenomenon modelling and its influence on heat transfer. The purpose of the analyses was to verify the transition modelling implemented in the ANSYS CFX 11 commercial code for popular test cases (low flow speed) described in literature, and then use it for verification of the in-house CFD code (created for compressible flows). The inhouse CFD code has been extended lately for the Conjugate Heat Transfer modelling (CHT) as well, taking into account important flow effects, especially the turbulent transition. A Wilcox k-omega turbulence model with the Low-Reynolds modification was used in the in-house code. The calculations in ANSYS CFX were made using an SST turbulence model and a gamma-theta transition model. A fully turbulent flow was modelled by means of both codes, and the results were compared with the available experimental data. Then, the turbulent transition for several test cases was analysed with ANSYS CFX. Afterwards, the in-house CFD code was verified by means of ANSYS CFX for a higher flow speed (Mach numbers). The CHT modelling was analysed by means of both codes and the results were compared and discussed. The conducted analyses show that the results obtained by means of both codes are comparable, but the turbulence model used in the in-house CFD code is simpler and requires less computation time. A modification of two equations turbulence models can be an alternative for design problems in more developed laminar/turbulent flows.

6

Numerical analysis of volatile organic compounds concentration in A C segmnet vehicle interior – diesel engine exhoust pollution

80%

Dudycz A. , Górniak A. , Janicka A. , Rodak M. , Skrętowicz M. , Trzmiel K. , Włostowski R. , Woźniak J. , Zawiślak M.

Journal of Polish CIMEEAC

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2015

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tom Vol. 10, no 1

45--52

EN

In large cities the number of inhabitants constantly increases. It is caused by economic issues. The evergrowing populations causes more intense traffic and in consequence increase of air pollutions. Topology and roads configuration is conducive to the accumulation of toxic substances. Harmful substances accumulates inside the vehicles interiors which significantly deteriorate microclimate within the cabin. The study aimed to determine the amount of harmful substances getting into the interior of vehicles and their distribution have been presented in this paper.

7

Fishing vessel hull design and towing resistance calculation by the CFD methods

80%

Sugalski K.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2014

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tom nr 40 (112)

27--30

EN

Hull resistance and propulsion calculations are the basis of every ship design. In this paper, application of the computational fluid dynamics are presented together with the results of towing resistance of the model of stern trawler. The practical use of CFD in the preliminary vessels' design process were presented at the stern trawler vessel type.All calculations had been performed in the free CFD software called OpenFOAM. This is set of C++ programming language libraries, designed to solve Navier-Stokes equations.

8

Numerical simulations of gap flow above rotating disk

80%

Wasilczuk F. , Flaszyński P. , Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2015

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tom Vol. 19, No 2

89--100

EN

A rotating disk can be considered a basic configuration for the investigations of the impact of various conditions on the flow through the clearance between the shrouded turbine blade and the casing. Numerical calculations using Fine/Turbo Numeca were conducted to examine the influence of the rotational velocity and the pressure difference across the disk on the flow conditions, especially the mass flow through the clearance. The results were validated using the experimental data. Moreover, the flow field was investigated to reveal the vortices induced in the flow. The calculations showed a significant drop of the mass flow with a rise of the rotation velocity. Additionally, the vortex created upstream of the disk at higher rotation velocities was observed. The phenomenon of separation at the edge of the disk was investigated.

9

A complete design of contra-rotating propellers using the new computer system

80%

Koronowicz T. , Krzemianowski Z. , Tuszkowska T. , Szantyr J. A.

Polish Maritime Research

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2010

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tom nr 1

14-24

EN

The computer system for the complete design of the contra-rotating propellers presented in this article has several common blocks and procedures with the systems for design of single propellers and tandem corotating propellers, presented in detail in the Polish Maritime Research No.1 and No.4 of the Volume 16, 2009. In this article only the blocks and procedures developed specially for the contra-rotating propellers are described. The system is based on the lifting line and lifting surface models and on the Computational Fluid Mechanics methods. The comparative analysis of the contra-rotating propellers and the tandem corotating propellers is included.

10

Numerical model to study the valve overlap period in the Wärtsilä 6L 46 four-stroke marine engine

80%

Lamas M. I. , Rodríguez C. G. , Rebollido J. M.

Polish Maritime Research

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2012

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tom nr 1

31-37

EN

In this paper, a CFD (Computational Fluid Dynamics) analysis was carried out to study the Wärtsilä 6L 46 medium-speed, four-stroke marine engine. For the purpose, the commercial software ANSYS Fluent 6.3 was employed. The aim is to analyze the scavenging of gases, especially during the valve overlap period. Particularly, the pressure, velocity and mass fraction fields were numerically obtained. In order to validate the CFD results, the in-cylinder pressure was successfully compared to experimental measurements for the exhaust, intake and compression strokes of the cylinder operation. This model can be used in future works to improve the performance of these engines because the information provided is very useful to identify regions in which the pressure, velocity or distribution of gases are inadequate. Besides, to compute the quantity of burnt gases which remain inside the cylinder, fresh charge which is expelled through the exhaust valves and study the influence of parameters such as the exhaust and intake pressures, engine speed, cam profile design, etc.

11

Eddy Viscosity Turbulence Models emploed by Computational Fluid Dynamic

80%

Woelke M.

Prace Instytutu Lotnictwa

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2007

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tom Nr 4(191)

92-113

EN

This paper is discussing the advantages and disadvantages of the two-equation eddyviscosity turbulence models employed to carry out computational fluid dynamic analyses. Simulating turbulence by means of numerical methods is one of the most critical problems in modeling fluid flow. The most popular, two-equation eddy-viscosity turbulence models are reviewed in this paper. These models rely on the eddy-viscosity, which according to Boussinesq approach relates Reynolds stress with mean velocity gradients. The consequences of such approach for two-equation models' capabilities in predicting fluid motion are analyzed. Moreover, the current work discusses: (i) Approaches taken to obviate the shortcomings of the Boussinesq assumption; (ii) Performance of the k-ε model and some of its modifications in predicting fluid structure; (iii) Advantages offered by the k-ω model in simulating some class of the flows; (iv) The Shear Stress Transport (SST) model benefiting from the features of the k-ε and k-ω models. This paper discusses the vital problems related to simulating turbulence flows by means of CFD codes.

PL

W pracy zostały przedstawione wady i zalety dwu-równaniowych modeli turbulencji wykorzystujących zagadnienie lepkości burzliwej, które są stosowane w numerycznych analizach mechaniki płynów. Modelowanie przepłwów turbulentnych stanowi jeden z najbardziej skomplikowanych zagadnień w mechanice płynów. Najczęściej stosowane dwu-równaniowe modele turbulencji zostały przedstawione w niniejszej pracy. Modele to wykorzystują lepkość burzliwą, która zgodnie z założeniem Boussinesq`a ustala związek pomiędzy naprężeniami Reynoldsa oraz gradientem prędkości średniej w przepływie turbulentnym. Konsekwencje tego założenia pod względem możliwości analizowania przepływów burzliwych przy pomocy modeli dwu-równaniowych zostały przeanalizowane w pracy. Ponadto w pracy przedyskutowano: (I) modyfikacje założenia Boussinesq`a w celu poprawy jego skuteczności, (II) możliwości modelu k-ε oraz jego modyfikacji do modelowania przepływów turbulentnych, (III) zalety oferowane przez model k-ω w zakresie analiz numerycznej mechaniki płynów, (IV) cechy modelu transportu naprężeń stycznych (Shear Stress Transport - SST) będącego modyfikacją modeli k-ε oraz k-ω. W pracy przedstawiono istotne problemy związane z modelowaniem przepływów turbulentnych przy pomocy numerycznych kodów mechaniki płynów.

12

Wind turbine operation parameter characteristics at a given wind speed

80%

Kamiński Z. , Czyż Z. , Wendeker M.

Advances in Science and Technology. Research Journal

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2014

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tom Vol. 8, nr 22

75--82

EN

This paper discusses the results of the CFD simulation of the flow around Vertical Axis Wind Turbine rotor. The examined rotor was designed following patent application no. 402214. The turbine operation is characterised by parameters, such as opening angle of blades, power, torque, rotational velocity at a given wind velocity. Those parameters have an impact on the performance of entire assembly. The distribution of forces acting on the working surfaces in the turbine can change, depending on the angle of rotor rotation. Moreover, the resultant force derived from the force acting on the oncoming and leaving blades should be as high as possible. Accordingly, those parameters were individually simulated over time for each blade in three complete rotations. The attempts to improve the performance of the entire system resulted in a new research trend to improve the performance of working turbine rotor blades.

13

Determination of the drag coefficient high performance electric vehicle

80%

Danek W.

Modelowanie Inżynierskie

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2014

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tom T. 21, nr 52

36--41

EN

In the article there is presented the process of creating a numerical model aimed at analyzing the aerodynamic properties of a wheeled vehicle MuSHELLka involved in the cycle of the Shell Eco Marathon competition. This analysis was carried out in ANSYS CFX software and it was aimed at determining the drag coefficient of the vehicle and detecting places that produced large flow disturbances.

PL

W artykule przedstawiony został proces wykonywania modelu numerycznego przeznaczonego do wyznaczania własności aerodynamicznych pojazdu kołowego MuSHELLka biorącego udział w cyklu zawodów Shell Eco Maraton. Analizy numeryczne zostały przeprowadzone w oprogramowaniu ANSYS CFX i były zorientowane na wyznaczenie współczynnika oporu aerodynamicznego pojazdu oraz określenie miejsc, które generują największe zakłócenia przepływu.

14

Snizenie stoimosti ziznennogo cikla skvazinnyh nasosov ECV dla vody

80%

Tverdohleb I. , Kostuk A. , Knazeva E. , Solodcenkov V.

|

2008

|

tom Z. 10, Vol. 2

379-386

EN

Current report describes the works executed under the program of modernization of submersible borehole pumps for water. The main aim of this project is to reduce the Life Cycle Cost of borehole pumps for water. The project consists of two parts - developing of new electric motors and design of new pumps. Two main stages of developing of electric motors and new pump are described in this report. For developing pumps modern methods of numerical flow simulations with using ANSYS CFX11 program were used.

15

Hydrodynamic Analysis of Trimaran Vessels

80%

Javanmardi M. R. , Jahanbakhsh E. , Seif M. S. , Sayyaadi H.

Polish Maritime Research

|

2008

|

tom nr 1

11-18

EN

Trimaran vessels are developed for different applications and hydrodynamic behavior of such vessels is different than usual mono-hulls. In this paper hydrodynamic resistance and maneuvering of a trimaran with Wigley body form are investigated. The effects of outriggers position in four different longitudinal and two transverse locations are studied. For hydrodynamic simulations a CFD code has been developed and used. This code is capable for simulating three dimensional, time dependent, two phases, viscous flow coupled with rigid body motion. Formulation and solution algorithm are described in detail. Different case studies have been performance and numerical results have shown good agreement with experimental data. Based on resistance and maneuvering simulation of the trimaran vessels different conclusion are made. The results show that positions of outriggers have great effect on resistance and maneuverability of trimaran. The present method can be further employed to investigate other hydrodynamic qualities of trimaran vessels.

16

Short review of the CFD activities in Poland

80%

Kazimierski Z.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

1998

|

tom Vol. 2, No 2

199-204

EN

Computational fluid dynamics is being developed at several universities and scientific centres in Poland. These centres are considered and a general description of CFD activities is provided. It should be emphasised that the centres mentioned are only the best known ones. The information provided has been prepared in co-operation with the responsible scientists and is authorised by them. Therefore the form of topics description is not uniform.

17

Critical review of propeller performance scaling methods, based on model experiments and numerical calculations

80%

Bugalski T. , Streckwall H. , Szantyr J. A.

Polish Maritime Research

|

2013

|

tom nr 4

71--79

EN

The article presents the results of experimental and numerical investigation of propeller scale effects, undertaken in co-operation of the Hamburg Ship Model Basin (HSVA), Germany, and Ship Design and Research Centre (CTO SA), Poland. The objective of the investigation was to test the adequacy of the methods currently used to account for the propeller scale effect and to develop possible improvement of the methods. HSVA has conducted model experiments in the large cavitation tunnel together with panel method and CFD calculations. CTO SA has performed model experiments in the towing tank, together with lifting surface and CFD calculations. Both institutions have suggested different new approaches to the problem and different new procedures to account for the propeller scale effects. In the article the procedures are presented together with the description of the underlying experimental and theoretical research.

18

Flow analysis of hydraulic poppet control valve by means of computional fluid dynamics

80%

Łazowski J. , Krasucki J.

Journal of KONES

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2012

|

tom Vol. 19, No. 1

251-259

EN

The poppet control valve is one of the most widespread hydraulic components. The paper purpose is the evaluation of flow characteristics of poppet valve by means of a complete numerical analysis. The aim of this analysis is to evaluate the valve fluid dynamic performance, exploiting computational fluid dynamics (CFD) techniques, in order to give the reliable indications needed to define the valve design criteria and avoid expensive experimental tests. The numerical analysis was performed by using the commercial code of CFD, and the numerical results show the complete flow field inside the valve. Axisymmetric as well as three-dimensional valve model was considered and the simulation results also are verified with experimental results. The results have confirmed the good accuracy of the simplified CFD analysis based on 2D axisymmetric valve model being more efficient than full 3D approach and show this method as very useful to forecast flow characteristics of poppet control valves. Hydraulic control poppet valve, distribution of the velocity in layers of the fluid, computational grid in the modelled geometry, pressure distribution for axisymmetric and three-dimensional mode for different flow rate, fluid velocity distribution in valve metering section for axisymmetric and three-dimensional model for different flow rates, the example of streamlines, the comparison of flow characteristics are contained in the publication.

19

Computational modeling of centrifugal casting of alumina matrix composite reinforced with crystalline particles

80%

Zagórski R.

Computer Methods in Materials Science

|

2007

|

tom Vol. 7, No. 2

202-207

EN

The centrifugal casting of alumina matrix composite reinforced with crystalline particles (SiC) are studied. The influence of cast process parameters like pouring temperature, temperature, rotating speed and size of casting mould on structure of composite are examined. During centrifugal casting of alloys containing dispersed particles of crystalline, particles move under influence of centrifugal force and segregate. Numerical simulations are performed using the FLUENT two-phase free surface (air and matrix) unsteady flow model (volume of fluid model – VOF) and discrete phase model (DPM).

PL

Odlewanie odśrodkowe jest jedną z metod otrzymywania kompozytów aluminiowych zbrojonych cząsteczkami ceramicznymi. W trakcie procesu następuję segregacja cząsteczek zbrojenia pod wpływem działania siły odśrodkowej. Struktura kompozytu zależy również i od innych czynników: tj. różnicy gęstości pomiędzy materiałem osnowy i zbrojeniem, procesów termicznych związanych z krzepnięciem prowadzącym do zmiany we właściwościach fizycznych ciekłego kompozytu, temperatury zalewania, temperatury formy, składu i właściwości fizycznych kompozytu, prędkości wirowania, rozmiaru cząsteczek zbrojenia i innych. Ze względu na złożoność procesu, w którym wiele zjawisk ma charakter nieliniowy, matematyczny opis procesu jest zagadnieniem trudnym. Rozwój technik komputerowych spowodował, że modelowanie układów ciągłych, a za taki można uznać układ: ciekła osnowa kompozytu i zbrojenie, staje się możliwe, nawet w przypadku złożonego charakteru zagadnienia. W niniejszej pracy przedstawiono opis projektu, w którym podjęto próbę komputerowego modelowania procesu odlewania odśrodkowego kompozytów aluminiowych zbrojonych cząsteczkami ceramicznymi (SiC) od momentu zalewania formy do zastygnięcia kompozytu. W badanych wykorzystano program Fluent, który należy do grupy narzędzi tzw. numerycznej dynamiki płynów CFD (ang. computational fluid dynamie). Program Fluent podobnie jak szereg innych podobnych programów, opiera się na metodzie elementów skończonych oraz metodzie objętości skończonej. Zawiera szereg gotowych procedur, które zastosowano do zamodelowanie odlewania odśrodkowego kompozytów metalowych, tzn. procedury do obliczania rozkładu temperatur oraz prędkości dla dwuwymiarowego układu wirującego (ang. 2D axisymmetric swirl modę!), powierzchni swobodnej (ang. volume of fluid - VOF), cząsteczek stanowiących fazę rozproszoną (ang. discrete phase model - DPM). Ponadto umożliwia dodawanie własnych procedur, definiowanie dodatkowych parametrów i implementowanie ich w programie (User-Defined-Functions - UDFs), co było niezbędne w prezentowanym przypadku. W obliczeniach numerycznych uwzględniono wzajemne oddziaływania pomiędzy ciekłą osnową i zbrojeniem - wymiana ciepła i pędu. Ponadto, przyjęto, że na cząsteczkę zbrojenia oprócz siły odśrodkowej działają i inne siły, tj. grawitacja, wy-poru oraz oporu wynikająca z ruch cząsteczki w płynie o określonej lepkości. Zaniedbano natomiast oddziaływania między cząsteczkowe, traktując cząsteczki zbrojenia jako sztywne kule, które blokują zajmowaną przez siebie objętość. Uwzględniono zależność temperaturową takich parametrów ciekłej osnowy jak: gęstość, przewodnictwo cieplne oraz lepkość. Proces zastygania kompozytu zamodelowano poprzez zmianę lepkości ciekłej osnowy wraz ze zmianą temperatury.

20

Effects of different mesh schemes and turbulence models in cfd modelling of stirred tanks

80%

Karimi M. , Akdogan G. , Bradshaw S. M.

Physicochemical Problems of Mineral Processing

|

2012

|

tom Vol. 48, iss. 2

513-531

EN

This paper focuses on the effects of grid schemes and turbulence models on the CFD modelling of stirred tanks. The economical grid was determined by examining the dimensionless wall distance and the skewness of elements. The grid independency study ensured that the independency of numerical predictions. Also, three categories of turbulence models were compared for prediction of flow pattern. The grid sensitivity study highlighted that the quality of control volumes in the bulk and near the wall regions are significant for obtaining the consistent solutions. It was also found that for the prediction of velocity components and the turbulent quantity the RANS based models are more efficient.