Relevant bibliographies by topics / RANS k- model

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers
  5. Reports

Academic literature on the topic 'RANS k- model'

Author: Grafiati
Published: 4 June 2021
Last updated: 6 February 2022

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Journal articles on the topic "RANS k- model"

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Gao, Guo Hua, Jing Zhao, Fei Ma, and Wei Dong Luo. "Hybrid RANS–LES Modeling for Unsteady Cavitating Flow Simulation." Applied Mechanics and Materials 152-154 (January 2012): 1187–90. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.1187.

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A typical hybrid RANS-LES approach, DES (Detached Eddy Simulation), was introduced into cavitating flow simulation in this paper. The applicability of two DES models, including one equation DES model and SST k-ω DES model, and standard k-ε model was analyzed through experimental data of a water tunnel experiment. Validation results illustrate that the precision of DES method depends on the RANS model used and the length scale used to distinguish LES zone and RANS zone. The SST k-ω DES method can well predict cavitating flow. The averaged results gained through this model are better than those of standard k-ε or one equation DES model. By comparison, the one equation DES model shows little advantage than standard k-ε model to simulate cavitating flow.
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Zhang, Xia Wan, Jie Mao та Liang Yu. "A New k-ω Model for Magnetohydrodynamic Turbulent Duct Flow". Applied Mechanics and Materials 865 (червень 2017): 253–56. http://dx.doi.org/10.4028/www.scientific.net/amm.865.253.

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A solver for MHD turbulent flow and a new RANS model based on k-ω model in the open source toolbox OpenFOAM are developed to investigate magnetohydrodynamic (MHD) turbulent flow. Two electro-magnetic terms in the k and ω transport equations are added to include magnetohydrodynamic (MHD) effects. The modified k-ω is validated by simulating MHD turbulent duct flow. Time-averaged velocity and turbulent kinetic energy profiles simulated by standard k-ω and the modified k-ω in the fully developed section are both reported. The results compare fairly with those obtained from DNS data. A difference of 8.4% in is found between the modified k-ω and DNS, but the RANS model only uses 0.4% of the DNS computation time.
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Kim, Byeong-Cheon, and Kyoungsik Chang. "Assessment of Hybrid RANS/LES Models in Heat and Fluid Flows around Staggered Pin-Fin Arrays." Energies 13, no. 14 (2020): 3752. http://dx.doi.org/10.3390/en13143752.

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In the present work, the three-dimensional heat and fluid flows around staggered pin-fin arrays are predicted using two hybrid RANS/LES models (an improved delayed detached eddy simulation (IDDES) model and a stress-blended eddy simulation (SBES) model), and one transitional unsteady Reynolds averaged Navier-Stokes (URANS) model, called k-ω SSTLM. The periodic segment geometry with a total of nine pins is considered with a channel height of 2D and a distance of 2.5D between each pin. The corresponding Reynolds number based on the pin diameter and the maximum velocity between pins is 10,000. The two hybrid RANS/LES results show the superior prediction of the mean velocity profiles around the pins, pressure distributions on the pin wall, and Nusselt number distributions. However, the transitional model, k-ω SSTLM, shows large discrepancies except in front of the pins where the flow is not fully developed. The vortical structures are well resolved by the two hybrid RANS/LES models. The SBES model is particularly adept at capturing the 3-D vortex structures after the pins. The effects of the blending function switching between RANS and LES mode of the two hybrid RANS/LES models are also investigated.
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Yang, Xiao Long, Kai Yao Hu, Tie Ping Lin, and Jia Yang. "Effect of Turbulence Model on Simulation of Trailing Vortex around Ahmed Body." Applied Mechanics and Materials 52-54 (March 2011): 1905–10. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1905.

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The Realizable k-ε Reynolds averaged Navior-Stokes (RANS) turbulence models and SST k-w detached eddy simulation (DES) models are investigated for simulation of external flow and trailing vortex around Ahmed body. The 3-D N-S equations are solved with central finite volume scheme and half-implicit SIMPLE method. The time average parameters of the DES results, such as the pressure, velocity field and drag coefficient Cd, are verified by comparing with RANS and experiment data. The vortex structures of vertical, horizontal plane and cross-section, along with the turbulent kinetic energy of tail vortex are studied in details. The results show that for time averaged parameters both models can get reasonable results, while for capturing the instant flow structure, DES shows advantage over RANS model.
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Lasher, William C., and Peter J. Richards. "Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer." Journal of Ship Research 51, no. 01 (2007): 22–38. http://dx.doi.org/10.5957/jsr.2007.51.1.22.

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Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.
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Chýlek, Radomír, Ladislav Šnajdárek, and Jiří Pospíšil. "Vortex Tube: A Comparison of Experimental and CFD Analysis Featuring Different RANS Models." MATEC Web of Conferences 168 (2018): 02012. http://dx.doi.org/10.1051/matecconf/201816802012.

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The Ranque–Hilsch vortex tube represents a device for both cooling and heating applications. It uses compressed gas as drive medium. The temperature separation is affected by fluid flow behaviour inside the tube. It has not been sufficiently examined in detail yet and has the potential for further investigation. The aim of this paper is to compare results of numerical simulations of the vortex tube with obtained experimental data. The numerical study was using computational fluid dynamics (CFD), namely computational code STAR-CCM+. For the numerical study, a three-dimensional geometry model, and various turbulence physics models were used. For the validation of carried out calculations, an experimental device of the vortex tube of identical geometrical and operating conditions was created and tested. The numerical simulation results have been obtained for five different turbulence models, namely Standard k-ε, Realizable k-ε, Standard k-ω, SST k-ω and Reynolds stress model (RSM), were compared with experimental results. The most important evaluation factor was the temperature field in the vortex tube. All named models of turbulence were able to predict the general flow behaviour in the vortex tube with satisfactory precision. Standard k-ε turbulence model predicted temperature distribution in the best accordance with the obtained experimental data.
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Beg, Md Nazmul Azim, Rita F. Carvalho, Simon Tait, et al. "A comparative study of manhole hydraulics using stereoscopic PIV and different RANS models." Water Science and Technology 2017, no. 1 (2018): 87–98. http://dx.doi.org/10.2166/wst.2018.089.

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Abstract Flows in manholes are complex and may include swirling and recirculation flow with significant turbulence and vorticity. However, how these complex 3D flow patterns could generate different energy losses and so affect flow quantity in the wider sewer network is unknown. In this work, 2D3C stereo Particle Image Velocimetry measurements are made in a surcharged scaled circular manhole. A computational fluid dynamics (CFD) model in OpenFOAM® with four different Reynolds Averaged Navier Stokes (RANS) turbulence model is constructed using a volume of fluid model, to represent flows in this manhole. Velocity profiles and pressure distributions from the models are compared with the experimental data in view of finding the best modelling approach. It was found among four different RANS models that the re-normalization group (RNG) k-ɛ and k-ω shear stress transport (SST) gave a better approximation for velocity and pressure.
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Azorakos, Georgios, Bjarke Eltard Larsen, and David R. Fuhrman. "NEW METHODS FOR STABILIZING RANS TURBULENCE MODELS WITH APPLICATION TO LARGE SCALE BREAKING WAVES." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 19. http://dx.doi.org/10.9753/icce.v36v.waves.19.

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Recently, Larsen and Fuhrman (2018) have shown that seemingly all commonly used (both k-omega and k-epsilon variants) two-equation RANS turbulence closure models are unconditionally unstable in the potential flow beneath surface waves, helping to explain the wide-spread over-production of turbulent kinetic energy in CFD simulations, relative to measurements. They devised and tested a new formally stabilized formulation of the widely used k-omega turbulence model, making use of a modified eddy viscosity. In the present work, three new formally-stable k-omega turbulence model formulations are derived and tested in CFD simulations involving the flow and dynamics beneath large-scale plunging breaking waves.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/T2fFRgq3I8E
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Wu, Cheng, Yi Ping Wang, and Xue Yang. "Evaluation of Various Turbulence Models in Predicting Airflow and Turbulence around a Generic Vehicle Model." Advanced Materials Research 989-994 (July 2014): 3468–72. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.3468.

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For vehicle external aerodynamic computation, the selection of the turbulence model is very important. In current research, ten RANS turbulence models were introduced to compute the time-averaged flow field around the Ahmed model with 25° backlight angle. In order to evaluate the feasibility of the turbulence model, the results were compared with the related published experimental data. The results showed that the two equations RANS turbulence models were more favorable to compute the vehicle external flow field, but parts of the two equations turbulence model just could predict the aerodynamic drag coefficient or lift coefficient effectively. However, the results further revealed that the realizable k-ε could obtain the more accurate drag coefficient and lift coefficient simultaneously, and simulate the complex separation flow in the wake.
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Zhang, Yuxin, Xiao-ping Wu, Ming-yan Lai, Guo-ping Zhou, and Jie Zhang. "Feasibility Study of Rans in Predicting Propeller Cavitation in Behind-Hull Conditions." Polish Maritime Research 27, no. 4 (2020): 26–35. http://dx.doi.org/10.2478/pomr-2020-0063.

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Abstract 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.
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Dissertations / Theses on the topic "RANS k- model"

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Kudla, Thomas Lucas. "Implementation and Validation of a Modified Non-Equilibrium Wilcox K Omega Turbulence Model in Subsonic and Transonic Flow Regimes." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1373481080.

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Hamberg, Micaela, and Signe Dahlin. "Numerical Study on Hydrodynamic Characteristics of Flood Discharge Tunnel in Zipingpu Water Conservancy Project : Using RANS equations and the VOF model." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387206.

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To avoid the large amount of damage that floods can cause, spillway tunnels are used to control water levels. To ensure the safety of water transportation through spillway tunnels, the behaviour of the water throughout the tunnel is important to know. Physical experiments are time consuming and expensive, hence CFD simulations are a profitable option for investigating the performance of the spillway tunnel. In this project, simulations of water flow in a spillway tunnel were executed. A three dimensional model of the spillway tunnel in Zipingpu Water Conservancy Project was created in the software ANSYS Gambit. A coarse, middle and fine mesh with both hexahedral- and tetrahedral elements were also created for the model in ANSYS Gambit. The meshes were imported to ANSYS Fluent where the simulations, and a convergence analysis were made. The water flow was set to be described by the Reynolds-Averaged Navier-Stokes model, using the pressure solver, k-epsilon model and the VOF model. Physical experiments had previously been performed, and the simulated results were compared to these, in an attempt to find the parameters to replicate the experimental results to the greatest extent possible. The inlet velocity of the tunnel was known and the inlet boundary was set as a velocity inlet. The ceiling of the tunnel was set as a pressure inlet, the floor and walls were set as wall, and the outlet was set as pressure outlet. The simulated results showed similar behavior as the experimental results, but all differed from the experimental results. The grid convergence index, estimating the results' dependency on the mesh was 6.044 %. The flow was analyzed, and where the flow had unfavorable characteristics, such as a high cavitation number, the geometry of the spillway was altered in ANSYS Gambit to investigate if an improved geometry for the spillway tunnel could be found. The water flow in the revised geometry was simulated in ANSYS Fluent, and results showing flow with lower cavitation numbers was found.
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Lorenc, Václav. "Analýza proudových poměrů v okolí nové vodní elektrárny." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372290.

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The diploma thesis deals with analysis of flow ratios at the hydraulic plant Klecany – Roztoky, located in the region of Střední Čechy at Vltava river (km 37,08). At this site 3D streaming of superficial water was simulated aiming to evaluate the influence of potencial construction of the new hydroelectric power plant Klecany II on existing Klecany I. Using all of the base documentation available, 3D models of current and planned conditions were created to serve as base for calculation in FLOW 3D. The first part of the thesis describes, how the planned construction of the new hydroelectric power plant Klecany II could influence the current fairway at the inlet 400 m3/s. The second part analyses shape of planned flow hydroelectric power plant Klecany II for flow Q90d, equal to 180 m3/s. All of the results are presented in intelligible charts and images.
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Šesták, Josef. "Analýza proudění spalin v okolí výfukového ventilu spalovacího motoru s využitím CFD." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228659.

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This diploma thesis discuss a flow in a vicinity of exhaust valve using computational of fluid dynamics. In a light of current state of the problem solution this approach is forward but very sophisticated. Intention of author is description of multidimensional boundary of characteristic variables which determinates the flow behaviour for given geometry and boundary conditions. Technical knowlegde of fluid flow in vicinity of exhaust valve allow to design geometry which provide more effective cylinder flush out berofe the exhaust stroke will become. This process reduce quantity of loss work of piston and improve its effective pointers.
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Fock, Björn Hendrik [Verfasser], and K. Heinke [Akademischer Betreuer] Schlünzen. "RANS versus LES models for investigations of the urban climate / Björn Hendrik Fock. Betreuer: K. Heinke Schlünzen." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2015. http://d-nb.info/1068316586/34.

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Agarwal, Amit Balkrishna. "FUNCTIONAL DIFFERENCES BETWEEN H-RAS AND K-RAS IN TRANSGENIC MOUSE TUMORS." VCU Scholars Compass, 2007. http://scholarscompass.vcu.edu/etd_retro/74.

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The ras genes, including Harvey ras (H-ras) and Kirsten ras (K-ras), were among the first oncogenes discovered, and are the most commonly mutated oncogenes in human cancer. The H-ras and K-ras proteins are 85% identical and share considerable functional overlap. However, there is increasing evidence for functional differences between the two proteins that may impart different properties to tumors arising from mutations in these two genes. To study the functional differences between H-ras and K-ras in an in vivo setting, we used two different transgenic mouse tumor models, MMTV-H-ras and MMTV-K-ras mice. The MMTV-H-ras mice were originally developed in Dr. Leder's lab and have been well characterized with regard to tumor properties. We created a similar line of transgenic mice expressing mutant K-ras (G12V) under the control of the MMTV promoter. Female mice of both lines develop primarily mammary tumors. We compared differences between the H-ras and K-ras lines with regard to age of tumor onset, rate of tumor growth, and rates of tumor proliferation and apoptosis. The tumors were also characterized by microarray analysis to look for genes that are differentially expressed in the two tumor types. Finally, the response of tumors to two common chemotherapeutic agents, doxorubicin and taxol, was also measured. We found that tumors in the MMTV-H-ras and MMTV-K-ras mice were similar with respect to several tumor properties, including age of onset, histopathology, and proliferation and apoptotic indices. While tumors from mice of these two genotypes clustered separately in an unsupervised analysis of gene expression profiles, the differentially expressed genes did not fall within any well-defined signaling pathways. However, drug studies indicated differences in response to doxorubicin between the two isoforms, with H-ras tumors responding better than K-ras tumors. In conclusion, our studies point to specific differences between H-ras and K-ras that may represent novel signaling pathways not currently known to be regulated by Ras. In spite of the few differences in properties of tumors arising from H-ras and K-ras mutation, there might be differences in response to chemotherapeutic agents that could have clinical significance.
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Li, Zhiyong. "Data-Driven Adaptive Reynolds-Averaged Navier-Stokes k - ω Models for Turbulent Flow-Field Simulations". UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/93.

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The data-driven adaptive algorithms are explored as a means of increasing the accuracy of Reynolds-averaged turbulence models. This dissertation presents two new data-driven adaptive computational models for simulating turbulent flow, where partial-but-incomplete measurement data is available. These models automatically adjust (i.e., adapts) the closure coefficients of the Reynolds-averaged Navier-Stokes (RANS) k-ω turbulence equations to improve agreement between the simulated flow and a set of prescribed measurement data. The first approach is the data-driven adaptive RANS k-ω (D-DARK) model. It is validated with three canonical flow geometries: pipe flow, the backward-facing step, and flow around an airfoil. For all 3 test cases, the D-DARK model improves agreement with experimental data in comparison to the results from a non-adaptive RANS k-ω model that uses standard values of the closure coefficients. The second approach is the Retrospective Cost Adaptation (RCA) k-ω model. The key enabling technology is that of retrospective cost adaptation, which was developed for real-time adaptive control technology, but is used in this work for data-driven model adaptation. The algorithm conducts an optimization, which seeks to minimize the surrogate performance, and by extension the real flow-field error. The advantage of the RCA approach over the D-DARK approach is that it is capable of adapting to unsteady measurements. The RCA-RANS k-ω model is verified with a statistically steady test case (pipe flow) as well as two unsteady test cases: vortex shedding from a surface-mounted cube and flow around a square cylinder. The RCA-RANS k-ω model effectively adapts to both averaged steady and unsteady measurement data.
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Sampath, Srinath. "Analysis of Agreement Between Two Long Ranked Lists." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385415346.

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Granell, Ruiz Rafael. "Análisis del flujo ambiental y propuesta metodológica para simulaciones CFD aplicadas a la ventilación natural de invernaderos." Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/37194.

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El cultivo protegido bajo invernadero tiene altos costes energéticos derivados de la ventilación forzada. En cambio, la ventilación natural puede ser una solución barata que reduzca el consumo energético. No obstante, un diseño que permita la ventilación natural del invernadero supone un reto debido a la complejidad del fenómeno físico. Frente a otros métodos de diseño, como los métodos experimentales o analíticos, en los últimos tiempos la dinámica de fluidos computacional (CFD por sus siglas en inglés) se ha convertido en la herramienta más utilizada para estudiar este tipo de fenómenos, gracias a su relativo bajo coste y a la rapidez en la obtención de resultados. No obstante, los modelos CFD deben refrendarse mediante validaciones realizadas a través de datos experimentales. Un análisis bibliográfico detallado del uso de la CFD aplicada a invernaderos muestra, en general, que los trabajos carecen de suficientes datos experimentales, seguramente debido al alto coste de los sensores para adquirirlos y la dificultad que conlleva el trabajo en condiciones de campo. Además, se observa que las simulaciones CFD en invernaderos no se realizan con un procedimiento sistematizado. Por ello, la presente tesis, por un lado describe un dispositivo y unos métodos sencillos y baratos para obtener datos atmosféricos, y por otro, propone una visión crítica sobre la investigación realizada hasta el momento, con el fin de sistematizar la manera de generar modelos CFD aplicados a la ventilación natural de invernaderos. Finalmente, la tesis se complementa con un ejemplo sobre un caso práctico. Para ello, en primer lugar, se realizó una revisión bibliográfica de las diferentes guías de buenas prácticas en diferentes campos de la tecnología principalmente en edificación, para sistematizar y adaptar las recomendaciones para generar modelos CFD en invernaderos. En segundo lugar, se desarrolló un sistema de adquisición de datos sencillo, consistente en una red de sensores, que permite medir simultáneamente la velocidad y dirección de viento en 20 puntos. Este sistema de sensores fue calibrado y probado en campo satisfactoriamente obteniendo una precisión similar a los anemómetros comerciales con un precio 30 veces superior. En tercer lugar, se generaron 24 modelos del flujo de aire alrededor del invernadero, resultantes de la combinación de cuatro modelos de turbulencia (k- ¿; RNG k-¿; k-¿ y RSM); dos esquemas de discretización (primer orden y segundo orden) y tres velocidades de viento exterior (3; 3,5 y 4 m/s) con el fin de analizar sus diferencias y demostrar sus ventajas e inconvenientes. Por este motivo, en cuarto lugar, se comprobó su capacidad de ajustarse a los datos de campo, validando los modelos con un análisis de regresión lineal sobre los datos experimentales. Con este estudió se reveló que los modelos SST k-¿ y el RSM (segundo orden) son los que mejor representan el flujo de ventilación y se demostró que el modelo k-¿ estándar (primer orden), el más utilizado en la bibliografía, no sólo ofrece resultados diferentes al resto de modelos, sino que su rendimiento es pobre para predecir el flujo de ventilación.<br>Granell Ruiz, R. (2014). Análisis del flujo ambiental y propuesta metodológica para simulaciones CFD aplicadas a la ventilación natural de invernaderos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37194<br>TESIS
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Bott, Simone [Verfasser], and K. [Akademischer Betreuer] Amann. "Effekte einer oralen Therapie mit S 18886, einem TP-Rezeptor-Antagonisten, auf kardiovaskuläre Strukturveränderungen im Hypertonie-Modell der doppelt transgenen "human renin-angiotensinogen rats" (dTGR) / Simone Bott. Betreuer: K. Amann." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2012. http://d-nb.info/1023597586/34.

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Book chapters on the topic "RANS k- model"

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Kubacki, S., and E. Dick. "Hybrid RANS/LES of Plane Impinging Jets with k-ω Based Models." In Progress in Hybrid RANS-LES Modelling. Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14168-3_22.

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Jurečková, Jana. "Regression rank scores in nonlinear models." In Beyond Parametrics in Interdisciplinary Research: Festschrift in Honor of Professor Pranab K. Sen. Institute of Mathematical Statistics, 2008. http://dx.doi.org/10.1214/193940307000000121.

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Caillet, Hélène, Alain Bastide, and Laetitia Adelard. "CFD Simulations in Mechanically Stirred Tank and Flow Field Analysis: Application to the Wastewater (Sugarcane Vinasse) Anaerobic Digestion." In Wastewater Treatment [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93926.

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Anaerobic digestion is a widely used process for waste treatment and energy production. This natural process takes place in a controlled environment, anaerobic digesters. Mixing is one of the main operating parameters. The understanding of the flows during the agitation of the medium is crucial for the optimization of the process yield. In fact, the mass and heat transfers are enhanced by the agitation. However, the complex biochemical reactions can be inhibited with overly vigorous agitation. A detailed and in-depth understanding of the phenomena occurring during agitation requires modeling studies. In this chapter, we propose a general approach, based on computational fluid mechanics (CFD), to analyze the mechanical mixing of an anaerobic reactor. We apply this work to the anaerobic digestion of the sugarcane vinasse, which is a liquid waste generated during the production of alcohol. The single-phase Reynolds-averaged Navier-Stokes (RANS) simulations of mechanical agitation of Newtonian fluids for different rotational speeds are presented. The equations system is closed with the standard k-epsilon turbulence model. The flow field is analyzed with the velocity profiles, the Q and Lambda2 fields, the pressure and the vorticity.
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Ali Mergheni, Mohamed, Mohamed Mahdi Belhajbrahim, Toufik Boushaki, and Jean-Charles Sautet. "A New Combustion Method in a Burner with Three Separate Jets." In Numerical and Experimental Studies on Combustion Engines and Vehicles. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.90571.

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Oxy-flames from burners with separated jets present attractive perspectives because the separation of reactants generates a better thermal efficiency and reduction of pollutant emissions. The principal idea is to confine the fuel jet by oxygen jets to favor the mixing in order to improve the flame stability. This chapter concerns the effect of equivalence ratio on characteristics of a non-premixed oxy-methane flame from a burner with separated jets. The burner of 25 kW power is composed with three aligned jets, one central methane jet surrounded by two oxygen jets. The numerical simulation is carried out using Reynolds Average Navier-Stokes (RANS) technique with k-ε as a turbulence closure model. The eddy dissipation model is applied to take into account the turbulence-reaction interactions. The study is performed with different global equivalence ratios (0.7, 0.8 and 1). The validation of the numerical tools is done by comparison with experimental data of the stoichiometric regime (Ф = 1). The two lean regimes of Ф = 0.7 and 0.8 are investigated only by calculations. The velocity fields with different equivalence ratio are presented. It yields to increase of longitudinal and transverse velocity, promotes the fluctuation in interaction zone between fuel and oxygen also a better mixing quality and a decrease of the size of the recirculation zone.
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Alkan, Ahmet Dursun, Onur Usta, Alpay Acar, and Elis Atasayan. "Investigation of Environmental Effects of High Speed Boats." In Progress in Marine Science and Technology. IOS Press, 2020. http://dx.doi.org/10.3233/pmst200021.

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Luxury high-speed boats are increasingly being used for entertainment purposes. However, not only humans, but also animals are negatively affected by high-speed boats, and time is running out fast for people to do something about it. This study presents a review of current negative effects of high-speed boats to the environment. In this study, the flow around a benchmark planing Fridsma boat is simulated by CFD and resistance values for different non-dimensional Froude number (Fn) conditions are validated from the experimental results obtained from the literature. Using the same CFD methodology, a catamaran model in which the towing tank test results are available, is simulated for different Fn conditions and resistance values are predicted. In the CFD analysis, unsteady flow around the Fridsma hull model and catamaran model is simulated using overset meshing technique and turbulence is modeled by Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-omega turbulence model. Resistance values are compared with the experimental data and required propulsion powers are estimated for different Fn conditions. Then, total resistance of the catamaran for full-scale vessel is calculated using an extrapolation method and required propulsion power predictions are conducted. Noise prediction, corresponding to the required propulsion power are presented. In particular, the change of noise level and harmful gases released into the environment, when the speed of the vessel increases are examined and discussed. Consequently, it is believed that this study would lay an important foundation for the widespread investigation for the negative effects of the high-speed boats in the future.
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De Padova, Diana, and Michele Mossa. "Hydrodynamics of Regular Breaking Wave." In Geophysics and Ocean Waves Studies [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94449.

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Turbulence and undertow currents play an important role in surf-zone mixing and transport processes; therefore, their study is fundamental for the understanding of nearshore dynamics and the related planning and management of coastal engineering activities. Pioneering studies qualitatively described the features of breakers in the outer region of the surf zone. More detailed information on the velocity field under spilling and plunging breakers can be found in experimental works, where single-point measurement techniques, such as Hot Wire Anemometry and Laser Doppler Anemometry (LDA), were used to provide maps of the flow field in a time-averaged or ensemble-averaged sense. Moreover, the advent of non-intrusive measuring techniques, such as Particle Image Velocimetry (PIV) provided accurate and detailed instantaneous spatial maps of the flow field. However, by correlating spatial gradients of the measured velocity components, the instantaneous vorticity maps could be deduced. Moreover, the difficulties of measuring velocity due to the existence of air bubbles entrained by the plunging jet have hindered many experimental studies on wave breaking encouraging the development of numerical model as useful tool to assisting in the interpretation and even the discovery of new phenomena. Therefore, the development of an WCSPH method using the RANS equations coupled with a two-equation k–ε model for turbulent stresses has been employed to study of the turbulence and vorticity distributions in in the breaking region observing that these two aspects greatly influence many coastal processes, such as undertow currents, sediment transport and action on maritime structures.
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"Case Study Analysis of a Resource Room and Self-Contained Classroom Model With Emotionally Disturbed Students." In Advances in Early Childhood and K-12 Education. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8069-0.ch008.

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The chapter focuses on the IDEA disability category of emotional disturbance (ED), which ranks fifth among school-aged students in the United States that have been diagnosed with an exceptionality. ED is a disability that, due to severe behavioral and mental health issues, affects a student's ability to succeed academically in school, which many times leads to the student not finishing high school. The chapter explains that most service delivery models for students who are classified as ED occur in a resource room or self-contained classroom model. Two case studies demonstrate services within such models that have been found to be successful. The chapter also includes a discussion on specific intervention strategies that can assist teachers working with ED students.
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Sahu, Sanat Kumar, and A. K. Shrivas. "Analysis and Comparison of Clustering Techniques for Chronic Kidney Disease With Genetic Algorithm." In Research Anthology on Multi-Industry Uses of Genetic Programming and Algorithms. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-8048-6.ch046.

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The purpose of this article is to weigh up the foremost imperative features of Chronic Kidney Disease (CKD). This study is based mostly on three cluster techniques like; K means, Fuzzy c-means and hierarchical clustering. The authors used evolutionary techniques like genetic algorithms (GA) to extend the performance of the clustering model. The performance of these three clusters: live parameter purity, entropy, and Adjusted Rand Index (ARI) have been contemplated. The best purity is obtained by the K-means clustering technique, 96.50%; whereas, Fuzzy C-means clustering received 93.50% and hierarchical clustering was the lowest at 92. 25%. After using evolutionary technique Genetic Algorithm as Feature selection technique, the best purity is obtained by hierarchical clustering, 97.50%, compared to K –means clustering, 96.75%, and Fuzzy C-means clustering at 94.00%.
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Chatterjee, Ahan, Swagatam Roy, and Rupali Shrivastava. "A Machine Learning Approach to Prevent Cancer." In Handbook of Research on Disease Prediction Through Data Analytics and Machine Learning. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-2742-9.ch007.

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One of the most talked about diseases of the 21st century is none other than cancer. In this chapter, the authors take a closer look to prevent cancer through machine learning approach. At first, they ran their classifier models (e.g., decision tree, K-mean, SVM, etc.) to check which algorithm gives the best result in terms of choosing right features for further treatment. The classified results are compared, and then various feature reduction algorithm is being used to identify exactly which features affects the most. Various data mining algorithms are being used, namely rough-based theory, graph-based clustering, to extract the most important features which influence the results. In the next section they take a look in the cancer analytics part. A simulation model has been designed that can easily manage the patient flow in OPDs and a bed rotation model also have been designed to give patients an insight that how much time they will spend in the queue. Further they analyzed a risk analysis model for chemotherapy treatment, and finally, an econometric discussion has been drawn in how it affects the treatment.
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Majhi, Babita, Sachin Singh Rajput, and Ritanjali Majhi. "Performance Evaluation of Machine Learning Techniques for Customer Churn Prediction in Telecommunication Sector." In Advances in Data Mining and Database Management. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-6659-6.ch015.

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The principle objective of this chapter is to build up a churn prediction model which helps telecom administrators to foresee clients who are no doubt liable to agitate. Many studies affirmed that AI innovation is profoundly effective to anticipate this circumstance as it is applied through training from past information. The prediction procedure is involved three primary stages: normalization of the data, then feature selection based on information gain, and finally, classification utilizing different AI methods, for example, back propagation neural network (BPNNM), naïve Bayesian, k-nearest neighborhood (KNN), support vector machine (SVM), discriminant analysis (DA), decision tree (DT), and extreme learning machine (ELM). It is shown from simulation study that out of these seven methods SVM with polynomial based kernel is coming about 91.33% of precision where ELM is at the primary situation with 92.10% of exactness and MLANN-based CCP model is at third rank with 90.4% of accuracy. Similar observation is noted for 10-fold cross validation also.
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Conference papers on the topic "RANS k- model"

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Rodebaugh, Gregory, Kevin Brinckman, and Sanford Dash. "DDES of Aeropropulsive Flows Based on an Extended k-? RANS Model." In 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-393.

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Hodson, Joshua D., Robert E. Spall, and Barton L. Smith. "RANS Predictions in an Idealized Lower-Plenum Model." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89222.

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The two-dimensional, unsteady, Reynolds-averaged Navier-Stokes equations have been solved for the flow across a row of confined cylinders with a pitch-to-diameter ratio of 1.7, a configuration which was designed to model a next generation nuclear plant lower-plenum. Four different turbulence models were used: k–ε, k–ω, v2–f, and differential Reynolds-stress transport. Comparisons with available experimental data were made for pressure losses, recirculation lengths, and mean velocity profiles. The results indicate that all models did a reasonable job of predicting the pressure loss coefficient. However, in terms of the mean velocities and recirculation length, the determination of which model performed best is not clear.
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Qun, Wei, Chen Hongxun, and Ma Zheng. "Numerical Simulation of Flow Around Airfoil With Non-Linear RANS Model." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-02777.

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The standard k-ε eddy viscosity model is the most commonly used model in computational fluid dynamics and perform well in application, but less effective for flows with high mean shear rate or massive separation. An non-linear eddy viscosity k-ε model was developed to compensate the deficit, in which the Cμ determined by an expression of shear strain rate rather than a constant on the base of experimental and DNS data. Two-dimensional CFD simulations were carried out by proposed NL k-ε model and standard k-ε model for wind-turbine airfoil S809 with the general purpose CFD code ANSYS CFX 12.1. Results show that standard k-ε can predict the flow around the airfoil for angles of attack with attached flow, but is not qualified for flow at angles of attack with strong flow separation, whereas non-linear k-ε model can improve the accuracy of the performance coefficients to some extent, and when large flow separation generates, non-linear k-ε model can improve the accuracy of pressure distribution around the airfoil and simulate the flow separation more correctly.
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Arvidson, Sebastian, Lars Davidson та Shia-Hui Peng. "Hybrid RANS-LES Modeling Using a Low-Reynolds-Number k-ω Based Model". У 52nd Aerospace Sciences Meeting. American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-0225.

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Yamamoto, Makoto. "Proposal of a RANS Model to Predict Both K- and D-Type Roughness." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45349.

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The effect of surface roughness on the aerodynamic performance of a blade and an airfoil is one of very important issues in aeronautic and mechanical engineering. Since existing turbulence models were developed for uniformly distributed roughness, the availability would be limited under a certain flow and roughness conditions. Considering a blade surface with ice accretion, foreign object damage and erosion, the roughness is not uniformly distributed, but isolated or local. Therefore, in such a multi-physics simulation, it is needed to develop a more universal turbulence model to predict the flow fields around a blade with various types of surface roughness. In the present study, employing the virtual force that represents the effect of each roughness element on the mean flow field, I develop and verify a new k–ε turbulence model that can be successfully applied to both k- and d-type roughness.
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Taylor, Benjamin H., Tausif Jamal, and D. Keith Walters. "Performance Evaluation of a Non-Linear Explicit Algebraic Reynolds Stress Model for Surface Mounted Obstacles." In ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20304.

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Abstract The presence of complex vortical structures, unsteady wakes, separated shear layers, and streamline curvature pose considerable challenges for traditional linear Eddy-Viscosity (LEV) models. Since Non-Linear Eddy Viscosity Models (NEV) models contain additional strain-rate and vorticity relationships, they can provide a better description for flows with Reynolds stress anisotropy and can be considered to be suitable alternatives to traditional EVMs in some cases. In this study, performance of a Non-Linear Explicit Algebraic Reynolds Stress Model (NEARSM) to accurately resolve flow over a surface mounted cube and a 3D axisymmetric hill is evaluated against existing experimental and numerical studies. Numerical simulations were performed using the SST k-ω RANS model, SST k-ω-NEARSM, SST-Multiscale LES model, and two variants of the Dynamic Hybrid RANS-LES (DHRL) model that include the SST k-ω and the SST k-ω-NEARSM as the RANS models. Results indicate that the SST k-ω RANS model fails to accurately predict the flowfield in the separated wake region and although the SST-NEARSM and SST-Multiscale LES models provide an improved description of the flow, they suffer from incorrect RANS-LES transition caused by Modeled Stress Depletion (MSD) and sensitivity to changes in grid resolution. The SST-DHRL and the SST-NEARSM-DHRL variants provide the best agreement to experimental and numerical data.
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Sajjadi, H., M. Salmanzadeh, G. Ahmadi, and S. Jafari. "Hybrid LES/RANS Model for Simulation of Particle Dispersion and Deposition." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83383.

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Particle dispersion and deposition in a modeled room was investigated using the Lattice Boltzmann method (LBM) in conjunction with the hybrid RANS/LES turbulence model. For this new model a combination of LES and RANS models was used to reduce the computational cost of using the full LES in the entire domain. Here the near wall region was simulated by the RANS model, while the rest of the domain was analyzed using the LES model within the framework of the LBM. The k-ε turbulence model was applied in the RANS region. For using the k-ε model in the LBM framework, two additional distribution functions for k and ε were defined. For the LES region the sub-grid scale turbulence effects were simulated through a Smagorinsky model. To study the particle dispersion and deposition in the modeled room, particles with different sizes (diameters of 10nm to 10 μm) were investigated. The simulated results for particle dispersion and deposition showed that the predictions of the present hybrid method were quite similar to the earlier LES-LBM. In addition, the predictions of the hybrid model for the particle deposition and dispersion were closer to the LES simulation results compared to those of the k-ε model. It was shown that the Brownian excitation is very important for nanoparticles and the number of deposited particles for 10nm particles is higher than those for the larger 100nm and 1μm particles. The deposition rate for 10 μm particles is also high due to the inertial effects.
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Eriksson, Pontus. "The Zimont TFC Model Applied to Premixed Bluff Body Stabilized Combustion Using Four Different RANS Turbulence Models." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27480.

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The Volvo Aero Corp. (VAC) Triangular Bluff Body Stabilized Combustion rig VR-1 has been extensively researched both in terms of experiments and theoretical treatment. Previous CFD work has concentrated on Reynolds Averaged Navier-Stokes (RANS) models combined with the Level Set Flamelet Library approach. Large Eddy Simulation (LES) has also been applied to the case. In this paper the Zimont Turbulent Flame Closure (TFC) model has been investigated in conjunction with the k-ε, k-ω, SST k-ω and RSM RANS model implementations in ANSYS CFX 10.0. It is shown that the various RANS models generate significantly different results in terms of turbulent velocity and integral length scale fields. These parameters influence the computed turbulent flame speed. The turbulent viscosity fields also differ substantially between the various RANS models. This will affect the computed degree of flame front diffusion. For the investigated case; the TFC model combined with the k-ω model fairly accurately captures the recirculation zone length and overall turbulent flame speed. The measured case however displays Kelvin-Helmholtz induced oscillations of the shear layers behind the bluff body. This will combine with the free-stream turbulence and turbulence generated along the upstream surfaces of the bluff body to distort the flame sheets. The two flame fronts will also be subjected to other (unquantified) combustion related instabilities. The combined effect is not captured well in steady state RANS. The analysis is therefore seen to grossly under-predict flame front diffusion, regardless of turbulence model.
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Oriji, Ugochukwu R., and Paul G. Tucker. "RANS Modelling of Accelerating Boundary Layers." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63467.

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A numerical investigation of accelerated boundary layers (BL) has been performed using linear and non-linear eddy viscosity models (EVM). The acceleration parameters (KS) investigated range between 1.5×10−6 and 3.0×10−6. The one equation (k-l), Spalart Allmaras (SA) and the two-equation Menter SST and Chien models in their standard forms are found to be insensitive to acceleration. Nevertheless, proposed modifications for the SA, Chien and the k-l models significantly improved predictions. The major improvement was achieved by modifying the damping functions in these models and also an analogous source term, E, for the Chien model. Encouraging agreement with measurements is found using the Launder Sharma (LS), Cubic and Explicit Algebraic Stress Models (EASM) in their standard forms. The cubic model best predicted the turbulence quantities. Investigations confirm that it is practical for Reynolds Average Navier-Stokes (RANS) models to capture reversion from the turbulent to laminar state albeit for equilibrium sink type flows.
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Sajjadi, H., M. Salmanzadeh, G. Ahmadi, and S. Jafari. "Lattice Boltzmann Method Simulation of Turbulent Indoor Airflow Using Hybrid LES/RANS Model." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69120.

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In this study the hybrid RANS/LES turbulence model within the framework of the Lattice Boltzmann method (LBM) was used to study turbulent indoor airflows. In this approach the near wall region was simulated by the RANS model, while the bulk of the domain was analyzed using the LES model with the LBM approach. In the near wall layer where RANS was used, the k-ε turbulence model was employed. For the k-ε turbulence model in conjunction with the LBM two population balance equations for k and ε were used. The present simulation results for the airflow showed good agreement with the experimental data and the earlier numerical results for the hybrid RANS/LES. The results showed that the hybrid model properly predicted the large scale turbulence fluctuation velocities in the bulk of the flow region. In addition, the computational time for the hybrid model is less than that of the LES method.
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Reports on the topic "RANS k- model"

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Lefantzi, Sophia, Jaideep Ray, Srinivasan Arunajatesan, and Lawrence DeChant. Tuning a RANS k-e model for jet-in-crossflow simulations. Office of Scientific and Technical Information (OSTI), 2013. http://dx.doi.org/10.2172/1096265.

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Greenough, J., and M. Wickett. Simulations of the Tilted Rocket Rig Experiment using the K-L RANS Model in the Ares Hydrodynamics Code. Office of Scientific and Technical Information (OSTI), 2012. http://dx.doi.org/10.2172/1057710.

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