Download or read book Hybrid RANS LES Modeling of High Re Turbulent Flows written by Bharanidharan Rajamani and published by . This book was released on 2008 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Progress in Hybrid RANS LES Modelling written by Yannick Hoarau and published by Springer. This book was released on 2018-03-09 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reports on the latest developments in computational fluid dynamics and turbulence modeling, with a special emphasis on hybrid RANS-LES methods and their industrial applications. It gathers the proceedings of the Sixth Symposium on Hybrid RANS-LES Methods, held on September 26-28 in Strasbourg, France. The different chapters covers a wealth of topics such as flow control, aero-acoustics, aero-elasticity and CFD-based multidisciplinary optimization. Further topics include wall-modelled Large Eddy Simulation (WMLES), embedded LES, Lattice-Bolzman methods, turbulence-resolving applications and comparisons between LES, hybrid RANS-LES and URANS methods. 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.

Download or read book Progress in Hybrid RANS LES Modelling written by Yannick Hoarau and published by Springer. This book was released on 2019-11-02 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 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 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 Direct and Large Eddy Simulation XI written by Maria Vittoria Salvetti and published by Springer. This book was released on 2019-02-02 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 11th workshop on Direct and Large Eddy Simulation (DLES), which was held in Pisa, Italy in May 2017. The event focused on modern techniques for simulating turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structures, as Direct Numerical Simulation (DNS), Large-Eddy Simulation (LES) or hybrid models based on a combination of LES and RANS approaches. In light of the growing capacities of modern computers, these approaches have been gaining more and more interest over the years and will undoubtedly be developed and applied further. The workshop offered a unique opportunity to establish a state-of-the-art of DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows and to discuss about recent advances and applications. This volume contains most of the contributed papers, which were submitted and further reviewed for publication. They cover advances in computational techniques, SGS modeling, boundary conditions, post-processing and data analysis, and applications in several fields, namely multiphase and reactive flows, convection and heat transfer, compressible flows, aerodynamics of airfoils and wings, bluff-body and separated flows, internal flows and wall turbulence and other complex flows.

Download or read book A Hybrid Numerical Simulation Approach for Turbulent Flows Over Building like Obstacles written by Kun-Jung Hsieh and published by . This book was released on 2008 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational fluid dynamics (CFD) has been widely applied to simulate turbulent flows in an urban environment. The two basic methodologies in CFD that have been applied here are a Reynolds-averaged Navier-Stokes (RANS) modeling and a large-eddy simulation (LES). The nature of the flow in a built-up urban area consisting of an arbitrary aggregation of buildings is dominated by unsteady large-scale turbulent structures. Recognizing that RANS is unable to correctly capture these turbulent structures while LES is associated with high computational costs, a hybrid RANS/LES methodology that combines the computational efficiency of RANS with the predictive accuracy of LES can be a promising simulation approach for the application to urban flows. In the non-zonal approach of hybrid RANS/LES methodology, a single generalized turbulence model is used in the entire computational domain. This model can function as a RANS turbulence closure model or as a LES subgrid scale model, depending on the local grid resolution or flow properties. A variant of non-zonal approaches, referred as partially resolved numerical simulation (PRNS) in this study, obtains the generalized turbulence model from the rescaling of a conventional RANS model through the incorporation of a resolution control function (F_R). The resolution control function F_R is used to characterize the degree of modeling required to represent the unresolved scales of motion. A new generalized functional form for F_R in PRNS is proposed in this thesis. The predictive performance of PRNS is compared with unsteady RANS (URANS) and LES computations, for a plane channel flow, and for fully-developed and developing flows over a matrix of cubes resembling a group of buildings. It is demonstrated that PRNS behaves similarly to LES, in terms of the predictions of the mean flow and turbulence, but outperforms URANS in general. This indicates PRNS is a promising approach for the simulation of complex turbulent flows in an urban environment.

Download or read book Multiscale and Multiresolution Approaches in Turbulence written by Pierre Sagaut and published by World Scientific. This book was released on 2013 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.

Download or read book Multiscale And Multiresolution Approaches In Turbulence written by Pierre Sagaut and published by World Scientific. This book was released on 2006-06-19 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book gives a general unified presentation of the use of the multiscale/multiresolution approaches in the field of turbulence. The coverage ranges from statistical models developed for engineering purposes to multiresolution algorithms for the direct computation of turbulence. It provides the only available up-to-date reviews dealing with the latest and most advanced turbulence models (including LES, VLES, hybrid RANS/LES, DES) and numerical strategies.The book aims at providing the reader with a comprehensive description of modern strategies for turbulent flow simulation, ranging from turbulence modeling to the most advanced multilevel numerical methods./a

Download or read book Hybrid Methodologies for Multiscale Separated Turbulent Flow Simulations written by and published by . This book was released on 2006 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract The goal of the present research is to develop and assess multiscale and hybrid turbulence models in simulation of separated turbulent flows at high Reynolds numbers in terms of grid refinement and CPU resources required for a certain level of spectral resolution of the separated flow. These investigated multiscale turbulence models include the DES (Detached Eddy Simulation), hybrid RANS (Reynolds-Averaged Navier Stokes) /LES (Large Eddy Simulation) and PANS (Partially Averaged Navier-Stokes) closure models. These techniques adapt a turbulence model, that function as a RANS model in regions where the grids are highly stretched and the high Reynolds number boundary layer is attached, to function as a sub-grid scale LES type model where the grid is nearly isotropic in the separated flow regions. This accomplished by reducing the turbulence eddy viscosity to promote resolution of more turbulence scales in these regions while still reverting to the original RANS behavior in attached flow and near wall regions. The sensitivity of the computed results to multiscale closure model parameters are compared for three developed formulations of the DES model, one variant of hybrid RANS/LES model, a proposed adaptation of the PANS model and the original multiscale SST-DES model for a number of problems involving unsteady separated high Reynolds number flow. The flow configurations include transonic flow over open cavity, subsonic flow over a back facing step and flow over wall-mounted hump. Simulation predictions are compared with experimental data and also equivalent LES simulations. Simulated results show that these models perform better when there is a distinct demarcation between the attached and separated regions and unsteady shear layers dominate the flow. Computed results show that multiscale methods based on the modification of the turbulent kinetic energy dissipation rate provide the most accurate results and the computed results for the unsteady spectra amplitude and frequency are significantly influenced by the model parameters and the grids. These models provide a useful tool for predicting complex 3-D separated unsteady flows over an expansive dynamic range at high Reynolds number and are comparable to LES predictions at (1/6)th - (1/10)th the corresponding LES CPU resources.

Download or read book DESider A European Effort on Hybrid RANS LES Modelling written by Werner Haase and published by Springer Science & Business Media. This book was released on 2009-05-12 with total page 469 pages. Available in PDF, EPUB and Kindle. Book excerpt: Preface “In aircraft design, efficiency is determined by the ability to accurately and rel- bly predict the occurrence of, and to model the development of, turbulent flows. Hence, the main objective in industrial computational fluid dynamics (CFD) is to increase the capabilities for an improved predictive accuracy for both complex flows and complex geometries”. This text part taken from Haase et al (2006), - scribing the results of the DESider predecessor project “FLOMANIA” is still - and will be in future valid. With an ever-increasing demand for faster, more reliable and cleaner aircraft, flight envelopes are necessarily shifted into areas of the flow regimes exhibiting highly unsteady and, for military aircraft, unstable flow behaviour. This undou- edly poses major new challenges in CFD; generally stated as an increased pred- tive accuracy whist retaining “affordable” computation times. Together with highly resolved meshes employing millions of nodes, numerical methods must have the inherent capability to predict unsteady flows. Although at present, (U)RANS methods are likely to remain as the workhorses in industry, the DESider project focussed on the development and combination of these approaches with LES methods in order to “bridge” the gap between the much more expensive (due to high Reynolds numbers in flight), but more accurate (full) LES.

Download or read book Computational Fluid Dynamics Modeling of Laminar Transitional and Turbulent Flows with Sensitivity to Streamline Curvature and Rotational Effects written by Varun Chitta and published by . This book was released on 2016 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling of complex flows involving the combined effects of flow transition and streamline curvature using two advanced turbulence models, one in the Reynoldsaveraged Navier-Stokes (RANS) category and the other in the hybrid RANS-Large eddy simulation (LES) category is considered in this research effort. In the first part of the research, a new scalar eddy-viscosity model (EVM) is proposed, designed to exhibit physically correct responses to flow transition, streamline curvature, and system rotation effects. The four equation model developed herein is a curvature-sensitized version of a commercially available three-equation transition-sensitive model. The physical effects of rotation and curvature (RC) enter the model through the added transport equation, analogous to a transverse turbulent velocity scale. The eddy-viscosity has been redefined such that the proposed model is constrained to reduce to the original transition-sensitive model definition in nonrotating flows or in regions with negligible RC effects. In the second part of the research, the developed four-equation model is combined with a LES technique using a new hybrid modeling framework, dynamic hybrid RANS-LES. The new framework is highly generalized, allowing coupling of any desired LES model with any given RANS model and addresses several deficiencies inherent in most current hybrid models. In the present research effort, the DHRL model comprises of the proposed four-equation model for RANS component and the MILES scheme for LES component. Both the models were implemented into a commercial computational fluid dynamics (CFD) solver and tested on a number of engineering and generic flow problems. Results from both the RANS and hybrid models show successful resolution of the combined effects of transition and curvature with reasonable engineering accuracy, and for only a small increase in computational cost. In addition, results from the hybrid model indicate significant levels of turbulent fluctuations in the flowfield, improved accuracy compared to RANS models predictions, and are obtained at a significant reduction of computational cost compared to full LES models. The results suggest that the advanced turbulence modeling techniques presented in this research effort have potential as practical tools for solving low/high Re flows over blunt/curved bodies for the prediction of transition and RC effects.

Download or read book Modeling Complex Turbulent Flows written by Manuel D. Salas and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence modeling both addresses a fundamental problem in physics, 'the last great unsolved problem of classical physics,' and has far-reaching importance in the solution of difficult practical problems from aeronautical engineering to dynamic meteorology. However, the growth of supercom puter facilities has recently caused an apparent shift in the focus of tur bulence research from modeling to direct numerical simulation (DNS) and large eddy simulation (LES). This shift in emphasis comes at a time when claims are being made in the world around us that scientific analysis itself will shortly be transformed or replaced by a more powerful 'paradigm' based on massive computations and sophisticated visualization. Although this viewpoint has not lacked ar ticulate and influential advocates, these claims can at best only be judged premature. After all, as one computational researcher lamented, 'the com puter only does what I tell it to do, and not what I want it to do. ' In turbulence research, the initial speculation that computational meth ods would replace not only model-based computations but even experimen tal measurements, have not come close to fulfillment. It is becoming clear that computational methods and model development are equal partners in turbulence research: DNS and LES remain valuable tools for suggesting and validating models, while turbulence models continue to be the preferred tool for practical computations. We believed that a symposium which would reaffirm the practical and scientific importance of turbulence modeling was both necessary and timely.

Download or read book Hybrid Turbulence Simulation to Predict Cyclic Variations written by Volker Sohm and published by Cuvillier Verlag. This book was released on 2007-07-06 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the first passenger car with internal combustion (IC) engine was developed over 120 years ago, the device has been significantly improved regarding efficiency, emissions, smoothness and ease of use. Today IC-engines are used in roughly 850 million passenger cars worldwide. Even though many other concepts as e.g. fuel cells are investigated, it seems that no system can replace IC-engines in the near and intermediate future. Two different combustion concepts are considered to have the potential to full fill future requirements with respect to fuel consumption and emission standards: turbo-charged diesel and stratified spark ignition (SI) engines with high pressure direct injection (DI) systems. Both systems can operate with overall lean air/fuel mixtures. The first DISI-engine in a passenger car used a homogeneous air/fuel mixture. It was implemented in 1951 in the models Gutbrod Superior and Goliath GP 700 leading to a significant reduction in fuel consumption. The first application in mass production of direct injection systems in SI-engines was in 1997 in the Mitsubishi Carisma GDI (gasoline direct injection). The greatest issues of stratified DISI-engines today, which give a much higher potential in fuel consumption economy compared to the homogeneous combustion concept, are combustion stability and emissions. Cycle-to-cycle variations of the gas motion have been identified to play a key role in the further optimization of the device since they have a great impact on the combustion process. Engine parameters are set according to the behavior of the mean cycle. However, the extreme engine cycles, cycles of greatest and slowest burning rates, determine the operating range of the engine. Consequently, the optimal spark timing, equivalence ratio and compression ratio are a compromise. A critical issue in stratified DISI-engines is that cyclic variations are substantial to the combustibility of the air/fuel mixture at the time of the discharge of the spark plug leading to partial burning or even misfire, which is undesirable in terms of engine roughness, efficiency and unburned hydrocarbon emissions. Computational fluid dynamics (CFD) with common Reynolds averaged Naviers-Stokes (RANS) turbulence modeling has been established to be a very efficient and reliable tool within the design process of IC-engines. I. e. optimization of engine geometries can be accomplished with a short turnaround time. Additionally, insights into various physical processes can be gained that are difficult to study experimentally. However, this approach is limited by definition if unsteady features such as cycle-to-cycle variations are investigated and cannot capture this kind of phenomenon. On the other hand, large eddy simulation (LES) provides the ability to predict cyclic variations because smaller spatial scales and temporal fluctuations are resolved. Since in LES a significantly smaller range of turbulent length scales needs to be modeled compared to the RANS approach, the accuracy of LES is superior to RANS. However, resolving smaller temporal and spatial scales requires higher order numerical schemes, smaller time steps and higher resolutions of the computational grids. This can lead to a significant increase of CPU time compared to RANS. For wall-bounded turbulent flows at high Reynolds number and in complex geometries hybrid RANS/LES approaches have become more and more popular in the recent years. They combine attractive features of both methods. These methods provide the opportunity to use LES in regions, where its performance is known to be essentially superior to RANS. In other regions, where the accuracy and the averaged information on turbulent properties is sufficient, RANS can be used in order to save CPU-time. In contrast to pure RANS temporal fluctuations can be resolved in the LES regions in hybrid methods giving these approaches the potential to predict cycle-to-cycle variations or other turbulent flows of highly unsteady nature. The present work focuses on unsteady turbulent flow phenomena in IC-engines such as cyclic variations of the gas motion and investigates the ability of subgrid turbulence modeling to predict those. In Chapter 2 the basic physical principles of fluid dynamics and turbulent flows are described both phenomenologically and based on the underlying governing equations. Furthermore, a review of filtering operations applied to the Navier Stokes equations and state of the art turbulence modeling is given. The different methods as well as the corresponding specific treatment of the boundary conditions of conventional RANS simulation and LES are presented and the hybrid RANS/LES method is introduced. The numerical requirements for the hybrid approach in terms of spatial and temporal schemes as well as the meshing method that is needed for the computation of flows in complex geometries with moving boundaries as in IC-engines are described in Chapter 3. Different numerical schemes of the CFD code CFX, which is used in this work, are evaluated and tested against the numerics of other commercial and academic codes. In Chapter 4 the hybrid method is tested against measurements and data of direct numerical simulation (DNS) for simple flow cases. For a fundamental evaluation of the approach classic turbulence test cases such as the decay of homogeneous isotropic turbulence and the flow past a backward-facing step are used. The most relevant flow configurations in engine development are the steady flow through an intake port/valve assembly and the transient flow in a reciprocating engine. However, before the hybrid method is applied to these complex turbulent flows in IC engines at high Reynolds number, simplified configurations of theses cases are investigated. The hybrid RANS/LES method is compared to RANS and LES computations in terms of accuracy and level of information on turbulence properties. Chapter 5 is dedicated to flows in IC-engines. The specific flow characteristics are described and quantified and key issues in engine design are discussed. The hybrid RANS/LES method is used for the computation of the steady flow through an intake port and the multi-cycle simulation of the flow in a series production BMW engine. Optical measurements are used to evaluate the quality of the averaged flow field of the simulation as well as the ability to predict cyclic variations of the gas motion in IC-engines.