Download or read book Advanced Turbulence Modeling Strategies Within the Hybrid RANS LES Framework written by Tausif Jamal and published by . This book was released on 2020 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Hybrid RANS LES Modelling written by Yannick Hoarau and published by Springer Nature. This book was released on 2019-11-01 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the Seventh Symposium on Hybrid RANS-LES Methods, which was held on September 17-19 in Berlin, Germany. The different chapters, written by leading experts, reports on the most recent developments in flow physics modelling, and gives a special emphasis to industrially relevant applications of hybrid RANS-LES methods and other turbulence-resolving modelling approaches. The book addresses academic researchers, graduate students, industrial engineers, as well as industrial R&D managers and consultants dealing with turbulence modelling, simulation and measurement, and with multidisciplinary applications of computational fluid dynamics (CFD), such as flow control, aero-acoustics, aero-elasticity and CFD-based multidisciplinary optimization. It discusses in particular advanced hybrid RANS-LES methods. Further topics include wall-modelled Large Eddy Simulation (WMLES) methods, embedded LES, Lattice-Bolzman methods and turbulence-resolving applications and a comparison of the LES methods with both hybrid RANS-LES and URANS methods. Overall, the book provides readers with a snapshot on the state-of-the-art in CFD and turbulence modelling, with a special focus to hybrid RANS-LES methods and their industrial applications.

Download or read book Multiscale And Multiresolution Approaches In Turbulence Les Des And Hybrid Rans les Methods Applications And Guidelines 2nd Edition written by Pierre Sagaut and published by World Scientific. This book was released on 2013-03-25 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book aims to provide the reader with an updated general presentation of multiscale/multiresolution approaches in turbulent flow simulations. All modern approaches (LES, hybrid RANS/LES, DES, SAS) are discussed and recast in a global comprehensive framework. Both theoretical features and practical implementation details are addressed. Some full scale applications are described, to provide the reader with relevant guidelines to facilitate a future use of these methods./a

Download or read book Development of an Advanced Hybrid U RANS LES Turbulence Models Using Scale Adaptive Simulation SAS Method written by Rohit Saini and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Hybrid RANS LES Modelling written by Shia-Hui Peng and published by Springer Science & Business Media. This book was released on 2008-01-24 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence modelling has long been, and will remain, one of the most important t- ics in turbulence research, challenging scientists and engineers in the academic world and in the industrial society. Over the past decade, Detached Eddy Simulation (DES) and other hybrid RANS-LES methods have received increasing attention from the turbulence-research community, as well as from industrial CFD engineers. Indeed, as an engineering modelling approach, hybrid RANS-LES methods have acquired a remarkable profile in modelling turbulent flows of industrial interest in relation to, for example, transportation, energy production and the environment. The advantage exploited with hybrid RANS-LES modelling approaches, being - tentially more computationally efficient than LES and more accurate than (unsteady) RANS, has motivated numerous research and development activities. These activities, together with industrial applications, have been further facilitated over the recent years by the rapid development of modern computing resources. As a European initiative, the EU project DESider (Detached Eddy Simulation for Industrial Aerodynamics, 2004-2007), has been one of the earliest and most systematic international R&D effort with its focus on development, improvement and applications of a variety of existing and new hybrid RANS-LES modelling approaches, as well as on related numerical issues. In association with the DESider project, two subsequent international symposia on hybrid RANS-LES methods have been arranged in Stockholm (Sweden, 2005) and in Corfu (Greece, 2007), respectively. The present book is a result of the Second Symposium on Hybrid RANS-LES Methods, held in Corfu, Greece, 17-18 June 2007.

Download or read book A Dynamic Hybrid RANS LES Modeling Methodology for Turbulent transitional Flow Field Prediction written by Mohammad Faridul Alam and published by . This book was released on 2013 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: A dynamic hybrid Reynolds-averaged Navier-Stokes (RANS)-Large Eddy Simulation (LES) modeling framework has been investigated and further developed to improve the Computational Fluid Dynamics (CFD) prediction of turbulent flow features along with laminar-to-turbulent transitional phenomena. In recent years, the use of hybrid RANS/LES (HRL) models has become more common in CFD simulations, since HRL models offer more accuracy than RANS in regions of flow separation at a reduced cost relative to LES in attached boundary layers. The first part of this research includes evaluation and validation of a dynamic HRL (DHRL) model that aims to address issues regarding the RANS-to-LES zonal transition and explicit grid dependence, both of which are inherent to most current HRL models. Simulations of two test cases—flow over a backward facing step and flow over a wing with leading-edge ice accretion—were performed to assess the potential of the DHRL model for predicting turbulent features involved in mainly unsteady separated flow. The DHRL simulation results are compared with experimental data, along with the computational results for other HRL and RANS models. In summary, these comparisons demonstrate that the DHRL framework does address many of the weaknesses inherent in most current HRL models. Although HRL models are widely used in turbulent flow simulations, they have limitations for transitional flow predictions. Most HRL models include a fully turbulent RANS component for attached boundary layer regions. The small number of HRL models that do include transition-sensitive RANS models have issues related to the RANS model itself and to the zonal transition between RANS and LES. In order to address those issues, a new transition-sensitive HRL modeling methodology has been developed that includes the DHRL methodology and a physics-based transition-sensitive RANS model. The feasibility of the transition-sensitive dynamic HRL (TDHRL) model has been investigated by performing numerical simulations of the flows over a circular cylinder and a PAK-B airfoil. Comparisons with experimental data along with computational results from other HRL and RANS models illustrate the potential of TDHRL model for accurately capturing the physics of complex transitional flow phenomena.

Download or read book Progress in Hybrid RANS LES Modelling written by Sharath Girimaji and published by Springer. This book was released on 2015-02-20 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the Fifth Symposium on Hybrid RANS-LES Methods, which was held on March 19-21 in College Station, Texas, USA. The different chapters, written by leading experts, reports on the most recent developments in flow physics modelling, and gives a special emphasis to industrially relevant applications of hybrid RANS-LES methods and other turbulence-resolving modelling approaches. The book addresses academic researchers, graduate students, industrial engineers, as well as industrial R&D managers and consultants dealing with turbulence modelling, simulation and measurement, and with multidisciplinary applications of computational fluid dynamics (CFD), such as flow control, aero-acoustics, aero-elasticity and CFD-based multidisciplinary optimization. It discusses in particular advanced hybrid RANS-LES methods. Further topics include wall-modelled Large Eddy Simulation (WMLES) methods, embedded LES, and a comparison of the LES methods with both hybrid RANS-LES and URANS methods. Overall, the book provides readers with a snapshot on the state-of-the-art in CFD and turbulence modelling, with a special focus to hybrid RANS-LES methods and their industrial applications.

Download or read book Critical Assessment of Hybrid RANS LES Modeling for Attached and Separated Flows written by Mohammad Faridul Alam and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this study is to evaluate a recently proposed dynamic hybrid Reynolds-averaged Navier-Stokes (RANS)-Large Eddy Simulation (LES) modeling framework that seeks to effectively address issues regarding RANS-to-LES transition and explicit grid dependence inherent in most current hybrid RANS-LES (HRL) models. RANS-to-LES transition in the investigated dynamic HRL (DHRL) model is based on the physical concept of maintaining continuity of total turbulence production using two rigorously separated turbulent stress parameters, where one is obtained from the RANS model and the other from the LES model. Computations of two canonical test cases-two-dimensional turbulent channel flow and backward facing step flow-were performed to assess the potential of the DHRL model for predicting both attached and separated turbulent flows. This investigation attempts to evaluate the ability of the DHRL method to reproduce the detailed physics of attached and separated turbulent flows, as well as to resolve the issues concerning log-layer mismatch and delayed break down of separated shear layers. The DHRL model simulation results are compared with experimental and DNS data, along with the computational results for other HRL and RANS models. In summary, these comparisons demonstrate that the DHRL framework does address many of the weaknesses inherent in most current HRL models.

Download or read book Progress in Hybrid RANS LES Modelling written by Song Fu and published by Springer Science & Business Media. This book was released on 2012-08-14 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present book contains contributions presented at the Fourth Symposium on Hybrid RANS-LES Methods, held in Beijing, China, 28-30 September 2011, being a continuation of symposia taking place in Stockholm (Sweden, 2005), in Corfu (Greece, 2007), and Gdansk (Poland, 2009). The contributions to the last two symposia were published as NNFM, Vol. 97 and Vol. 111. At the Beijing symposium, along with seven invited keynotes, another 46 papers (plus 5 posters) were presented addressing topics on Novel turbulence-resolving simulation and modelling, Improved hybrid RANS-LES methods, Comparative studies of difference modelling methods, Modelling-related numerical issues and Industrial applications.. The present book reflects recent activities and new progress made in the development and applications of hybrid RANS-LES methods in general.

Download or read book Investigation of Novel Turbulence Modeling Techniques for Gas Turbines and Aerospace Applications written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Standard eddy-viscosity models lack curvature and system rotation sensitized terms in their formulation. Hence they fail to capture the effects of curvature and system rotation on turbulence anisotropy. As part of this effort, an algebraic expression for a characteristic rotation term is developed and tuned with the help of rotating homogeneous shear flow. This formulation is primarily based upon the rotation and curvature sensitized eddy-viscosity coefficient developed by York et al. (2009). A new scalar transport equation loosely based on Durbin's wall normal turbulent velocity scale (Durbin, 1991) is introduced to account for the modification in turbulence structure due to system rotation and curvature effects. The added transport equation also introduces history effects and stability in the solution with small increase in computational cost. The eddy-viscosity is redefined based on new turbulent velocity scale and hence the effects of rotation and streamline curvature are introduced into the mean momentum equation. A number of canonical test cases with significant curvature and rotation effects along with a cyclone flow, a representative of complex industrial flows, are considered for model validation. Hybrid modeling framework combines the strength of RANS in boundary layers and LES in separated shear layers to alleviate the weaknesses of RANS and limitations of LES model in some complex flows. A recently proposed hybrid RANS-LES modeling framework uses a weighing parameter that dynamically determines the RANS and LES regions based on solution statistics. The hybrid modeling methodology is implemented on a normal jet in crossflow, and a film cooling case for the purpose of model validation and evaluation. The final goal of the proposed effort is to combine advanced RANS modeling capability with LES using the new hybrid modeling framework. Specifically, the curvature and rotation sensitive RANS model developed here is coupled with commonly used LES models to produce a novel model for complex turbulent flows with the potential to improve accuracy of CFD predictions ((ersus existing RANS models) as well as significantly reduce the computational expense (versus existing LES models). Performance of the model form hence developed is evaluated on a cyclone flow case.

Download or read book Application of Hybrid RANS LES Turbulence Models written by R. H. Nichols and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Modelling Approaches written by Konstantin Volkov and published by BoD – Books on Demand. This book was released on 2017-07-26 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate prediction of turbulent flows remains a challenging task despite considerable work in this area and the acceptance of CFD as a design tool. The quality of the CFD calculations of the flows in engineering applications strongly depends on the proper prediction of turbulence phenomena. Investigations of flow instability, heat transfer, skin friction, secondary flows, flow separation, and reattachment effects demand a reliable modelling and simulation of the turbulence, reliable methods, accurate programming, and robust working practices. The current scientific status of simulation of turbulent flows as well as some advances in computational techniques and practical applications of turbulence research is reviewed and considered in the book.

Download or read book A New Approach for Turbulent Simulations in Complex Geometries written by and published by . This book was released on 2005 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Historically turbulence modeling has been sharply divided into Reynolds averaged Navier-Stokes (RANS), in which all the turbulent scales of motion are modeled, and large-eddy simulation (LES), in which only a portion of the turbulent spectrum is modeled. In recent years there have been numerous attempts to couple these two approaches either by patching RANS and LES calculations together (zonal methods) or by blending the two sets of equations. In order to create a proper bridging model, that is, a single set of equations which captures both RANS and LES like behavior, it is necessary to place both RANS and LES in a more general framework. The goal of the current work is threefold: to provide such a framework, to demonstrate how the Flow Simulation Methodology (FSM) fits into this framework, and to evaluate the strengths and weaknesses of the current version of the FSM. To do this, first a set of filtered Navier-Stokes (FNS) equations are introduced in terms of an arbitrary generalized filter. Additional exact equations are given for the second order moments and the generalized subfilted dissipation rate tensor. This is followed by a discussion of the role of implicit and explicit filters in turbulence modeling. The FSM is then described with particular attention to its role as a bridging model. In order to evaluate the method a specific implementation of the FSM approach is proposed. Simulations are presented using this model for the case of separating flow over a"hump" with and without flow control. Careful attention is paid to error estimation, and, in particular, how using flow statistics and time series affects the error analysis. Both mean flow and Reynolds stress profiles are presented, as well as the phase averaged turbulent structures and wall pressure spectra. Using the phase averaged data it is possible to examine how the FSM partitions the energy between the coherent resolved scale motions, the random resolved scale fluctuations, and the subfilter quantities. The method proves to be qualitatively successful at reproducing large turbulent structures. However, like other hybrid methods, it has difficulty in the region where the model behavior transitions from RANS to LES> Consequently the phase averaged structures reproduce the experiments quite well, and the forcing does significantly reduce the length of the separated region. Nevertheless, the recirculation length is signficantly too large for all cases. Overall the current results demonstrate the promise of bridging models in general and the FSM in particular. However, current bridging techniques are still in their infancy. There is still important progress to be made and it is hoped that this work points out the more important avenues for exploration.

Download or read book Anisotropic Hybrid Turbulence Modeling with Specific Application to the Simulation of Pulse actuated Dynamic Stall Control written by Sigfried William Haering and published by . This book was released on 2015 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies have shown pulse actuated dynamic stall control may provide a simple means to significantly increase the performance of lifting surfaces and expand their flight envelope. However, precise information of the complex boundary layer reattachment mechanisms are inaccessible to experimental measurements. Therefore, simulations are necessary to fully understand, optimize, and apply this method. Due to the inherent shortcomings of RANS, computational expense of LES, and deficiencies in current hybrid modeling approaches, a new hybrid modeling framework has been developed. Based in using the two-point second-order structure function to drive a local equilibrium between resolved and modeled turbulence, the new approach addresses issues associated with inhomogeneous and anisotropic grids as well as the treatment of the RANS/LES interface in hybrid simulations. Numerical studies using hybrid RANS/LES modeling approaches of a stalled airfoil with spanwise-uniform actuation regions experiencing single pulse actuated flow reattachment have been performed. The mechanism responsible for reattachment has been identified as a repeating wall-vortex interaction process. The new hybrid framework and anisotropic SGS models developed here are anticipated to be of great benefit well beyond the focus of this work with application to many challenging flow situations of pressing engineering interest.

Download or read book Machine Learning Methods for Modeling Turbulence in Large Eddy Simulations written by Marius Kurz and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reliable prediction of turbulent flows is of crucial importance since turbulence is prevalent in the majority of flows found in science and engineering. Turbulence is a multi-scale phenomenon, for which flow features can span several orders of magnitude in size. This results in enormous resolution requirements in numerical simulations of turbulent flow. The framework of large eddy simulation relaxes these resolution demands by resolving only the largest, most energetic features of the flow and approximating the dynamics of the smaller, unresolved scales with turbulence models. The goal of this thesis is to leverage the recent advances in machine learning methods to formulate data-driven modeling strategies for implicitly filtered large eddy simulation. To this end, two modeling strategies are devised based on the supervised and the reinforcement learning paradigms. First, artificial neural networks are trained using supervised learning to recover the unknown closure terms from the filtered flow field. It is demonstrated that recurrent neural networks can predict the unknown closure terms with excellent accuracy. The second modeling strategy is based on the reinforcement learning paradigm. For this, Relexi is introduced as a novel reinforcement learning framework that allows to employ legacy flow solvers as training environments at scale. With Relexi, artificial neural networks are trained within forced homogeneous isotropic turbulence to adapt the parameters of traditional turbulence models dynamically in space and time. The trained models provide accurate and stable simulations and generalize well to other resolutions and higher Reynolds numbers. It is demonstrated within this thesis that machine learning methods can be applied to derive data-driven turbulence models for implicitly filtered large eddy simulation and that these models can be trained and incorporated efficiently into practical simulations on high-performance computing systems.

Download or read book Predictive Capabilities of Advanced Turbulence Models in the Wake Region of a Wall Mounted Cube written by Benjamin Hugh Taylor and published by . This book was released on 2016 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis seeks to investigate the predictive capabilities of Advanced turbulence models in the wake region of a wall-mounted cube. Dynamic Hybrid RANS/LES (DHRL), Hybrid RANS/LES (HRL) models, Nonlinear Explicit Algebraic Reynolds Stress Model (NEARSM), One- and Two-equation models, and numerical flux schemes will be compared against Direct Numerical Simulation (DNS) results to determine which model, or combination of models, produce the closest replication. The simulations were ran in LociChem using both built-in features and modular code additions. The simulation results show the Shear Stress Transport (SST) model ran with NEARSM and Optimized Gradient REconstruction (OGRE) scheme gives better results than all other RANS and HRL models investigated herein. This result is matched only by SST with DHRL and OGRE. The best results were achieved using SST with NEARSM, DHRL, and OGRE. Thus, the NEARSM model shows potential to improve simulation results compared to simpler linear eddy-viscosity models.

Download or read book Full Committee Hearing on SBIR written by United States. Congress. House. Committee on Small Business and published by . This book was released on 2008 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: