Inhaltsverzeichnis
Auswahl der wissenschaftlichen Literatur zum Thema „SST k-ω turbulence model“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "SST k-ω turbulence model" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Zeitschriftenartikel zum Thema "SST k-ω turbulence model"
1
Shen, De Zhang, He Zhang und Hao Jie Li. „Comparison of Two Two-Equation Turbulence Model Used for the Numerical Simulation of Underwater Ammunition Fuze Turbine Flow Field“. Advanced Materials Research 591-593 (November 2012): 1968–72. http://dx.doi.org/10.4028/www.scientific.net/amr.591-593.1968.
Der volle Inhalt der QuelleAnnotation:
To figure out the problem of turbulence simulation of underwater ammunition fuze turbine numerical simulation, respectively, realizable k-ε turbulence model and SST k-ω turbulence model are used for two-phase flow numerical simulation of the turbine rotation. The analysis compared the calculation results of the two turbulence models. The results showed that: the cavitation scale obtained from realizable k-ε turbulence model is shorter than that of SST k-ω turbulence model; turbine surface pressure distribution trends are similar of this two model, the results of realizable k-ε turbulence model are bigger than SST k-ω turbulence model; the turbine axial pressure coefficients using realizable k-ε turbulence model are also bigger than that of SST k-ω turbulence model, and the deviation increases with the speed increase.
2
Genç, M. S. „Numerical Simulation of Flow over a Thin Aerofoil at a High Reynolds Number Using a Transition Model“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, Nr. 10 (12.02.2010): 2155–64. http://dx.doi.org/10.1243/09544062jmes2121.
Der volle Inhalt der QuelleAnnotation:
In this study, a prediction of the transition and stall characteristics of an NACA64A006 thin-aerofoil was numerically simulated by FLUENT using k— kL—ω and k—ω shear-stress transport (SST) transition models, recently developed, and k—ω SST and k—ε turbulence models. Subsonic flow with free stream Mach number ( M∞) of 0.17 and the high Reynolds number ( Re) of 5.8×106 was considered at an angle of attack varying from 2° to 11°. However, the computed results were compared with the experiments of McCollough and Gault. Lift and pressure curves were accurately predicted using the k— kL—ω transition model, while the k—ω SST transition model and the k—ω SST and k—ε turbulence models did not have a good agreement with the experimental results. The k— kL—ω transition model showed that the laminar separation and turbulent reattachment occurred near the leading edge of the NACA64A006 thin aerofoil, which caused the formation of the laminar separation bubble on the suction surface as in the experiments. Consequently, the transition and stalling characteristics of this aerofoil were successfully predicted using FLUENT with the k— kL—ω transition model at high Re number flow.
3
Teodosiu, Cătălin, Viorel Ilie und Raluca Teodosiu. „Appropriate CFD Turbulence Model for Improving Indoor Air Quality of Ventilated Spaces“. Mathematical Modelling in Civil Engineering 10, Nr. 4 (01.12.2014): 28–42. http://dx.doi.org/10.2478/mmce-2014-0020.
Der volle Inhalt der QuelleAnnotation:
Abstract Accurate assessment of air-flow in ventilated spaces is of major importance for achieving healthy and comfortable indoor environment conditions. The CFD (Computational Fluid Dynamics) technique is nowadays one of the most used approaches in order to improve the indoor air quality in ventilated environments. Nevertheless, CFD has still two main challenges: turbulence modeling and experimental validation. As a result, the objective of this study is to evaluate the performance of different turbulence models potentially appropriate for the prediction of indoor airflow. Accordingly, results obtained with 6 turbulence models (standard k-ε model, RNG k-ε model, realizable k-ε model, LRN SST k-ω model, transition SST k-ω model and low Reynolds Stress-ω model) are thoroughly validated based on detailed experimental data. The configuration taken into account in this work corresponds to isothermal and anisothermal airflows produced by mixing ventilation systems in small enclosures at low room air changes per hour. In general, the transition SST k-ω model shows the better overall behavior in comparison with measurement values. Consequently, the application of this turbulence model is appropriate for air flows in ventilated spaces, being an interesting option to more sophisticated LES (Large Eddy Simulation) models as it requires less computational resources.
4
Barnes, Andrew, Daniel Marshall-Cross und Ben Richard Hughes. „Validation and comparison of turbulence models for predicting wakes of vertical axis wind turbines“. Journal of Ocean Engineering and Marine Energy 7, Nr. 4 (23.07.2021): 339–62. http://dx.doi.org/10.1007/s40722-021-00204-z.
Der volle Inhalt der QuelleAnnotation:
AbstractVertical axis wind turbine (VAWT) array design requires adequate modelling of the turbine wakes to model the flow throughout the array and, therefore, the power output of turbines in the array. This paper investigates how accurately different turbulence models using 2D computational fluid dynamics (CFD) simulations can estimate near and far wakes of VAWTs to determine an approach towards accurate modelling for array design. Three experiments from the literature are chosen as baselines for validation, with these experiments representing the near to far wake of the turbine. Five URANS turbulence models were chosen due to their common and potential usage for VAWT CFD: models k–ω SST, k–ω SST LRN, k–ω SSTI, transition SST, and k–kl–ω. In addition, the lifting line-free vortex wake (LLFWV) model was tested as an alternative to CFD for the far turbine wake where it was appropriate for use. The results for turbulent kinetic energy and vorticity were compared for the first experiment, whilst streamwise and cross-stream velocity were used for the other two experiments. It was found that none of the turbulence models tested or LLFVW produced adequate estimations within the methodology tested, however, transition SST produced the closest estimations. Further adjustments to the methodology are required to improve accuracy due to their large impact on results including use of 3D CFD, adjustment of surface roughness, and inlet flow characteristics.
5
Boertz, Hendrik, Albert Baars, Janusz T. Cieśliński und Sławomir Smoleń. „Turbulence Model Evaluation for Numerical Modelling of Turbulent Flow and Heat Transfer of Nanofluids“. Applied Mechanics and Materials 831 (April 2016): 165–80. http://dx.doi.org/10.4028/www.scientific.net/amm.831.165.
Der volle Inhalt der QuelleAnnotation:
In this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (Reynolds number between 6000 and 12000) with constant heat flux boundary condition using nanofluids. The nanofluid is modelled with the single-phase approach and the simulation results are compared with experimental data. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid with particle volume concentrations ranging from 0% to 10%. A prior turbulence model evaluation of k-ε-, k-ω- and k-ω-SST-model revealed substantial deviations between the tested models and resulted in applying the k-ω-SST-model for the simulation. Nusselt number predictions for the nanofluid are in agreement with experimental results and a conventional single-phase correlation. The mean deviation is in the range of 5%. Friction factor values show a mean deviation of 1.5% to a conventional single-phase correlation, however, they differ considerably from the nanofluid experimental data.
6
Matyushenko, A. A., und A. V. Garbaruk. „Non-linear correction for the k-ω SST turbulence model“. Journal of Physics: Conference Series 929 (November 2017): 012102. http://dx.doi.org/10.1088/1742-6596/929/1/012102.
Der volle Inhalt der Quelle
7
Engdar, Ulf, Per Nilsson und Jens Klingmann. „Investigation of Turbulence Models Applied to Premixed Combustion Using a Level-Set Flamelet Library Approach“. Journal of Engineering for Gas Turbines and Power 126, Nr. 4 (01.10.2004): 701–7. http://dx.doi.org/10.1115/1.1771687.
Der volle Inhalt der QuelleAnnotation:
Most of the common modeling approaches to premixed combustion in engineering applications are either based on the assumption of infinitely fast chemistry or the flamelet assumption with simple chemistry. The level-set flamelet library approach (FLA) has shown great potential in predicting major species and heat release, as well as intermediate and minor species, where more simple models often fail. In this approach, the mean flame surface is tracked by a level-set equation. The flamelet libraries are generated by an external code, which employs a detailed chemical mechanism. However, a model for the turbulent flame speed is required, which, among other considerations, depends on the turbulence intensity, i.e., these models may show sensitivity to turbulence modeling. In this paper, the FLA model was implemented in the commercial CFD program Star-Cd, and applied to a lean premixed flame stabilized by a triangular prism (bluff body). The objective of this paper has been to investigate the impact on the mean flame position, and hence on the temperature and species distribution, using three different turbulent flame speed models in combination with four different turbulence models. The turbulence models investigated are: the standard k-ε model, a cubic nonlinear k-ε model, the standard k-ω model and the shear stress transport (SST) k-ω model. In general, the computed results agree well with experimental data for all computed cases, although the turbulence intensity is strongly underestimated at the downstream position. The use of the nonlinear k-ε model offers no advantage over the standard model, regardless of flame speed model. The k-ω based turbulence models predict the highest turbulence intensity with the shortest flame lengths as a consequence. The Mu¨ller flame speed model shows the least sensitivity to the choice of turbulence model.
8
Deng, Yilin, Jian Feng, Fulai Wan, Xi Shen und Bin Xu. „Evaluation of the Turbulence Model Influence on the Numerical Simulation of Cavitating Flow with Emphasis on Temperature Effect“. Processes 8, Nr. 8 (17.08.2020): 997. http://dx.doi.org/10.3390/pr8080997.
Der volle Inhalt der QuelleAnnotation:
The aim of this paper is to investigate the influence of different turbulence models (k−ε, RNG k−ε, and SST k−ω) on the numerical simulation of cavitating flow in thermosensitive fluid. The filter-based model and density correction method were employed to correct the turbulent viscosity of the three turbulence models. Numerical results obtained were compared to experimental ones which were conducted on the NACA0015 hydrofoil at different temperatures. The applicability of the numerical solutions of different turbulence model was studied in detail. The modified RNG k−ε model has higher accuracy in the calculation of cavitating flow at different temperatures.
9
Povilaitis, Mantas, und Justina Jaseliūnaitė. „Simulation of Hydrogen-Air-Diluents Mixture Combustion in an Acceleration Tube with FlameFoam Solver“. Energies 14, Nr. 17 (03.09.2021): 5504. http://dx.doi.org/10.3390/en14175504.
Der volle Inhalt der QuelleAnnotation:
During a severe accident in a nuclear power plant, hydrogen can be generated, leading to risks of possible deflagration and containment integrity failure. To manage severe accidents, great experimental, analytical, and benchmarking efforts are being made to understand combustible gas distribution, deflagration, and detonation processes. In one of the benchmarks—SARNET H2—flame acceleration due to obstacle-induced turbulence was investigated in the ENACCEF facility. The turbulent combustion problem is overly complex because it involves coupling between fluid dynamics, mass/heat transfer, and chemistry. There are still unknowns in understanding the mechanisms of turbulent flame propagation, therefore many methods in interpreting combustion and turbulent speed are present. Based on SARNET H2 benchmark results, a two-dimensional computational fluid dynamics simulation of turbulent hydrogen flame propagation in the ENACCEF facility was performed. Four combustible mixtures with different diluents concentrations were considered—13% H2 and 0%/10%/20%/30% of diluents in air. The aim of this numerical simulation was to validate the custom-built turbulent combustion OpenFOAM solver based on the progress variable model—flameFoam. Furthermore, another objective was to perform parametric analysis in relation to turbulent speed correlations and turbulence models and interpret the k-ω SST model blending function F1 behavior during the combustion process. The obtained results show that in the simulated case all three turbulent speed correlations behave similarly and can be used to reproduce observable flame speed; also, the k-ε model provides more accurate results than the k-ω SST turbulence model. It is shown in the paper that the k-ω SST model misinterprets the sudden parameter gradients resulting from turbulent combustion.
10
Amorim, Felipe Grossi L., Jean Helder M. Ribeiro, Marília Gabriela J. Vaz und Ramon Molina Valle. „Sensitivity Analysis of the Air Flow inside a Single Cylinder Engine for Different Turbulence Models Using CFD“. Advanced Materials Research 1016 (August 2014): 624–29. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.624.
Der volle Inhalt der QuelleAnnotation:
Theincrease of greenhouse gases emissions makes necessary to improve the comprehension of the Internal Combustion Engines operation. One of the factors that affect the combustion in these engines is the turbulence, since it can raise the quality of the fuel-air mixture inside the combustion chamber. However, when modeling internal combustion engines using CFD, the turbulence model choice is always a relevant problem. The present paper analyzes the results for three different turbulence models (k-ε Realizable, RNG k-ε and Menter k-ω SST) ina single-cylinder engine geometry, comparing numerical and experimental pressure data. For this experiment, the k-ε models obtained more trustable results than the k-ω SST, using less computational resources. The models achieved good results for eddy recirculation inside de cylinder and in regions of free shear flow at the valve openings, which makes possible to observe the correlation between parameters such as tumble and turbulent kinetic energy.
Dissertationen zum Thema "SST k-ω turbulence model"
1
Zhao, Yuer. „A Numerical Study of Melt Pool Heat Transfer in the IVR of a PWR“. Thesis, KTH, Fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297867.
Der volle Inhalt der QuelleAnnotation:
This thesis aims to provide the thermal condition of melt pool convection by CFD simulation, which is important to the assessment of the invessel melt retention (IVR) strategy widely adopted in Generation III pressurized water reactors (PWRs). As a severe accident mitigation measure, the IVR strategy is realized through external cooling of the lower head of a reactor pressure vessel (RPV). To achieve the coolability and retention of the corium pool in the RPV lower head, the heat flux at the outer surface of the vessel should be less than the critical heat flux (CHF) of boiling around the lower head. Under such condition, the integrity of the RPV is guaranteed by the adequate thickness of the unmelted vessel wall. The thesis work starts from the selection and validation of a turbulence model in the CFD computational tool chosen (Fluent). Afterwards a numerical model is set up for estimation of melt pool heat transfer of a reference PWR with the power capacity of 1000 MWe, including a mesh sensitivity study. Based on the numerical model of a twolayer melt pool, four tasks are carried out to investigate the effects of Zr oxidation ratio, Fe content, and radiation emissivity on heat flux profiles, as well as the focus effect under extreme conditions. Selection and validation of the turbulence model are conducted by comparing the simulation results of different turbulence models with the DNS data on the convection of volumetrically heated fluid layer bounded by rigid isothermal horizontal walls at equal temperature. The internal Rayleigh numbers of the flow reach up to 10e6. The comparison shows a good agreement of the SST k-ω turbulence model results with the DNS data. The simulations with the Zr oxidation ratio of 0, 0.2 and 0.5, correspondingly, the oxide layer of 1.389m, 1.467m and 1.580m, and the metal layer of 0.705m, 0.646m and 0.561m in height, show that, the temperature of the oxide layer will increase with Zr oxidation ratio, while the temperature of the metal layer will decrease resulting in more heat transfer through the oxide layer sidewall and less top radiation. Nevertheless, the effect of the Zr oxidation ratio is not pronounced in the range of 00.5. The simulations with the Fe mass of 22t, 33t and 45t, and respective height of the metal layer of 0.462m, 0.568m and 0.646m, show that, the inner metal layer will significantly increase the temperatures of both the metal layer and the oxide layer. The percentage of heat transfer at the oxide layer sidewall will increase to supplement the reduction of that at the metal layer. The simulations with the radiation emissivity of 0.2, 0.35, 0.45 and 0.7 show that, the emissivity below 0.45 has an impact on heat transfer, and the temperatures and sidewall heat flux of both the oxide layer and the metal layer will increase with decreasing emissivity. The impact is negligible when the emissivity is above 0.45. The simulations under the hypothetically extreme conditions with either an adiabatic top boundary or a very thin metal layer show the focusing effect may occur, i.e., the heat flux through the metal sidewall is larger than that in the oxide layer. But the local high heat flux is flattened by the vessel wall with good heat conductivity. In summary, the simulations demonstrate that, except for the cases under extreme conditions, the heat fluxes of the melt pools in all other cases are significantly lower than the CHF of external cooling of the lower head. Therefore, the safety margin of the IVR strategy of the PWR chosen is seems sufficient. However, due to some limitations (e.g., simplification and assumptions) in the simulation cases and coupling of different influential factors, as indicated by the present study, the precise predictions of heat flux under all scenarios are still difficult. Therefore, the conclusions could not be generalized to the other conditions or other configurations of the molten pools. By discussing the model and simplifications/assumptions adopted in this work, the improvement directions of the numerical model and other perspectives are proposed at the end of the thesis.Denna avhandling syftar till att tillhandahålla det termiska tillståndet för smältbassängskonvektion genom CFD-simulering, vilket är viktigt för bedömningen av IVR-strategin som allmänt antagits i tryckvattenreaktorer (PWR) i Generation III. Som en åtgärd för att mildra allvarliga olyckor realiseras IVR-strategin genom extern kylning av det nedre huvudet av ett reaktortryckkärl (RPV). För att uppnå kylbarhet och kvarhållning av koriumbassängen i det nedre RPV-huvudet bör värmeflöde vid den yttre ytan av kärlet vara mindre än det kritiska värmeflödet (CHF) som kokar runt det nedre huvudet. Under sådant tillstånd garanteras RPV: s integritet av den osmälta kärlväggens tillräckliga tjocklek. Examensarbetet startar från valet och valideringen av en turbulensmodell i det valda CFD-beräkningsverktyget (Fluent). Därefter sätts en numerisk modell upp för uppskattning av smältbassängens värmeöverföring av en referens PWR med en effektkapacitet på 1000 MWe, inklusive en nätkänslighetsstudie. Baserat på den numeriska modellen för en tvålagers smältbassäng utförs fyra uppgifter för att undersöka effekterna av Zr-oxidationsförhållande, Fe-innehåll och strålningsemissivitet på värmeflödesprofiler, liksom fokuseffekten under extrema förhållanden. Val och validering av turbulensmodellen utförs genom att jämföra simuleringsresultaten för olika turbulensmodeller med DNS-data för konvektionen av volymetriskt uppvärmt fluidskikt avgränsat av styva isoterma horisontella väggar vid lika temperatur. De interna Rayleigh-siffrorna i flödet når upp till 10e6. Jämförelsen visar att SST k-ω turbulensmodellresultaten överensstämmer med DNS-data. Simuleringarna med Zr-oxidationsförhållandet 0, 0,2 och 0,5, motsvarande oxidskiktet på 1,389 m, 1,467 m och 1,580 m, och metallskiktet på 0,705 m, 0,664 m och 0,561 m i höjd, visar att temperaturen av oxidskiktet kommer att öka med Zr-oxidationsförhållandet, medan metallskiktets temperatur kommer att minska vilket resulterar i mer värmeöverföring genom oxidskiktets sidovägg och mindre toppstrålning. Ändå är effekten av Zr-oxidationsförhållandet inte uttalad i intervallet 00,5. Simuleringarna med Fe-massan på 22t, 33t och 45t och respektive höjd av metallskiktet på 0,462m, 0,568m och 0,664m visar att det inre metallskiktet avsevärt kommer att öka temperaturerna för både metallskiktet och oxiden lager. Andelen värmeöverföring vid oxidskiktets sidovägg ökar för att komplettera minskningen av den vid metallskiktet. Simuleringarna med strålningsemissiviteten 0,2, 0,35, 0,45 och 0,7 visar att emissiviteten under 0,45 påverkar värmeöverföringen, och temperaturerna och sidoväggens värmeflöde för både oxidskiktet och metallskiktet kommer att öka med minskande emissivitet. Effekten är försumbar när strålningen är över 0,45. Simuleringarna under de hypotetiskt extrema förhållandena med antingen en adiabatisk övre gräns eller ett mycket tunt metallskikt visar att fokuseringseffekten kan uppstå, dvs. värmeflödet genom metallsidan är större än det i oxidskiktet. Men det lokala höga värmeflödet plattas ut av kärlväggen med god värmeledningsförmåga. Sammanfattningsvis visar simuleringarna att, förutom fall under extrema förhållanden, är värmeflödet från smältpoolerna i alla andra fall betydligt lägre än CHF för extern kylning av nedre huvudet. Därför verkar säkerhetsmarginalen för IVR-strategin för den valda PWR tillräcklig. På grund av vissa begränsningar (t.ex. förenkling och antaganden) i simuleringsfall och koppling av olika inflytelserika faktorer, vilket indikeras av den aktuella studien, är de exakta förutsägelserna av värmeflöde under alla scenarier fortfarande svåra. Därför kunde slutsatserna inte generaliseras till de andra förhållandena eller andra konfigurationer av de smälta poolerna. Genom att diskutera modellen och förenklingar / antaganden som antagits i detta arbete föreslås förbättringsriktningarna för den numeriska modellen och andra perspektiv i slutet av avhandlingen.
2
Yilmaz, Ali Emre. „Implementation Of Turbulence Models On 2d Hybrid Grids Using An Explicit/implicit Multigrid Algorithm“. Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613783/index.pdf.
Der volle Inhalt der QuelleAnnotation:
In this thesis study, implementation, numerical stability and convergence rate issues of turbulence modeling are explored. For this purpose, a one equation turbulence model, Spalart-Allmaras, and a two-equation turbulence model, SST k-w, are adapted to an explicit, cell centered, finite volume method based, structured / hybrid multi grid flow solver, SENSE2D, developed at TUBITAK-SAGE. Governing equations for both the flow and the turbulence are solved in a loosely coupled manner, however, each set of equations are solved using a coupled, semi-implicit solution algorithm. In multigrid solutions, the semi-implicit solution algorithm and the turbulence model equations are employed only in the finest level grid. As a result, stable and convergent numerical solutions are obtained. In order to validate the turbulence models and the semi-implicit solution algorithm implemented, turbulent flow solutions over a flat plate, RAE2822 airfoil and NLR7301 multi element airfoil are performed. The results are compared with the experimental data and the numerical results of the commercial CFD package FLUENT. It is shown that the numerical results obtained by SENSE2D are in good agreement with the experimental data and the FLUENT results. In addition to the turbulence modeling studies, convergence rate studies are also performed by multigrid and semi-implicit solution methods. It is shown that, the convergence
rates of the semi-implicit solutions are increased about 5 times for single grid and 35% for multigrid solutions in comparison to the explicit solutions.
3
Fernandes, Marcos Paulo Gomes. „CalibraÃÃo do Modelo de TurbulÃncia k-ω SST para Turbinas EÃlicas de Pequeno Porte AtravÃs de AvaliaÃÃo NumÃrica e Experimental“. Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9378.
Der volle Inhalt der QuelleAnnotation:
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorNo presente trabalho foi realizada a investigaÃÃo numÃrica e experimental do desempenho aerodinÃmico de dois aerogeradores tripà de pequeno porte com 3 m de diÃmetro. Os perfis aerodinÃmicos utilizados, NACA 0012 (simÃtrico) e NACA 4412 (cambado), foram projetados para aplicaÃÃes em baixas velocidades, como à o caso de turbinas eÃlicas de eixo horizontal. Os aerogeradores foram construÃdos e testados no LaboratÃrio de Energia Solar e GÃs Natural - UFC. Isto permitiu a determinaÃÃo das curvas de desempenho dos mesmos, possibilitando a comparaÃÃo posterior com os resultados da anÃlise numÃrica. A fim de calibrar o modelo de turbulÃncia k-ω SST para aplicaÃÃo em turbinas eÃlicas de pequeno porte, foram realizadas simulaÃÃes numÃricas utilizando o pacote de CFD OpenFOAM, versÃo 1.7.1. Os resultados numÃricos e experimentais foram comparados, de tal forma que, a partir da variaÃÃo de parÃmetros como intensidade de turbulÃncia, comprimento caracterÃstico turbulento e β* (constante de calibraÃÃo do modelo), pode-se concluir que os resultados numÃricos foram pouco sensÃveis aos dois primeiros parÃmetros, enquanto a variaÃÃo de β* impactou de forma significativa os resultados numÃricos. A mudanÃa do aerofÃlio nÃo alterou o valor de β* que melhor ajustou o resultado. Isto, alÃm do sucesso do processo de calibraÃÃo, indica que a cambagem nÃo influenciou na calibraÃÃo do modelo de turbulÃncia, o que à muito positivo, pois permite uma avaliaÃÃo de cenÃrios diferentes, tal como pÃs projetadas com outros perfis aerodinÃmicos.
In this work it was performed a numerical and experimental investigation of the aerodynamic performance of two small three-bladed wind turbines with diameter of 3m. The airfoils used, NACA 0012 (symmetrical) e NACA 4412 (unsymmetrical), were designed for low speed applications, such as the horizontal axis wind turbines. The wind turbines were built and tested at the Solar Energy and Natural Gas Laboratory âUFC. This allowed the attainment of the performance curves, enabling the comparison between the results of the numerical analysis. In order to calibrate the turbulence model k-ω SST to applications in small wind turbines, it was performed numerical simulations using the open source package for CFD solutions OpenFOAM, version 1.7.1. The numerical and experimental results were compared, in a way that, from the variation of parameters such as turbulence intensity, characteristic length and β* (calibration constant), it can be concluded that the numerical results were little sensitive to the first two parameters, while the variation of β* impacted significantly the numerical results. The change of airfoil did not modify the value of β* that best adjusted the result. This, beyond the success of the calibration process, indicates that the camber did not affect the calibration of the turbulence model, which is very positive because it allows an evaluation of different scenarios, such as blades designed with other airfoils.
4
Andersson, Harald. „Numerical and experimental study of confluent jets supply device with variable airflow“. Licentiate thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-29271.
Der volle Inhalt der QuelleAnnotation:
In recent years, application of confluent jets for design of ventilation supply devices has been studied. Similarly, numerus studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of supply devices based on confluent jets and VAV, both in terms of the nearfield flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency on a classroom-level space when the airflow rate is varied. The method used in this study is an experimental field study where the confluent jets-based supply devices were compared to the previously installed displacement ventilation. The field study evaluated the energy efficiency, thermal comfort and indoor air quality of the two systems. In the case of the confluent jets supply devices, airflow rate was varied in order to see what impact the variation had on the performance of the system for each airflow rate. Furthermore, the confluent jets supply devices were investigated both experimentally and numerically in a well insulated test room to get high resolution data on the particular flow characteristics for this type of supply device when the airflow rate is varied. The results from the field study show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low airflow rates. The airflow rates have no significant effect on the degree of mixing. The thermal comfort in the classroom was increased when the airflow rate was adapted to the heat load compared to the displacement system. The results lead to the conclusion that the combination of supply devices based on confluent jets can reduce energy usage in the school while maintaining indoor air quality and increasing the thermal comfort in the occupied zone. The results from the experimental and numerical study show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for different airflow rates. The results from both studies show that the airflow rate does not affect the distribution of the airflow on both near-field and room level. The distribution of air is nearly uniform in the case of the near-field results and the room-level measurement shows a completely uniform degree of mixing and air quality in the occupied zone for each airflow rate. This means that there is potential for combining these two schemes for designing air distribution systems with high energy efficiency and high thermal comfort and indoor air quality.Under senare tid har applikation av Confluent jets för design av tilluftsdon studerats. Många studier har även utförts över potentialen av att applicera variabelt luftflöde (VAV) för att minska energianvändningen i ventilationssystem. Denna studie undersöker möjligheten att kombinera Confluent jets-don med VAV, både med avseende på den lokala flödesbilden och dess påverkan på termisk komfort, luftkvalitet och energieffektivitet i en klassrumsmiljö där luftflödes varieras. Denna studie baseras dels på en experimentell fältstudie där tilluftsdon baserade på Confluents jets jämfördes med befintliga deplacerande tilluftsdon. Fältstudien utvärderade energieffektiviteten, den termiska komforten och luftkvaliteten för båda typerna av tillluftsdon. Confluent jets-donen testades under varierat luftflöde för att se påverkan av flödesvariationen på ventilationens prestation under de olika flödena. Utöver fältstudien testades Confluent jets-donen experimentellt och numeriskt i ett välisolerat test-rum för få den detaljerade flödeskarakteristiken för den här typen tilluftsdon vid varierat luftflöde. Resultaten från fältstudien visar på en jämn fördelning av den lokala luftsmedelåldern i vistelsezonen, även för fallen med relativt låga luftflöden. Luftflöden har ingen signifikant effekt på omblandningen. Den termiska komforten i klassrummet ökade när luftflödet anpassades efter värmelasten jämfört med de deplacerande donen. Slutsatsen från fältstudien är att kombinationen av VAV och Confluent jets-don kan användas för att minska energianvändningen på skolan och bevara luftkvaliteten och den termiska komforten i vistelsezonen. Resultaten från den experimental och numeriska studien visar luftflödet och lufthastigheten i varje enskild dysa är direkt beroende på det totala luftflödet genom donet. Dock är flödesfördelningen mellan dysorna oberoende av de tre olika luftflödena. Den numeriska undersökningen visar att flödesprofilen för varje dysa är konstant trots att flödet varieras, men amplituden för varje profil ökar med en höjning av luftflödet. Det betyder att tilluftsdon av den här typen kan användas med VAV för att producera Confluent jets för olika luftflöden. Resultaten från båda studierna visar att luftflöde inte påverkar fördelningen av luften vare sig längs luftdonen eller på rumsnivå. Fördelningen av luften är nästan helt jämn längs donen och på rumsnivå är omblandningen och luftkvalitet den samma för varje luftflöde. Det betyder att det finns potential för att kombinera det här två teknikerna för att designa luftdistribueringssystem med hög energieffektivitet och hög termisk komfort med god luftkvalitet.
5
Janbakhsh, Setareh. „A Ventilation Strategy Based on Confluent Jets : An Experimental and Numerical Study“. Doctoral thesis, Linköpings universitet, Energisystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-117442.
Der volle Inhalt der QuelleAnnotation:
This study presents air distribution systems that are based on confluent jets; this system can be of interest for the establishment of indoor environments, to fulfill the goals of indoor climate and energy-efficient usage. The main objective of this study is to provide deeper understanding of the flow field development of a supply device that is designed based on wall confluent jets and to investigate the ventilation performance by experimental and numerical methods. In this study, the supply device can be described as an array of round jets on a flat surface attached to a side wall. Multiple round jets that issue from supply device apertures are combined at a certain distance downstream from the device and behave as a united jet or so-called confluent jets. Multiple round jets that are generated from the supply device move downward and are attached to the wall at the primary region, due to the Coanda effect, and then they become wall confluent jets until the floor wall is reached. A wall jet in a secondary region is formed along the floor after the stagnation region. The characteristics of the flow field and the ventilation performance of conventional wall confluent jets and modified wall confluent jets supply devices are investigated experimentally in an office test room. The study of the modified wall confluent jets is intended to improve the efficiency of the conventional one while maintaining acceptable thermal comfort in an office environment. The results show that the modified wall confluent jets supply device can provide acceptable thermal comfort for the occupant with lower airflow rate compared to the conventional wall confluent jets supply device. Numerical predictions using three turbulence models (renormalization group (RNG k– ε), realizable (Re k– ε), and shear stress transport (SST k– ω) are evaluated by measurement results. The computational box and nozzle plate models are used to model the inlet boundary conditions of the nozzle device. In the isothermal study, the wall confluent jets in the primary region and the wall jet in the secondary region, when predicted by the three turbulence models, are in good agreement with the measurements. The non-isothermal validation studies show that the SST k– ω model is slightly better at predicting the wall confluent jets than the other two models. The SST k– ω model is used to investigate the effects of the nozzle diameter, number of nozzles, nozzle array configuration, and inlet discharge height on the ventilation performance of the proposed wall confluent jets supply device. The nozzle diameter and number of nozzles play important roles in determining the airflow pattern, temperature field, and draught distribution. Increased temperature stratification and less draught distribution are achieved by increasing the nozzle diameter and number of nozzles. The supply device with smaller nozzle diameters and fewer nozzles yields rather uniform temperature distribution due to the dominant effect of mixing. The flow behavior is nearly independent of the inlet discharge height for the studied range. The proposed wall confluent jets supply device is compared with a mixing supply device, impinging supply device and displacement supply device. The results show that the proposed wall confluent jets supply device has the combined behavior of both mixing and stratification principles. The proposed wall confluent jets supply device provides better overall ventilation performance than the mixing and displacement supply devices used in this study. This study covers also another application of confluent jets that is based on impinging technology. The supply device under consideration has an array of round jets on a curve. Multiple jets issue from the supply device aperture, in which the supply device is positioned vertically and the jets are directed against a target wall. The flow behavior and ventilation performance of the impinging confluent jets supply device is studied experimentally in an industrial premise. The results show that the impinging confluent jets supply device maintains acceptable thermal comfort in the occupied zone by creating well-distributed airflow during cold and hot seasons.
6
Guillou, Florian. „CFD Study of the Flow around a High-Speed Train“. Thesis, KTH, Aerodynamik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102033.
Der volle Inhalt der QuelleAnnotation:
This document is a report summering the master thesis work dealing with the Computational Fluid Dynamic (CFD) study of the flow around a high-speed train. The model is a scaled 1:50 generic train with two cars, one inter-car gap and simplified bogies. A platform is set on the side of the train since one of the aim of the study is to look at the consequences of the phenomena in the wake on people or objects standing on the platform. The slipstream is one of this phenomena, it is due to the fact that the viscous air is dragged when the train is passing. If too strong, it can move or destabilize people or objects on the platform. In addition of the slipstream study, a velocity profile study, a drag and lift coefficients analyze as well as a Q-factor study and a frequency study have been realized. Some results of these different studies are compared with the ones obtained on the same model with a Delayed Detached Eddy Simulation (DDES). Since the flow is turbulent, for those different studies, the flow has been simulated with a Reynolds Averaged Navier-Stokes equation model (RANS) which is the k-ω SST model for the turbulence. The study of the slipstream allowed to calculate the Technical Specification for Interoperability (TSI) which must not be higher that the European Union requirement set at 15.5 m/s, the result obtained is 8.1 m/s which is then lower than the limit. The velocity profile shows similarities with the DDES results even though it is less detailed. The same conclusion is done for the Q-plot where is clearly visible the two counter-rotating vortices in the wake. Finally, a Fast Fourier Transform algorithm has been applied to instantaneous velocity results in the wake of the train in order to get the frequency of the aerodynamic phenomena in that wake. The main frequency is 25 Hz and corresponds to a Strouhal number of 0.1, quite closed to the results obtained with DDES which is 0.085. The results of the RANS and DDES are reasonably similar and by regarding at the large difference between the cell numbers (respectively 8 500 000 and 20 000 000) it can be conclude that in some ways the RANS model can be preferred at the DDES to save time for the computation but it does not contain the small scales resolved by the DDES.
7
Zhang, Zhi. „A study of flow fields during filling of a sampler“. Licentiate thesis, KTH, Materials Science and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10693.
Der volle Inhalt der QuelleAnnotation:
More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized.
The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.
Buchteile zum Thema "SST k-ω turbulence model"
1
Könözsy, László. „The k- $$\omega $$ ω Shear-Stress Transport (SST) Turbulence Model“. In A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 57–66. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_3.
Der volle Inhalt der Quelle
2
Ngouani, M. M. Siewe, Yong Kang Chen, R. Day und O. David-West. „Low-Speed Aerodynamic Analysis Using Four Different Turbulent Models of Solver of a Wind Turbine Shroud“. In Springer Proceedings in Energy, 149–54. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63916-7_19.
Der volle Inhalt der QuelleAnnotation:
AbstractThis study presents the effect of four different turbulent models of solver on the aerodynamic analysis of a shroud at wind speed below 6 m/s. The converting shroud uses a combination of a cylindrical case and an inverted circular wing base which captures the wind from a 360° direction. The CFD models used are: the SST (Menter) k-ω model, the Reynolds Stress Transport (RST) model, the Improved Delay Detached Eddies Simulation model (IDDES) SST k-ω model and the Large Eddies Simulation Wall Adaptive model. It was found that all models have predicted a convergent surface pressure. The RST, the IDDES and the WALE LES are the only models which have well described regions of pressure gradient. They have all predicted a pressure difference between the planes (1–5) which shows a movement of the air from the lower plane 1 (inlet) to the higher plane 5 (outlet). The RST and IDDES have predicted better vorticities on the plane 1 (inlet). It was also found that the model RST, IDDES, and WALE LES have captured properly the area of turbulences across the internal region of the case. All models have predicted the point of flow separation. They have also revealed that the IDDES and the WALE LES can capture and model the wake eddies at different planes. Thus, they are the most appropriate for such simulation although demanding in computational power. The movement of air predicted by almost all models could be used to drive a turbine.
3
Könözsy, László. „The Anisotropic Hybrid k-$$\omega $$ SST/Stochastic Turbulence Model“. In A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 115–40. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_2.
Der volle Inhalt der Quelle
4
El-Hennawi, Ahmed, Muhammed Eltahan, Mohammed Magooda und Karim Moharm. „Numerical Study of an Unbalanced Oil Vane Pump Using Shear Stress Transport (SST) k − ω Turbulence Model“. In Recent Advances in Engineering Mathematics and Physics, 87–98. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-39847-7_7.
Der volle Inhalt der Quelle
5
Menter, Florian R., Alexey Matyushenko und Richard Lechner. „Development of a Generalized K-ω Two-Equation Turbulence Model“. In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 101–9. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-25253-3_10.
Der volle Inhalt der Quelle
6
Radmanesh, Amir Reza, Madjid Abbaspour und Mohamad Reza Soltani. „Unsteady Aerodynamic Analysis of Different Multi-MW Horizontal Axis Wind Turbine Blade Profiles on SST K-ω Model“. In Exergy for A Better Environment and Improved Sustainability 1, 17–30. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-62572-0_2.
Der volle Inhalt der Quelle
7
Könözsy, László. „Implementation of the Anisotropic Hybrid k-$$\omega$$ SST/STM Closure Model“. In A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 141–214. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60603-9_3.
Der volle Inhalt der Quelle
8
Alkan, Ahmet Dursun, Onur Usta, Alpay Acar und Elis Atasayan. „Investigation of Environmental Effects of High Speed Boats“. In Progress in Marine Science and Technology. IOS Press, 2020. http://dx.doi.org/10.3233/pmst200021.
Der volle Inhalt der QuelleAnnotation:
Luxury high-speed boats are increasingly being used for entertainment purposes. However, not only humans, but also animals are negatively affected by high-speed boats, and time is running out fast for people to do something about it. This study presents a review of current negative effects of high-speed boats to the environment. In this study, the flow around a benchmark planing Fridsma boat is simulated by CFD and resistance values for different non-dimensional Froude number (Fn) conditions are validated from the experimental results obtained from the literature. Using the same CFD methodology, a catamaran model in which the towing tank test results are available, is simulated for different Fn conditions and resistance values are predicted. In the CFD analysis, unsteady flow around the Fridsma hull model and catamaran model is simulated using overset meshing technique and turbulence is modeled by Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-omega turbulence model. Resistance values are compared with the experimental data and required propulsion powers are estimated for different Fn conditions. Then, total resistance of the catamaran for full-scale vessel is calculated using an extrapolation method and required propulsion power predictions are conducted. Noise prediction, corresponding to the required propulsion power are presented. In particular, the change of noise level and harmful gases released into the environment, when the speed of the vessel increases are examined and discussed. Consequently, it is believed that this study would lay an important foundation for the widespread investigation for the negative effects of the high-speed boats in the future.
9
Kątski, Bartosz, und Krzysztof Rogowski. „Analiza własności aerodynamicznych profilu NACA 0018 w zakresie małych liczb Reynoldsa“. In Mechanika w Lotnictwie ML-XIX 2020, 57–65. Instytut Techniczny Wojsk Lotniczych, Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej, 2020. http://dx.doi.org/10.15632/ml2020/57-65.
Der volle Inhalt der QuelleAnnotation:
W pracy przedstawiono rezultaty badań numerycznych profilu aerodynamicznego NACA 0018 w zakresie małych liczb Reynoldsa od 10 000 do 1mln oraz w zakresie kątów natarcia od 0◦ do 20◦. Wyniki zaprezentowano w postaci charakterystyk współczynników siły nośnej i oporu w funkcji kąta natarcia. Badania przeprowadzono, wykorzystując model turbulencji k-! SST oraz hybrydową siatkę obliczeniową złożoną z siatki strukturalnej w pobliżu krawędzi profilu oraz siatkę niestrukturalną w pozostałym obszarze domeny obliczeniowej. Intencją autorów pracy było pokazanie możliwości zastosowania podejścia numerycznego w badaniach profili w zakresie małych liczb Reynoldsa. Przeprowadzone badania pokazały, że minimalna liczba Reynoldsa, przy której wartość błędu jest akceptowalna, wynosi 40 000. Rezultaty badań symulacyjnych sił aerodynamicznych przedstawiono również tabelarycznie do wykorzystania w innych analizach.
Konferenzberichte zum Thema "SST k-ω turbulence model"
1
Evans, Steve, und Sylvain Lardeau. „Validation of a turbulence methodology using the SST k-ω model for adjoint calculation“. In 54th AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-0585.
Der volle Inhalt der Quelle
2
Mehdizadeh, A., G. Vijayakumar, H. Foroutan und Amsini Sadiki. „A grid based zonal formulation of k-ω-SST-SAS model for complex turbulent flows“. In THMT-15. Proceedings of the Eighth International Symposium On Turbulence Heat and Mass Transfer. Connecticut: Begellhouse, 2015. http://dx.doi.org/10.1615/ichmt.2015.thmt-15.590.
Der volle Inhalt der Quelle
3
Chougule, Nagesh K., Gajanan V. Parishwad, Sachin Pagnis, Prashant R. Gore und Chandrashekhar M. Sewatkar. „Selection of CFD Turbulence Model for the Application of Submerged Multi-Air Jet Impingement“. In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64765.
Der volle Inhalt der QuelleAnnotation:
Most impinging jet industrial applications involve turbulent flow in the whole domain downstream of the nozzle, and modeling turbulent flow presents the greatest challenge in the effort to rapidly and accurately predict the behavior of turbulent jets. Numerical modeling of impinging jet flows and heat transfer is employed widely for prediction, sensitivity analysis, and device design. Finite volume computational fluid dynamics (CFD) models of impinging jets have succeeded in making good predictions of heat transfer coefficients and velocity fields. The difficulties in accurately predicting velocities and transfer coefficients stem primarily from modeling of turbulence and the interaction of the turbulent flow field with the wall. In present work, the flow and heat transfer characteristics of circular multi jet array (3×3) of 5mm diameter impinging on the Flat plate heat sink are numerically analyzed based on the CFD commercial code ANSYS CFX. The relative performance of four different turbulence models, including Standard k-ε, RNG k-ε, (Renormalization Group), Standard k-ω and SST (Shear-Stress Transport) k-ω models are done for the prediction of this type of flow and heat transfer is investigated by comparing the numerical results with experimental data. It is found that SST k-ω model gives better predictions with moderate computational cost. Using SST k-ω model, the effect of Reynolds number (Re) on the average Nusselt number (Nua) of target plate is examined at Z/d = 6 (Z/d is the gap between nozzle exit and target surface).
4
Zhou, Ling, Tao Lang und Weidong Shi. „Numerical Simulation of Different Turbulence Models in a Compact Return Diffuser“. In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-9574.
Der volle Inhalt der QuelleAnnotation:
CFD have been became the main method to study the pump inner flow patterns. It is important to understand the differences and features of the different turbulence models. In this paper, the velocity flow fields in a compact return diffuser under multi-conditions are studied by CFD and PIV measurements. In the numerical simulation, three turbulence models are used to solve the steady flow filed using high-quality fine structured grids, which are including SST k-ω model, DES model and SST k-ω model with low-Re corrections. A special test rig is designed to carry out the 2D Particle Image Velocimetry (PIV) measurements, and the PIV results are used to validate the CFD results. The detailed comparison between different turbulence models and PIV results is performed. Velocity flow fields in the diffuser middle section are compared and analyzed under different flow rates. SST k-ω model with low-Re correction give a better results comparing to DES and SST k-ω model, especially have a good predication about the vortex core position under strong part-loading conditions.
5
Lodefier, Koen, Bart Merci, Chris De Langhe und Erik Dick. „Transition Modelling With the SST Turbulence Model and an Intermittency Transport Equation“. In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38282.
Der volle Inhalt der QuelleAnnotation:
A transition model for describing bypass transition is presented. It is based on a two-equations k–ω model and a dynamic equation for intermittency factor. The intermittency factor is a multiplier of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al. [1], the start of transition is computed based on local variables. The choice of the Shear-Stress Transport (SST) model instead of a k–ε model is explained. The quality of the transition model, developed on flat plate test cases, is illustrated for cascades.
6
Wang, Yong, Houlin Liu, Shouqi Yuan, Minggao Tan und Minhua Shu. „Applicability of Turbulence Models on Characteristics Prediction of Centrifugal Pumps“. In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-03022.
Der volle Inhalt der QuelleAnnotation:
In order to research the applicability of turbulence model on characteristics prediction of centrifugal pumps at the design condition, standard k-ε turbulence model, k-ω turbulence model and SST turbulence model are selected, which are commonly used in the numerical prediction for head, efficiency and NPSHr of the centrifugal pumps. By using commercial code ANSYS CFX, the all three turbulent models are used to predict the characteristics of six centrifugal pumps with the different specific speeds at the design condition, which are varied from 34.3 to 260.5. The calculation results are compared with the experimental data, and the comparison indicates that all the prediction results obtained from different turbulence models are more or less different from the experimental data. The head and efficiency predicted by SST turbulence model and k-ω turbulence model are closer and they are all bigger than that predicted by k-ε turbulence model. For low specific speed centrifugal pumps, the head and efficiency predicted by SST model and the NPSHr predicted by k-ε turbulence model are more closer to the experimental values; while for the medium and high specific speed centrifugal pumps, the head and efficiency predicted by k-ε turbulence model are better than that predicted by other models. The k-ω turbulence model and k-ε turbulence model are the best choice to predict NPSHr of medium and high specific speed centrifugal pumps respectively.
7
Patel, Yogini, Teemu Turunen-Saaresti, Giteshkumar Patel und Aki Grönman. „Numerical Investigation of Turbulence Modelling on Condensing Steam Flows in Turbine Cascade“. In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26307.
Der volle Inhalt der QuelleAnnotation:
Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the turbulence modelling on the non-equilibrium homogeneous condensing steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-ε, the RNG k-ε, the Realizable k-ε, and the SST k-ω) in condensing steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of turbulence modeling in wet-steam flows.
8
Kumar Lakshmanan, Saravana, Alok Mishra und Ashoke De. „Assessment of Different Turbulence Models for Predicting Laminar Separation Bubble Over Thick Airfoils“. In ASME 2015 Gas Turbine India Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gtindia2015-1277.
Der volle Inhalt der QuelleAnnotation:
Accurate laminar-turbulent prediction is very much important to understand the complete performance characteristics of any airfoil which operates at low and medium Reynolds number. In this article, a numerical study has been performed over two different thick airfoils operating at low Reynolds number using k-ω SST, k-kl-ω and Spalart-Allmaras (SA) RANS models. The unsteady two dimensional (2D) simulations are performed over NACA 0021 and NACA 65-021 at Re 120,000 for a range of angle of attacks. The performances of these models are assessed through aerodynamic lift, drag and pressure coefficients. To obtain better comparison, the simulated results are compared with the experimental measurements and XFOIL results as well. In this present study, it is found that the k-kl-ω transition model is capable of predicting correct lift, drag coefficient and separation bubble as reported in experiments. At high angles of attack, this model fails to predict performance variables accurately. The SA and SST models are fail to predict laminar separation bubble. However, At high angle of attack, SA model shows better predictions compared to k-kl-ω and k-ω SST models.
9
Zhang, Li, Weimin Chen, Jianting Chen und Chuanming Zhou. „Verification and Validation of CFD Uncertainty Analysis Based on SST K-ω Model“. In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-19093.
Der volle Inhalt der QuelleAnnotation:
Abstract CFD uncertainty analysis is a process to quantify the accuracy of numerical simulation results, and it is also a research hotspot in the past decades. ITTC(2017) requires uncertainty analysis of ship CFD simulation results, that is, verification and validation. In this paper, with reference to the recommended procedures by ITTC, the uncertainty of the CFD numerical simulation results of ship model resistance was analyzed. Based on the SST k-ω turbulence model, the Y+ values near the wall were set to 60,120,240, respectively. And for each and Y+ value, three different sets of grid densities were set respectively, and the uncertainty was analyzed. The results show that: 1) the results of Y+ at 60 and 120 were not validated, and the results at 240 was validated, 2) the selection of Y+ value has a significant effect on the numerical results, 3) increasing the mesh density can make the result converge, but it is not sure to get the result with the least error. Through the uncertainty analysis of CFD results, it is helpful to find a method to improve the accuracy of the numerical results.
10
Wang, Zhenfeng, Peigang Yan, Hongfei Tang, Hongyan Huang und Wanjin Han. „The Simulation Study of Turbulence Models for Conjugate Heat Transfer Analysis of a High Pressure Air-Cooled Gas Turbine“. In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22088.
Der volle Inhalt der QuelleAnnotation:
The different turbulence models are adopted to simulate NASA-MarkII high pressure air-cooled gas turbine. The experimental work condition is Run 5411. The paper researches that the effect of different turbulence models for the flow and heat transfer characteristics of turbine. The turbulence models include: the laminar turbulence model, high Reynolds number k-ε turbulence model, low Reynolds number turbulence model (k-ω standard format, k-ω-SST and k-ω-SST-γ-θ) and B-L algebra turbulence model which is adopted by the compiled code. The results show that the different turbulence models can give good flow characteristics results of turbine, but the heat transfer characteristics results are different. Comparing to the experimental results, k-ω-SST-θ-γ turbulence model results are more accurate and can simulate accurately the flow and heat transfer characteristics of turbine with transition flow characteristics. But k-ω-SST-γ-θ turbulence model overestimates the turbulence kinetic energy of blade local region and makes the heat transfer coefficient higher. It causes that local region temperature is higher. The results of B-L algebra turbulence model show that the results of B-L model are accurate besides it has 4% temperature error in the transition region. As to the other turbulence models, the results show that all turbulence models can simulate the temperature distribution on the blade pressure surface except the laminar turbulence model underestimates the heat transfer coefficient of turbulence flow region. On the blade suction surface with transition flow characteristics, high Reynolds number k-ε turbulence model overestimates the heat transfer coefficient and causes the blade surface temperature is high about 90K than the experimental result. Low Reynolds number k-ω standard format and k-ω-SST turbulence models also overestimate the blade surface temperature value. So it can draw a conclusion that the unreasonable choice of turbulence models can cause biggish errors for conjugate heat transfer problem of turbine. The combination of k-ω-SST-γ-θ model and B-L algebra model can get more accurate turbine thermal environment results. In addition, in order to obtain the affect of different turbulence models for gas turbine conjugate heat transfer problem. The different turbulence models are adopted to simulate the different computation mesh domains (First case and Second case). As to each cooling passages, the first case gives the wall heat transfer coefficient of each cooling passages and the second case considers the conjugate heat transfer course between the cooling passages and blade. It can draw a conclusion that the application of heat transfer coefficient on the wall of each cooling passages avoids the accumulative error. So, for the turbine vane geometry models with complex cooling passages or holes, the choice of turbulence models and the analysis of different mesh domains are important. At last, different turbulence characteristic boundary conditions of turbine inner-cooling passages are given and K-ω-SST-γ-θ turbulence model is adopted in order to obtain the effect of turbulence characteristic boundary conditions for the conjugate heat transfer computation results. The results show that the turbulence characteristic boundary conditions of turbine inner-cooling passages have a great effect on the conjugate heat transfer results of high pressure gas turbine.
Berichte der Organisationen zum Thema "SST k-ω turbulence model"
1
Bigdeli, Mohammad, und Vahid Monfared. Investigation and Comparison of Stall Angle of Airfoil NACA 0012 in Reynolds Number of 3 × 106 with K‑ω SST, Realizable k‑ε, Spalart-Allmaras Turbulence Models. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, März 2020. http://dx.doi.org/10.7546/crabs.2020.03.13.
Der volle Inhalt der Quelle