Hybrid Reynolds-Average Navier-Stokes and Kinetic Eddy Simulation of External and Internal Flows

2010 ◽  
Vol 47 (3) ◽  
pp. 805-811 ◽  
Author(s):  
Mina Zaki ◽  
Suresh Menon ◽  
Lakshmi N. Sankar
Keyword(s):  
Navier Stokes ◽  
Internal Flows ◽  
Reynolds Average Navier Stokes ◽  
Eddy Simulation ◽  
Reynolds Average

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.

Laminarization of Internal Flows Under the Combined Effect of Strong Curvature and Rotation

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
K. M. Guleren ◽  
I. Afgan ◽  
A. Turan
Keyword(s):  
Secondary Flows ◽  
Combined Effect ◽  
Navier Stokes ◽  
Duct Flow ◽  
Internal Flows ◽  
Square Duct ◽  
Eddy Simulation ◽  
Numerical Predictions ◽  
Wide Range ◽  
Strong Curvature

The laminarization phenomenon for the flow under the combined effect of strong curvature and rotation is discussed based on numerical predictions of large-eddy simulation (LES). Initially, the laminarization process is presented for the fully developed flow inside a spanwise rotating straight square duct. LES predictions over a wide range of rotation numbers (Ro=0–5) show that the turbulent kinetic energy decreases monotonically apart from 0.2<Ro<0.5. Subsequently, a spanwise rotating U-duct flow is considered with Ro=±0.2. The interaction of curvature and Coriolis induced secondary flows enhances the turbulence for the negative rotating case, whereas this interaction ensues strong laminarization for the positive rotating case. Finally, the laminarization is presented in the impeller of a typical centrifugal compressor, rotating at a speed of Ω=1862rpm(Ro=0.6). The resulting LES predictions are observed to be better than those of Reynolds-averaged Navier-Stokes (RANS) in the regions where turbulence is significant. However, for the regions dominated by strong laminarization, RANS results are seen to approach those of LES and experiments.

Dynamic Stall Control by Undulatory Deformation

2013 ◽  
Vol 444-445 ◽  
pp. 299-303
Author(s):  
Lan Ge ◽  
Wen Rong Hu
Keyword(s):  
Stokes Equations ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Reynolds Average Navier Stokes ◽  
Navier Stokes Equations ◽  
Stall Angle ◽  
Stall Control ◽  
Reynolds Average ◽  
High Angles Of Attack ◽  
Better Than

Dynamic stall can delay the stall of wings and airfoils that are rapidly pitched beyond the static stall angle. A new method of active dynamic stall control by the undulatory foil was proposed in this paper. The study was based on solving unsteady Reynolds-Average Navier-Stokes equations. Comparisons of the effectiveness of pitching foils and undulatory foils on dynamic stall control in both light stall and deep stall were conducted. The undulatory foils with various controllable parameters were further discussed. The results showed that the performance of undulatory foils is much better than that of the rigid pitching foil at high angles of attack either in the light stall or in the deep stall situation.

scholarly journals Efecto del refinamiento de la descripción de la rugosidad en una aproximación 2D para un río de montaña: un caso de estudio

La Granja ◽  
2021 ◽  
Vol 33 (1) ◽  
pp. 92-102
Author(s):  
Juan Sebastián Cedillo Galarza ◽  
Luis Manuel Timbre Castro ◽  
Esteban Patricio Samaniego Alvarado ◽  
Andrés Omar Alvarado Martínez
Keyword(s):  
Navier Stokes ◽  
Reynolds Average Navier Stokes ◽  
Estimation System ◽  
Reynolds Average

La predicción de niveles de agua en ríos es importante para prevenir pérdidas económicas así como de vidas humanas causadas por inundaciones. Los modelos hidráulicos son comúnmente usados para predecir estos niveles de agua y tomar acciones para mitigar el daño debido a inundaciones. En la presente investigación, se analizó una aproximación 2D para resolver las ecuaciones promediadas en profundidad de Reynolds Average Navier Stokes (RANS), llamado Conveyance Estimation System (CES), para explorar sus capacidades predictivas. Este artículo presenta una ampliación del estudio realizado por Knight et al. (2009). De igual forma, en esta investigación se explora una caracterización más detallada del parámetro de rugosidad y del número de zonas de rugosidad produciendo diversos escenarios. Se evaluó el desempeño de cada escenario mediante diferentes funciones de ajuste usando curvas de descarga para comparación. La investigación muestra que el uso de una adecuada descripción de la rugosidad, como un factor de rugosidad calibrado para toda la sección transversal o un modelo de rugosidad para cantos rodados calibrado para el lecho junto con valores de rugosidad obtenidos en valores sugeridos por el CES para los bancos, produce resultados del modelo óptimos en un río de montaña.

scholarly journals Analysis of Applicability of CFD Numerical Studies Applied to Problem When Pump Working as Turbine

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2134
Author(s):  
Frank Plua ◽  
Victor Hidalgo ◽  
P. Amparo López-Jiménez ◽  
Modesto Pérez-Sánchez
Keyword(s):  
Turbulence Models ◽  
Experimental Tests ◽  
Navier Stokes ◽  
Variable Speed ◽  
Reynolds Average Navier Stokes ◽  
Academic Literature ◽  
Numerical Studies ◽  
Speed Rotation ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Average

The present research depicts an analysis of the implementation of computational fluid dynamics (CFD) in the study of pumps such as turbines and PATs. To highlight the benefits of CFDs for PAT studies, results from both experimental tests have been compared to better understand the reproduction error phenomena. For this, data analysis used in successful models has been applied to determine variables and parameters, and to report a low relative error. The results show that most of the studies focused on fixed speed rotation with some cases of variable speed rotation. Furthermore, there is not enough information in the academic literature for PAT of axial and mixed flows with fixed and variable speed. Finally, turbulence models based on Reynolds average Navier–Stokes (RANS) have been used to simulate PATs with fixed speed rotation in most cases.

Numerical Assessment of Turbulence Effects on Water Entry of a Hemisphere

2021 ◽  
Author(s):  
Shan Wang ◽  
C. Guedes Soares
Keyword(s):  
Water Entry ◽  
Equation Model ◽  
Navier Stokes ◽  
Fluid Models ◽  
Courant Number ◽  
Cfd Simulations ◽  
Reynolds Average Navier Stokes ◽  
Numerical Assessment ◽  
Turbulence Effects ◽  
Reynolds Average

Abstract Water entry of a rigid hemisphere is simulated using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in the open-source library OpenFoam. The solver InterDyMFoam is applied and the algorithm PIMPLE which is a combination of PISO (Pressure Implicit with Splitting of Operators) and SIMPLE (Semi-Implicit Method for pressure-Linked Equations) algorithms are used in the simulations. A second-order backward difference scheme is applied for the temporal discretization. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) using the procedures recommended by ITTC. The comparisons of slamming loads and motions between the CFD simulations are presented using both laminar and turbulence fluid models for the hemisphere entering the water at various speeds. Turbulence is modelled with a Reynolds averaged stress (RAS) k-ω two-equation model. The turbulence effects on the slamming loads will be assessed for the case with different entry velocities.

A Computational Aerodynamic Study of Tandem Rotating Wheels in Contact with the Ground

2018 ◽  
Vol 7 (3.17) ◽  
pp. 133
Author(s):  
Mohammad Rasidi Rasani ◽  
Azhari Shamsudeen ◽  
Zambri Harun ◽  
Wan Mohd Faizal Wan Mahmood
Keyword(s):  
Lift Coefficient ◽  
Rear Wheel ◽  
Front Wheel ◽  
Navier Stokes ◽  
Limited Attention ◽  
Road Vehicles ◽  
Reynolds Average Navier Stokes ◽  
Drag And Lift ◽  
Reynolds Average ◽  
Good Agreement

Wheels have significant impact on noise and drag of road vehicles, which may influence their fuel consumption, emission and comfort. A number of studies have analyzed flow and aerodynamics of isolated wheel in contact with the ground, but limited attention has been given to interaction between wheels. The present study aims to compare the aerodynamics and flow structure between single and tandem wheels. To that end, flow around single and tandem wheels are simulated using a turbulence Scaled Adaptive Unsteady Reynolds Average Navier Stokes (URANS) model. Wheel geometry was based on the actual wheel used in the experiments of Fackrell and Harvey. Flow around single and tandem wheels were examined and compared, along with their respective drag and lift coefficients. Results for single wheel in contact with the ground show good agreement with previous experiments. In the tandem wheel case, the rear wheel exhibits lower drag coefficient (CD = 0.37) and more downforce (lift coefficient CL = -0.14) compared to the front wheel. The present investigation may help to illustrate impact of wheel interaction on their aerodynamics.  

scholarly journals Experimental and numerical investigation of non-submerged flow under a sluice gate

2015 ◽  
Vol 47 (3) ◽  
pp. 187-201 ◽  
Author(s):  
Adam Kiczko ◽  
Janusz Kubrak ◽  
Elżbieta Kubrak
Keyword(s):  
Experimental Data ◽  
Numerical Solution ◽  
Numerical Investigation ◽  
Potential Field ◽  
Complex Form ◽  
Navier Stokes ◽  
Energy Losses ◽  
Sluice Gate ◽  
Reynolds Average Navier Stokes ◽  
Reynolds Average

Abstract The problem of sluice gate flow is analyzed using two models: a simplified one, derived according to the concept of the Potential Field (PF), and a more complex form, based on the Reynolds Average Navier-Stokes (RANS) equations. The numerical solution is compared with experimental data, including measurements performed by authors and results acquired from literature. Despite its simplicity, the PF model provides a satisfactory agreement with the measurements. The slightly worse performance of the RANS model comes from an overestimation of energy losses.

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