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1
Content available Comparison of pressure-loss evaluation fidelity in turbulent energy dissipation models of poppet check valves using computational fluid dynamics (CFD) software
Kobielski Maciej. J., Skarka Wojciech, Skarka Michał
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2024
|
Vol. 27
19--31
EN
Check valves are critical components of fluid systems and have various applications, including house appliances. This article presents a methodology for mapping geometry-specific constriction pressure loss as a function of flow and turbulence in a check valve. This study aimed to gain insight on which Ansys Fluent available turbulent energy dissipation model should be used for further design optimization. This methodology consists of a statistical comparison of computational fluid dynamics (CFD) simulation results obtained using the turbulent energy dissipation models. The key components of the simulation process are discussed. The study’s main results are a comparison of empirical results among flow models’ estimated pressure loss, shown as a function of flow rate in specific geometry and identification of the most suitable model for the considered application. This study concludes that the K-Epsilon (Standard) model best represents the empirically measured behavior of naturally occurring flow energy losses in the considered geometry.
2
Content available Feasibility study of RANS in predicting propeller cavitation in behind-hull conditions
Zhang Yuxin, Wu Xiao-ping, Lai Ming-yan, Zhou Guo-ping, Zhang Jie
Polish Maritime Research
|
2020
|
nr 4
26--35
EN
The propeller cavitation not only affects the propulsive efficiency of a ship but also can cause vibration and noise. Accurate predictions of propeller cavitation are crucial at the design stage. This paper investigates the feasibility of the Reynolds-averaged Navier–Stokes (RANS) method in predicting propeller cavitation in behind-hull conditions, focusing on four aspects: (i) grid sensitivity; (ii) the time step effect; (iii) the turbulence model effect; and (iv) ability to rank two slightly different propellers. The Schnerr-Sauer model is adopted as the cavitation model. A model test is conducted to validate the numerical results. Good agreement on the cavitation pattern is obtained between the model test and computational fluid dynamics. Two propellers are computed, which have similar geometry but slightly different pitch ratios. The results show that RANS is capable of correctly differentiating the cavitation patterns between the two propellers in terms of the occurrence of face cavitation and the extent of sheet cavitation; moreover, time step size is found to slightly affect sheet cavitation and has a significant impact on the survival of the tip vortex cavitation. It is also observed that grid refinement is crucial for capturing tip vortex cavitation and the two-equation turbulence models used – realizable k-ε and shear stress transport (SST) k-ω – yield similar cavitation results.
3
Content available remote On one simulation method of turbulent flows
Pavlenko Anastasiya A., Nadrygailo Tatyana Z.
Journal of New Technologies in Environmental Science
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2019
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Vol. 3, nr 4
169--178
EN
The article deals with the method of turbulent flows modeling with the help of turbulence models, which have the form of algebraic expressions. In well-known numerical simulation systems such models were not used to simulate the flowing of viscous liquid. The proposed models of turbulence make it possible to simplify the software implementation of the equations describing the turbulent behavior of fluid flowing and increase the speed of computation. The developed system of the computer modelling using the specified models, has the simple and clear interface, takes a little space on a disk, is undemanding to system resources, can be supplemented with new problems at plug-in level. The obtained results of computer simulation of liquid flowing around solids of different shapes confirm the adequacy of the turbulence models used. It allows to apply them for modeling turbulent flows at the solution of practical problems.
4
Content available The Influence of the Selected Turbulence Model and Grid Density Degree on the Results of Velocity Distribution Obtained with the Use of the Simulation Program SSIIM
Hammerling M., Walczak N., Nieć J.
Journal of Ecological Engineering
|
2018
|
Vol. 19, nr 3
106--114
EN
This paper analyzed the water flow parameters in the local scour created after building stones sills No 3 km 480 + 902 and 4 km 479 + 225 below the Jeziorsko reservoir on the river Warta. The analysis was carried out using the result of field measurements (velocity distributions) and SSIIM (freeware) software. The study of the geometry of the local scour, were used to create a numerical model and implementing it to the SSIIM software. In the research, the impact of grid density on the obtained results was estimated. The results included the qualitative and quantitative assessment. The conducted analysis can be used to determine the movement of sediment in local scour, and can predict the development in time, and also specify the sill stability under different conditions of the water flow.
5
Content available Numerical analysis of the steam flow past the turbine blade stage
Rogowski K., Pawlicki J.
Journal of Machine Engineering
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2017
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Vol. 17, No. 2
102--110
EN
The steam flow past a last stage (the eleventh stage) of the high pressure part of the TK120 steam turbine was investigated using computational fluid dynamics (CFD). The simulations are performed using the unsteady compressible Navier-Stokes equations. Viscous steam flow has been analyzed using the Spalart-Allmaras turbulence model. The paper presents distributions of instantaneous flow parameters around turbine blades as well as instantaneous aerodynamic blade loads. Flow parameters such as: velocity and static pressure are presented as contour maps whereas aerodynamic loads, axial and circumferential, are given as functions of time. Theoretical power of the examined turbine stage is 4.11 MW. Based on the numerical investigations the power of the analyzed stage is evaluated to be 3.5 MW. All presented in this paper results have been performed using the ANSYS Fluent solver.
6
Content available Design and simulation of an air conditioning project in a hospital based on computational fluid dynamics
Ding X. R., Guo Y. Y., Chen Y. Y.
Archives of Civil Engineering
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2017
|
Vol. 63, nr 2
23--38
EN
This study aims to design a novel air cleaning facility which conforms to the current situation in China, and moreover can satisfy our demand on air purification under the condition of poor air quality, as well as discuss the development means of a prototype product. Air conditions in the operating room of a hospital were measured as the research subject of this study. First, a suitable turbulence model and boundary conditions were selected and computational fluid dynamics (CFD) software was used to simulate indoor air distribution. The analysis and comparison of the simulation results suggested that increasing the area of air supply outlets and the number of return air inlets would not only increase the area of unidirectional flow region in main flow region, but also avoid an indoor vortex and turbulivity of the operating area. Based on the summary of heat and humidity management methods, the system operation mode and relevant parameter technologies as well as the characteristics of the thermal-humidity load of the operating room were analyzed and compiled. According to the load value and parameters of indoor design obtained after our calculations, the airflow distribution of purifying the air-conditioning system in a clean operating room was designed and checked. The research results suggested that the application of a secondary return air system in the summer could reduce energy consumption and be consistent with the concept of primary humidity control. This study analyzed the feasibility and energy conservation properties of cleaning air-conditioning technology in operating rooms, proposed some solutions to the problem, and performed a feasible simulation, which provides a reference for practical engineering.
PL
Przedmiotem tego badania była czysta sala operacyjna. Zastosowano technologię czystej klimatyzacji. Obciążenie chłodnicze czystej klimatyzacji w okresie letnim zostało obliczone przy użyciu praktycznej metody obciążenia chłodniczego klimatyzacji oraz oprogramowania służącego do obliczania zużycia energii. Wyniki obliczeń zostały porównane i przeanalizowane. Model rozprowadzania powietrza był symulowany za pomocą Airpak 3.0, a symulowane wyniki zostały przeanalizowane.
7
Content available CFD analysis of agricultural aircraft aerodynamic characteristics
Dziubiński A., Jaśkowski P., Seredyn T.
Prace Instytutu Lotnictwa
|
2016
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Nr 4 (245)
312--337
EN
This work is a preliminary part of project concerning the water droplets simulation in agricultural aircraft wake. The CFD results of flow calculation resulting in the aerodynamic characteristics of typical agricultural aircraft, on the example of PZL-106 “Kruk”, are presented in an operational range of the angle of attack and the sideslip angle. To obtain those characteristics a commercial RANS code was used. The two commonly utilized turbulence models: K-w SST and Spalart-Allmaras are compared in terms of quantitative and qualitative results, especially in range of parameters when a flow separation occurs. The conclusions about range of use for both models are withdrawn. In order to obtain the flight configuration and conditions for final crop dusting simulation, the complete steady aerodynamic properties of the aircraft have been calculated, described and are available for other studies. Where available, the characteristics are compared with the experimental results. The results are also provided in form of distribution on the predefined aircraft parts, which is hard to obtain with the use of wind tunnel tests.
PL
Praca stanowi część prac przygotowawczych do analiz ruchu kropel wody w zaburzeniu za samolotem rolniczym w trakcie oprysku. Zamieszczono tu rezultaty symulacji numerycznych opływu wokół typowego samolotu rolniczego. Używając jako przykładu samolotu PZL-106 „Kruk" otrzymano charakterystyki aerodynamiczne w funkcji kąta natarcia i kąta ślizgu dla użytkowych zakresów tych parametrów. Do obliczeń użyto komercyjnego kodu z zakresu obliczeniowej mechaniki płynów, który rozwiązywał równania Naviera - Stokesa metodą uśrednień Reynoldsa (RANS), wykorzystując przy tym dwa modele turbulencji: K-w SST oraz Spalart- Allmaras. W pracy porównano oba te modele i przedstawiono wnioski co do zakresu ich zastosowania. W celu uzyskania prawidłowej konfiguracji przelotowej w trakcie oprysku otrzymano drogą obliczeniową kompletne statyczne charakterystyki aerodynamiczne badanego samolotu. Gdzie było to możliwe, porównano je z posiadanymi wynikami eksperymentalnymi. Wyniki te są przedstawione również w postaci udziałów poszczególnych elementów płatowca, które trudno byłoby uzyskać na drodze eksperymentu tunelowego.
8
Content available Ocena wpływu modelu burzliwości na wyniki symulacji numerycznych przepływu wielofazowego w zbiorniku z mieszadłem CD 6
Musiał M., Karcz J.
Inżynieria i Aparatura Chemiczna
|
2015
|
Nr 6
342--343
PL
Badania miały na celu określenie wpływu modelu burzliwości (k-ε, SST) na wyniki symulacji numerycznych (prędkość cieczy, udział gazu zatrzymanego w cieczy, rozmiar pęcherzy gazowych) przepływu dwufazowego wodny roztwór sacharozy – powietrze. Symulacje numeryczne przeprowadzono w zbiorniku o średnicy wewnętrznej D = 0,288 m zaopatrzonym w mieszadło CD 6. Na podstawie przeprowadzonych badań stwierdzono, że zastosowany w obliczeniach model burzliwości ma znaczący wpływ na średni rozmiar pęcherzy gazu.
EN
The aim of this study was to determine the effect of turbulence model (k-ε, SST) on numerical simulation results (liquid velocity, gas hold-up and bubble size) in the two-phase saccharose solution – air flow system. Simulations were carried out for a vessel of inner diameter equal to 0.288 m, equipped with the CD 6 impeller. The results showed that the turbulence model used in computations has a significant impact on the size of gas bubbles.
9
Content available Зоны с отрицательной вихревой вязкостью в продольно-однородных турбулентных потоках
Vysockij L. I.
Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo
|
2012
|
Z. 18 (168)
263--271
PL
W artykule przedstawiono analizę teoretyczną modeli podłużno-jednolitych turbulentnych przepływów w celu udoskonalenia obliczanych schematów i zwiększenia dokładności wyników technicznych. Na podstawie dokonanych obliczeń ustalono, że w istniejących modelach struktury podłużno-jednolitych turbulentnych przepływów nie bierze się pod uwagę warstwy, w której energia kinetyczna turbulencji zmienia się z ruchu turbulentnego do średniego. Zaproponowano wprowadzenie cienkiej warstwy z przepływem przy istnieniu ujemnej lepkości.
EN
This article presents a theoretical analysis of oblong-uniform turbulent flow models in order to improve the calculated patterns and increase the accuracy of technical results. Based on the calculations it was found that the existing models of the structure of oblong-uniform flow do not take into account the layer where the kinetic energy turbulence changes from turbulent flow to medium. It is proposed to place a thin layer with flow, to create the existence of a negative spun viscosity.
10
Content available remote The effect of the turbulence model on the turbine stage flow exit angle distribuation
Świrydczuk J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
|
2012
|
Vol. 16, No 3-4
239--252
EN
The article analyses the effect of the turbulence model on the calculated exit angles of the flow leaving the rotor of a low-pressure turbine stage. Three turbulence models were taken into account: the algebraic Baldwin-Lomax model and two advanced differential models based on the Shear Stress Transport (SST) approach proposed by Menter. The calculated results have revealed that even such extremely different turbulence models impose little difference in the resultant averaged flow exit angle distributions, especially in stages in which a regular flow pattern without flow separation and/or other irregularities is observed. Larger differences can be observed in local distributions of this parameter, especially in the regions of activity of secondary vortex structures.
11
Content available remote The analysis of turbulent flow structure in a free jet
Bartoszewicz J.
International Journal of Applied Mechanics and Engineering
|
2009
|
Vol. 14, no 4
917-928
EN
The paper presents the results of numerical calculations and experimental investigations of free jets under variable turbulence in the jet outlet. The research concerns two cases: the issue of an unstimulated axisymmetric jet to stationary surroundings and the impinge of an unstimulated jet on a flat fixed surface. The results of the numerical calculations have been presented in graphs showing the impact of the changes in the initial turbulence on the structure of the turbulence in the jet. A comparison of the numerical calculations with own results of the experimental investigations has been made for selected cases.
12
Content available remote Effectivity of two-equation turbulence model in impinging jet in short nozzle to surface distance
Bartoszewicz J., Bogusławski L.
International Journal of Applied Mechanics and Engineering
|
2009
|
Vol. 14, no 2
337-347
EN
Results of numerical analysis of a turbulent flow in an impinging air jet have been presented. Numerical simulations of a turbulent flow will be compared with measurements data. Results of calculations for different turbulence models have been analyzed. The Phoenics program developed by CHAM Ltd. will be used for numerical calculation. Five different two-equation models of turbulence will be tested in a selected configuration. The impinging jet turbulent flow was measured in an open wind tunnel using constant temperature anemometer.
13
Content available remote Mathematical Modelling of Pneumatic Melt Spinning of Isotactic Polypropylene. Part 1, Modelling of the Air Jet Dynamics
Zachara A., Lewandowski Z.
Fibres & Textiles in Eastern Europe
|
2008
|
Vol. 16, no. 4 (69)
17--23
EN
In this series of publications, the process of nonwoven melt blowing of ultra-fine fibers is presented. The process starts in the dual slot die where two converging air jets draw the molten polymer stream. In the present paper (Part I), the air flow field is investigated with the aid of the k – ε turbulence model, which is solved numerically. From the results of computations, we have distributions of the air flow parameters along the z – axis, which is also the axis of pneumatic melt spinning. These parameters are the air velocity, temperature and pressure, which will be used in Part II and III to compute the fiber melt blowing dynamics.
PL
Praca stanowi część pierwszą serii trzech publikacji, w których przedstawiono matematyczne modelowanie procesu pneumatycznego przędzenia włóknin ze stopionego polimeru typu „melt blowing”. Proces ten zachodzi pod wpływem podwójnego, zbieżnego strumienia gorącego powietrza wydmuchiwanego symetryczne z dysz powietrznych z obu stron belki przędzalniczej. W niniejszej publikacji (Część I) przedstawiono badanie pola aerodynamicznego strumienia powierza metodą numeryczną z zastosowaniem modelu turbulentnego k – ε. W wyniku obliczeń otrzymano rozkłady parametrów pola przepływu powietrza wzdłuż centralnej osi strumienia, która jest też osią przędzenia. Parametrami tymi są prędkość, temperatura i ciśnienie powietrza, których rozkłady wzdłuż osi przędzenia będą zastosowane w modelowaniu dynamiki procesu pneumatycznego przędzenia włóknin ze stopu izotaktycznego polipropylenu w częściach II i III serii publikacji.
14
Content available A turbulence model for 3-d flows with anisotropic structure of turbulence
Czernuszenko W., Rylov A.
Archives of Hydro-Engineering and Environmental Mechanics
|
2005
|
Vol. 52, nr 4
303-320
EN
A new turbulence model for flows in open channels with compound cross-sections is presented. The structure of turbulence in these channels can be anisotropic. This structure is described by the turbulent stress tensor that is presented here as the sum of two tensors, namely, normal and shear stress tensors. The normal and shear turbulent stresses are expressed by the turbulence intensities and the mixing length tensor (MLT), respectively. The turbulence intensities can be learned from measurements or another suitable approaches. One such approach that allows calculating the main component of the normal stresses is presented in the paper. The components of MLT are defined based on a new concept of generic mixing length (GML). The generic mixing length is assumed to depend on both distances; from the nearest wall and from the water surface. To demonstrate how the new model works the basic hydrodynamic equations (parabolic approximation of Reynolds equations) together with the turbulence model are solved. The well-known Patankar and Spalding (1972) algorithm was used when solving these equations. A series of numerical simulations were performed for different components of MLT and different channel geometries.
15
Content available Comparison of five depth-averaged 2-d turbulence models for river flows
Wu W., Wang P., Chiba N.
Archives of Hydro-Engineering and Environmental Mechanics
|
2004
|
Vol. 51, nr 2
183-200
EN
In this study, five depth-averaged 2-D turbulence models for river flows, including the depth-averaged parabolic eddy viscosity model, modified mixing length model, standard k-e turbulence model, non-equilibrium k-e turbulence model and re-normalized group (RNG) k-e turbulence model, are compared in the simulation of flows around a spur-dyke, in a sudden-expanded flume and in two natural rivers. It is shown that in the two field cases where the channel geometries are simple, all five models can give generally good predictions for the main flow features. However, in the two laboratory cases where the channel geometries are complex, differences have been found among these models. The depth-averaged parabolic eddy viscosity model over-predicts the recirculation flows behind the spur-dyke and the flume expansion. The modified mixing length model gives better prediction than the depth-averaged parabolic model. The standard k-e turbulence model predicts well for the recirculation flow in the sudden-expended flume, but under-predicts the length of recirculation zone behind the spur-dyke, while the non-equilibrium and RNG k-e turbulence models provide good results for both laboratory cases.
16
Modelowanie numeryczne turbulentnego przepływu hydromieszniny Binghama
Bartosik A.,S.
Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika
|
1999
|
Z. 70
7-14
PL
W pracy wykorzystano hipotezę Wilson'a-Thomas'a, opisującą efektywny współczynnik dynamicznej lepkości w hydromieszaninie Binghama. Hipoteza ta zakłada, że w turbulentnym przepływie hydromieszaniny Binghama formuje się podwarstwa lepka, której rozmiar jest większy w stosunku do analogicznego przepływu cieczy newtonowskiej. Opisując lepkość za pomocą hipotezy Wilson'a-Thomas's, zaproponowano modyfikację standardowego modelu turbulencji k-Ε. Modyfikacji poddano funkcję opisującą tłumienie turbulencji przy ścianie stałej. W jej zapisie zaproponowano uwzględnienie naprężenia granicznego w taki sposób, że gdy naprężenie graniczne osiąga wartość zero, to funkcja ta jest identyczna jak w standardowym modelu turbulencji. Stałe modelu turbulencji pozostawiono bez zmian. Ostatecznie model matematyczny, opisujący przepływ w pełni rozwinięty, stanowi układ trzech równań różniczkowych cząstkowych. Wyniki obliczeń numerycznych globalnych parametrów zweryfikowano z dostępnymi wynikami badań eksperymentalnych otrzymując satysfakcjonującą zgodność.
EN
In the present work Wilson-Thomas hypotheses is used, which describes effective viscosity coefficient in Bingham slurry flow. The hypotheses based on an assumption that in in Bingham slurry flow the viscous sublayer becomes thicker. Modified k-Ε turbulence model, in which yield stress is introduced in damping function, was used in prediction of hydraulic losses. The turbulence model constants were the same like in standard turbulence model. Mathematical model consists set of there partial differential equations. Results of numerical perdictions were compared with experimental data of Bingham slurry flow yield stress. Comparison confirmed good agreement between predictions and measurements.
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