Influence of Mesh Density and Turbulence Models on 2D Viscous Flutter in 11th Standard Configuration

2012 ◽  
Author(s):  
Aleksandra Pajak ◽  
Romuald Rzadkowski
Keyword(s):  
Large Deviations ◽  
Numerical Simulations ◽  
Qualitative Agreement ◽  
Phase Distribution ◽  
Turbulence Models ◽  
Experimental Results ◽  
Pressure Amplitude ◽  
Ansys Cfx ◽  
Mesh Density ◽  
Standard Configuration

In this study, numerical simulations of 2D viscous flutter were performed and compared with the available experimental results for different mesh density and different turbulence models. The calculations were carried out for bending oscillations of the cascade known as the Eleventh Standard Configuration. The ANSYS CFX v.12.1 code with SST, SA, k-ω turbulence models was used for calculations with various values of the inter-blade phase angle. Three moving H-O grids were used. Comparison of the calculated and the experimental results for the Eleventh Standard Configurations for the IBPA = 180 deg has shown good quantitative and qualitative agreement for local performances (unsteady pressure amplitude and phase distribution). For the IBPA = 90 and −90 deg the results are correct only in terms of amplitude. The phase distribution showed large deviations. The effect of various grids as well as SST, Spalart Allmaras and k-ω turbulence models was not significant in the subsonic case, but it turned out to be very noticeable in the transonic case.

3D Viscous Flutter in Turbomachinery Cascade by Godunov-Kolgan Method

2006 ◽  
Author(s):  
Romuald Rza¸dkowski ◽  
Vitally Gnesin ◽  
Luba Kolodyazhnaya
Keyword(s):  
Qualitative Agreement ◽  
Phase Distribution ◽  
Experimental Results ◽  
Navier Stokes ◽  
Finite Volume Scheme ◽  
Pressure Amplitude ◽  
Navier Stokes Equation ◽  
Structured Grid ◽  
Standard Configuration ◽  
Benchmark Solutions

In this study, numerical simulations of 3D viscous flutter were performed and compared with the available experimental results. The calculations were carried out for bending oscillations of the cascade known as the Eleventh Standard Configuration. The developed numerical algorithm solves the 3D Reynolds-averaged Navier-Stokes equation together with the Baldwin-Lomax turbulence model, using the explicit monotonous second-order accurate Godunov-Kolgan finite-volume scheme and moving hybrid H-O structured grid. Comparison of the calculated and the experimental results for the Eleventh Standard Configurations has shown sufficient quantitative and qualitative agreement for local performances (unsteady pressure amplitude and phase distribution) at off-design conditions. Benchmark solutions are provided for various values of the inter-blade phase angle.

scholarly journals Assessment of different turbulence models in simulating axisymmetric flow in suddenly expanded nozzles

2018 ◽  
Vol 7 (3.29) ◽  
pp. 243
Author(s):  
Sher Afghan Khan ◽  
Mir Owais Ali ◽  
Miah Mohammed Riyadh ◽  
Zahid Hossen ◽  
Nafis Mahdi Arefin
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Mach Number ◽  
Numerical Simulations ◽  
Axisymmetric Flow ◽  
Turbulence Models ◽  
Experimental Results ◽  
Nozzle Flow ◽  
Axisymmetric Nozzle ◽  
Good Agreement

A numerical simulation was carried out to compare various turbulence models simulating axisymmetric nozzle flow past suddenly expanded ducts. The simulations were done for L/D = 10. The convergent-divergent nozzle has been modeled and simulated using the turbulence models: The Standard k-ε model, The Standard k-ω model and The SST k-ω model. Numerical simulations were done for Mach numbers 1.87, 2.2, and 2.58 and the nozzles were operated for NPRs in the range from 3 to 11. From the numerical analysis it is apparent that for a given Mach number and effect of NPR will result in maximum gain or loss of pressure. Numerical results are in good agreement with the experimental results.  

scholarly journals Thermal-hydraulics validation of CFD code for light water nuclear reactors against benchmark experimental results

2021 ◽  
Vol 9 (2B) ◽  
Author(s):  
Deiglys Borges Monteiro ◽  
Duvan Alejandro Castellanos Gonzalez ◽  
José Rubens Maiorino
Keyword(s):  
Fuel Element ◽  
Numerical Simulations ◽  
Nuclear Reactor ◽  
High Accuracy ◽  
Experimental Results ◽  
Thermal Hydraulics ◽  
Light Water ◽  
Loss Of Coolant Accident ◽  
Ansys Cfx ◽  
Water Reactors

The cooling of a nuclear reactor depends on a suitable fluid flow pattern among its fuel elements aiming the removal of heat produced in the fuel. In case of light water reactors, an excess of heat drives the fluid to change its phase from liquid to vapor, significantly reducing its capacity to remove heat and leading the reactor to a Loss of Coolant Accident. Numerical simulations using a CFD code is a suitable tool to address this kind of problem and explore the conditions that should be avoided during the reactor operation. The commercial CFD codes had proven to be reliable to simulate with a high accuracy and confidence the thermal-hydraulics of a sort of equipment and systems, avoiding spending efforts and financial resources in the development of new codes that, essentially, perform the same tasks. Despite of it, the CFD codes must be validated, such as against experimental results. To comply with this objective, a benchmark fuel element was purposed and experimentally essayed to provide experimental results for CFD codes calibration. The results of this essay are provided to the four types of subchannels for a 5x5 PWR fuel element, with results provided as density and void fraction. This work presentes the preliminary results obtained with CFD numerical simulations using the ANSYS-CFX® code for the central subchannel with active rods for stead state operation. The results demonstrated that the ANSYS-CFX® is adequate to simulate with high accuracy the flow in this subchannel.

Numerical Investigation of Fluid Flow Parameters in a Combustor Simulator

2018 ◽  
Author(s):  
Darioush G. Barhaghi ◽  
Lars Hedlund
Keyword(s):  
Gas Turbines ◽  
Cooling System ◽  
Turbulence Models ◽  
Experimental Results ◽  
Computational Domain ◽  
Flow Parameters ◽  
Hot Air ◽  
Ansys Cfx ◽  
University Of Florence ◽  
The University

In recent years computational fluid dynamics (CFD) is substantially employed in the design process of gas turbines. To increase the performance of the turbines an efficient cooling system design is essential. This is largely dependent on the accuracy of the predicted temperature at the exit of the combustor. Lack of accuracy of the predicted temperature at the combustor-turbine interface results in using large safety factors which affect the performance negatively. It is believed that the RANS methods are incapable of predicting the mixing process in highly swirling flows in the combustors. In this study the flow in a none-reactive model combustor simulator is investigated numerically using RANS, SAS and LES turbulence models in ANSYS CFX code. The model combustor consists of three swirling mixers through which the hot air passes. The cold air that goes through many small effusion holes of the outer and inner liners mixes up with the swirling hot air. The computational domain however consists only of one sector and periodic boundary condition is applied in the circumferential direction. The numerical results are compared with the experimental results that are provided by the University of Florence as part of the European FACTOR project. It is confirmed that the RANS or URANS methods are not capable of reproducing the experimental results.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

The Effect of Different Turbulence Models on the Emitter Discharge by Using Computational Fluid Dynamics

2013 ◽  
Vol 662 ◽  
pp. 586-590
Author(s):  
Gang Lu ◽  
Qing Song Yan ◽  
Bai Ping Lu ◽  
Shuai Xu ◽  
Kang Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Turbulence Models ◽  
Experimental Results ◽  
Turbulent Model ◽  
Simulation Results ◽  
Rsm Model ◽  
Dynamics Method ◽  
Emitter Discharge

Four types of Super Typhoon drip emitter with trapezoidal channel were selected out for the investigation of the flow field of the channel, and the CFD (Computational Fluid Dynamics) method was applied to simulate the micro-field inside the channel. The simulation results showed that the emitter discharge of different turbulent model is 4%-14% bigger than that of the experimental results, the average discharge deviation of κ-ω and RSM model is 5, 4.5 respectively, but the solving efficiency of the κ-ω model is obviously higher than that of the RSM model.

Additive manufacturing of pure copper: From numerical simulations to experimental results

2021 ◽  
Author(s):  
Hagen Kohl ◽  
Lisa Schade ◽  
Gabor Matthäus ◽  
Tobias Ullsperger ◽  
Burak Yürekli ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Numerical Simulations ◽  
Pure Copper ◽  
Experimental Results

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

Effect of Ramp Angle on the Anti-Loosening Ability of Wedge Self-Locking Nuts Under Vibration

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jianhua Liu ◽  
Hao Gong ◽  
Xiaoyu Ding
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Production Technology ◽  
Material Properties ◽  
Threshold Value ◽  
Commercial Production ◽  
Experimental Results ◽  
Fe Method ◽  
Transversal Vibration

Recently, the wedge self-locking nut, a special anti-loosening product, is receiving more attention because of its excellent reliability in preventing loosening failure under vibration conditions. The key characteristic of a wedge self-locking nut is the special wedge ramp at the root of the thread. In this work, the effect of ramp angle on the anti-loosening ability of wedge self-locking nuts was studied systematically based on numerical simulations and experiments. Wedge self-locking nuts with nine ramp angles (10 deg, 15 deg, 20 deg, 25 deg, 30 deg, 35 deg, 40 deg, 45 deg, and 50 deg) were modeled using a finite element (FE) method, and manufactured using commercial production technology. Their anti-loosening abilities under transversal vibration conditions were analyzed based on numerical and experimental results. It was found that there is a threshold value of the initial preload below which the wedge self-locking nuts would lose their anti-loosening ability. This threshold value of initial preload was then proposed for use as a criterion to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively and to determine the optimal ramp angle. Based on this criterion, it was demonstrated, numerically and experimentally, that a 30 deg wedge ramp resulted in the best anti-loosening ability among nine ramp angles studied. The significance of this study is that it provides an effective method to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively, and determined the optimal ramp angle in terms of anti-loosening ability. The proposed method can also be used to optimize other parameters, such as the material properties and other dimensions, to guarantee the best anti-loosening ability of wedge self-locking nuts.

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