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

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.

2013 ◽  
Vol 444-445 ◽  
pp. 299-303
Author(s):  
Lan Ge ◽  
Wen Rong Hu

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.


Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2134
Author(s):  
Frank Plua ◽  
Victor Hidalgo ◽  
P. Amparo López-Jiménez ◽  
Modesto Pérez-Sánchez

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.


2021 ◽  
Author(s):  
Shan Wang ◽  
C. Guedes Soares

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.


2018 ◽  
Vol 7 (3.17) ◽  
pp. 133
Author(s):  
Mohammad Rasidi Rasani ◽  
Azhari Shamsudeen ◽  
Zambri Harun ◽  
Wan Mohd Faizal Wan Mahmood

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.  


Author(s):  
Adam Kiczko ◽  
Janusz Kubrak ◽  
Elżbieta Kubrak

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.


2015 ◽  
Vol 773-774 ◽  
pp. 353-357
Author(s):  
Kamil Abdullah ◽  
Osama H. Abdulguad ◽  
Akmal Nizam Mohammed ◽  
Zaid Suleiman

Film cooling has been extensively used to provide thermal protection for the external surfaces of gas turbine components. For the past 40 years, numerous number of film cooling hole designs and arrangements have been introduced. Due to broad designs and arrangements of film cooling, numerical investigation has been utilized to provide initial insight on the aerodynamics and thermal performance of the new film cooling designs or arrangements. The present work focuses on the numerical investigation of RANS and URANS analyses on a flat plate film cooling. The investigation aims to provide comparison between various turbulent models available for the Reynolds Average Navier Stokes (RANS) analyses and extended to unsteady Reynolds Average Navier Stokes (URANS). The numerical investigations make used of ANSYS CFX ver. 14 and were carried out at Reynolds Number, Re = 7,000 based on the hole diameter at blowing ratio, BR = 0.5. The results of the RANS analyses show significant influence of the turbulent models on the predicted aerodynamics and thermal performance of the film cooling. The result of URANS indicates limitation of RANS analyses to provide details on the eddied and vortices formation in film cooling flow structure.


Author(s):  
Jing-Wei Jiang ◽  
Wei-Xi Huang

A new kind of advanced submerged propulsion is automatically modeled and analyzed based on the hydrodynamic and cavitation performance. A mathematical algorithm is proposed to describe the fusion-duct, which is controlled by several design parameters, including section diameters, section lengths, and inlet shape and aspect ratio. The hydrodynamic performances of 13 cases with different parameter combinations are numerically simulated. The simulation is carried out by solving the Reynolds Average Navier-Stokes equations with STAR-CCM+, and the SST k-ω turbulence model is applied. The curves of rotor thrust and torque, stator thrust and duct resistance, along with efficiency and merit coefficient are obtained as functions of the advance coefficient and are compared for different cases. Meanwhile, the pressure distribution on both sides of the rotor and the flow field of intermediate section are systematically analyzed. To guide future designs, an impact factor is further defined and calculated to quantify the effects of different parameters. The results indicate that the section diameters have the most significant influence on hydrodynamic and cavitation performances.


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