scholarly journals Scale-adaptive simulation of wind turbines, and its verification with respect to wind tunnel measurements

2018 ◽  
Author(s):  
Jiangang Wang ◽  
Chengyu Wang ◽  
Filippo Campagnolo ◽  
Carlo L. Bottasso
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Computational Cost ◽  
Turbulence Models ◽  
Computational Burden ◽  
Eddy Simulation ◽  
Adaptive Simulation ◽  
Large Eddy ◽  
Order Of Magnitude ◽  
Interesting Alternative

Abstract. This paper considers the application of a scale-adaptive simulation (SAS) CFD formulation for the modeling of single and waked wind turbines in flows of different turbulence intensities. The SAS approach is compared to a large-eddy simulation (LES) formulation, as well as to experimental measurements performed in a boundary layer wind tunnel with scaled wind turbine models. The motivation for the use of SAS is its significantly reduced computational cost with respect to LES, made possible by the use of less dense grids. Results indicate that the two turbulence models yield in general results that are very similar, in terms of rotor-integral quantities and wake behavior. The matching is less satisfactory in very low turbulence inflows. Given that the computational cost is about one order of magnitude smaller, SAS is found to be an interesting alternative to LES for repetitive runs where one can sacrifice a bit of accuracy for a reduced computational burden.

scholarly journals Effect of Local Grid Refinement on Performance of Scale-Resolving Models for Simulation of Complex External Flows

Aerospace ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 86 ◽  
Author(s):  
Amne ElCheikh ◽  
Michel ElKhoury
Keyword(s):  
Computational Cost ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Pollutant Dispersion ◽  
Uniform Grid ◽  
Grid Refinement ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Uniform Grids ◽  
Large Eddy

Numerical simulations are crucial for fast and accurate estimations of the flow characteristics in many engineering applications such as atmospheric boundary layers around buildings, external aerodynamics around vehicles, and pollutant dispersion. In the simulation of flow over urban-like obstacles, it is crucial to accurately resolve the flow characteristics with reasonable computational cost. Therefore, Large Eddy Simulations on non-uniform grids are usually employed. However, an undesirable accumulation of energy at grid-refinement interfaces was observed in previous studies using non-uniform grids. This phenomenon induced oscillations in the spanwise velocity component, mainly on fine-to-coarse grid interfaces. In this study, the two challenging test cases of flow over urban-like cubes and flow over a 3-D circular cylinder were simulated using three different scale-resolving turbulence models. Simulations were performed on uniform coarse and fine grids on one hand, and a non-uniform grid on the other, to assess the effect of mesh density and mesh interfaces on the models’ performance. Overall, the proposed One-Equation Scale-Adaptive Simulation (One-Equation SAS) showed the least deviation from the experimental results in both tested cases and on all grid sizes and types when compared to the Shear Stress Transport-Improved Delayed Detached Eddy Simulation (IDDES) and the Algebraic Wall-Modeled Large Eddy Simulation (WMLES).

scholarly journals Turbulence Models for Simulation of the Flow in a Rotor-Stator Cavity

2019 ◽  
Vol 213 ◽  
pp. 02104
Author(s):  
Lucie Zemanová ◽  
Pavel Rudolf
Keyword(s):  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Operating Conditions ◽  
Narrow Gap ◽  
Detached Eddy Simulation ◽  
Axial Thrust ◽  
Eddy Simulation ◽  
Adaptive Simulation ◽  
Large Eddy

Modelling of the flow in the cavities between rotor and stator in turbomachines (e.g. pumps or turbines) is a task of great interest. Correctly evaluated pressure and velocity fields enable calculation of the disk losses and therefore assessment of efficiency. It is also crucial for determination of axial thrust and thus design of the bearings. The study demonstrates abilities of various turbulence models to describe the flow in a narrow gap between rotating and stationary disks. Numerical simulations were performed in order to find out the ability of particular models to capture unstable structures appearing during specific operating conditions as well as to calculate the velocity profiles precisely. Large Eddy Simulation (LES), Scale Adaptive Simulation (SAS), Detached Eddy Simulation (DES), Reynolds stress model (RSM) and SST k – ω model were used. Obtained results were also compared with experimental measurement published by Viazzo et al. [1]

scholarly journals Validation study for Large-Eddy Simulation of Forest Flow

2020 ◽  
Vol 207 ◽  
pp. 02010
Author(s):  
George Pitchurov ◽  
Christof Gromke ◽  
Jordan A. Denev ◽  
Flavio Cesar Cunha Galeazzo
Keyword(s):  
Wind Tunnel ◽  
Large Eddy Simulation ◽  
Forest Canopy ◽  
Turbulence Models ◽  
Leading Edge ◽  
Eddy Simulation ◽  
Sink Term ◽  
Large Eddy ◽  
Open Test ◽  
Strong Winds

The publication presents Large-Eddy Simulation (LES) of flow over a reduced-scale wind tunnel model of a forest canopy. The final aim of the study is to determine factors responsible for damage in forests by strong winds. The wind tunnel forest was represented by an open-porous foam material for the crown layer and wooden dowels for the trunk layer. The forest model was installed in the open test section of a Goettingen-type wind tunnel and Particle Image Velocimetry (PIV) measurements were made for the acquisition of the flow field data. The numerical simulations were performed with OpenFOAM®. The forest was modelled by an additional sink term in the momentum transport equations based on the leaf area density and a characteristic drag coefficient for the underlying tree specimen. Large-eddy simulations with different subgrid-scale (SGS) turbulence models were carried out and compared to wind tunnel data. The Smagorinsky SGS model outperformed the dynamic Lagrangian SGS model in the windward edge region (within a distance of approximately 2 tree heights from the leading edge) whereas the dynamic Lagrangian SGS model showed a better performance for regions farther downstream.

scholarly journals A Large-Eddy Simulation Approach for Wind Turbine Wakes and its Verification with Wind Tunnel Measurements

2018 ◽  
Author(s):  
Jiangang Wang ◽  
Chengyu Wang ◽  
Filippo Campagnolo ◽  
Carlo L. Bottasso
Keyword(s):  
Wind Tunnel ◽  
Large Eddy Simulation ◽  
Computational Cost ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Simulation Approach ◽  
Wind Tunnel Experiments ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Turbulence

Abstract. This paper first describes a large-eddy simulation approach, and then verifies it with respect to single-turbine wind tunnel experiments. Various aspects of the numerical approach are considered, to try to reduce its need for tuning, improve its accuracy and limit its computational cost. Simulation results are compared to measurements, including rotor and wake quantities. The study includes normal operating conditions, as well as wake manipulation by derating, yaw misalignment and cyclic pitching of the blades. Results indicate a good overall matching of simulations with experiments. Low turbulence test cases appear to be more challenging than moderate and high turbulence ones, due to the need for denser grids to limit numerical diffusion and accurately resolve tip-shed vortices in the near wake region.

Development of Large-Eddy Simulation for Vehicle Aerodynamics

2002 ◽  
Author(s):  
S. Krajnovic ◽  
L. Davidson
Keyword(s):  
Large Eddy Simulation ◽  
Computational Cost ◽  
Turbulence Models ◽  
Quantitative Prediction ◽  
Eddy Simulation ◽  
Aerodynamic Properties ◽  
Lower Reynolds Number ◽  
Large Eddy ◽  
Flow Features ◽  
Vehicle Aerodynamics

The feasibility of use of large-eddy simulation (LES) in external vehicle aerodynamics is investigated. The computational cost needed for LES of the full size car at road conditions is beyond the capability of the computers in the near future (Krajnovic´ (2002)). Since LES cannot be used for quantitative prediction of this flow, i.e. obtaining the aerodynamic forces and moments, an alternative use of this technique is suggested that can enhance the understanding of the flow around a car. It is found that making LES of the flow around simplified car-like shapes at lower Reynolds number can increase our knowledge of the flow around a car. Two simulations are made, one of the flow around a cube and the other of the flow around a simplified bus. The former simulation proved that LES with relatively coarse resolution and simple inlet boundary condition can provide accurate results. The latter simulation resulted in flow in agreement with experimental observations and displayed some flow features that were not observed in experiments or steady simulations of such flows. This simulation gave us possibility to study the transient mechanisms that are responsible for the aerodynamic properties of a car. The knowledge gained from this simulation can be used by the stylist to tune the aerodynamics of the car’s design but also by the CFD specialists to improve the turbulence models.

scholarly journals Large-eddy simulation of scaled floating wind turbines in a boundary layer wind tunnel

2018 ◽  
Vol 1037 ◽  
pp. 072032
Author(s):  
J Wang ◽  
C Wang ◽  
O D Castañeda ◽  
F Campagnolo ◽  
C L Bottasso
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Large Eddy Simulation ◽  
Wind Turbines ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

Large-eddy simulation of turbulent flow past wind turbines/farms: the Virtual Wind Simulator (VWiS)

Wind Energy ◽  
2014 ◽  
Vol 18 (12) ◽  
pp. 2025-2045 ◽  
Author(s):  
Xiaolei Yang ◽  
Fotis Sotiropoulos ◽  
Robert J. Conzemius ◽  
John N. Wachtler ◽  
Mike B. Strong
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Wind Turbines ◽  
Eddy Simulation ◽  
Flow Past ◽  
Large Eddy

Large Eddy Simulations of a Hydrocyclone

2002 ◽  
Author(s):  
Francisco Jose´ de Souza ◽  
Aristeu Silveira Neto
Keyword(s):  
Turbulence Models ◽  
Fluid Flows ◽  
Scale Model ◽  
Staggered Grid ◽  
Subgrid Scale ◽  
Step Method ◽  
Fractional Step Method ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subgrid Scale Modeling

Subgrid-scale modeling, which characterizes Large Eddy Simulation (LES), has been used to predict the behavior of a water-fed hydrocyclone operating without an air core. The governing equations were solved by a fractional step method on a staggered grid. The Smagorinsky subgrid-scale model was employed to account for turbulent effects. Numerical results actually capture the main features of the flow pattern and agree reasonably well with experiments, suggesting that LES represents an interesting alternative to classical turbulence models when applied to the numerical solution of fluid flows within hydrocyclones.

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