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This book presents recent progress in the application of RANS turbulence models based on the Reynolds stress transport equations. A variety of models has been implemented by different groups into different flow solvers and applied to external as well as to turbo machinery flows. Comparisons between the models allow an assessment of their performance in different flow conditions. The results demonstrate the general applicability of differential Reynolds stress models to separating flows in industrial aerodynamics.
Proceedings of the world renowned ERCOFTAC (International Symposium on Engineering Turbulence Modelling and Measurements). The proceedings include papers dealing with the following areas of turbulence: · Eddy-viscosity and second-order RANS models · Direct and large-eddy simulations and deductions for conventional modelling · Measurement and visualization techniques, experimental studies · Turbulence control · Transition and effects of curvature, rotation and buoyancy on turbulence · Aero-acoustics · Heat and mass transfer and chemically reacting flows · Compressible flows, shock phenomena · Two-phase flows · Applications in aerospace engineering, turbomachinery and reciprocating engines, industrial aerodynamics and wind engineering, and selected chemical engineering problems Turbulence remains one of the key issues in tackling engineering flow problems. These problems are solved more and more by CFD analysis, the reliability of which depends strongly on the performance of the turbulence models employed. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation. As in other fields of Science, in the rapidly developing discipline of turbulence, swift progress can be achieved only by keeping up to date with recent advances all over the world and by exchanging ideas with colleagues active in related fields.
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.
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.
This work seeks to improve the prediction of turbulent boundary layer flows under adverse pressure gradients (APG) encountered in the aeronautical industry, especially towards the trailing edge of wings. Indeed, the inaccurate prediction of such flows results in inaccurate predictions of aircraft performance and of the limits of the flight domain. To reduce the design margins and enable optimal aircraft geometries, the reliability of turbulence models in APG boundary layers has to be improved.The relevance of second-moment closures of the RANS equations, also called Reynolds-stress models (RSM), aiming at reproducing more accurately the physics of the flow, is therefore assessed for industrial use. Three Reynolds-stress models that differ in their near-wall modelling and in their length-scale providing equation, namely the EB-RSM, the SSG/LRR-omega RSM and the SSG-omega ATAAC RSM, are first benchmarked on two academic test cases, a flat plate and the APG boundary layer at equilibrium of the Skåre & Krogstad experiment, against the Spalart-Allmaras model and the reference data. These academic cases highlight the fundamental differences between the models and their impact on the profiles and integral quantities of the boundary layer. In particular, the Reynolds-stress profiles and the turbulence budgets in the flat plate test case demonstrate the effectiveness of near-wall modelling. However, the Skåre & Krogstad test case shows the necessity to improve the prediction of velocity profiles in the log region and of skin friction in strong APG flows, despite an excellent prediction of the boundary layer growth.A correction for the log-law region, corresponding to a local recalibration of the model constants in APG regions, is first explored to ensure the correct velocity gradient in APG log layers. The correction is investigated with the Spalart-Allmaras model using a NACA 4412 test case. Despite satisfactory results, the correction is shown to be difficult to generalise to other models and that its impact on the flow prediction is limited to low-Reynolds-number cases, thus restricting its relevance for the aeronautical industry.The two-equation eddy-viscosity models and RSMs are shown to be incompatible with the square-root layer, which progressively grows at the outer end of the log layer in APG boundary layers. A correction locally introducing a pressure-diffusion term is therefore investigated analytically and assessed on the RSMs considered using the Skåre & Krogstad test case. A new model, the EB-RSM-dP, is here defined as a corrected version of the EB-RSM and exhibits improved predictions regarding the velocity and Reynolds-stress profiles and the boundary layer quantities.The standard and corrected RSMs are compared to the Spalart-Allmaras model on an application case, the Common Research Model, representative of a commercial aircraft, and demonstrate the relevance of such models for the aeronautical industry with improved pressure distribution on the wing and reduced errors in the drag-due-to-lift predictions. The square-root-law correction is here validated with the SSG/LRR-omega-dP of Knopp et al. (2018) and the newly developed EB-RSM-dP, and shows significant improvement of the aerodynamic load on the wing, and of both the lift and drag predictions for the highest Reynolds number configuration, compared to the uncorrected models. This study also highlights the strong impact of the activation region of the correction on the results.
This volume offers of the EU-funded 5th Framework project, FLOMANIA (Flow Physics Modelling – An Integrated Approach). The book presents an introduction to the project, exhibits partners’ methods and approaches, and provides comprehensive reports of all applications treated in the project. A complete chapter is devoted to a description of turbulence models used by the partners together with a section on lessons learned, accompanied by a comprehensive list of references.
This self-contained, interdisciplinary book encompasses mathematics, physics, computer programming, analytical solutions and numerical modelling, industrial computational fluid dynamics (CFD), academic benchmark problems and engineering applications in conjunction with the research field of anisotropic turbulence. It focuses on theoretical approaches, computational examples and numerical simulations to demonstrate the strength of a new hypothesis and anisotropic turbulence modelling approach for academic benchmark problems and industrially relevant engineering applications. This book contains MATLAB codes, and C programming language based User-Defined Function (UDF) codes which can be compiled in the ANSYS-FLUENT environment. The computer codes help to understand and use efficiently a new concept which can also be implemented in any other software packages. The simulation results are compared to classical analytical solutions and experimental data taken from the literature. A particular attention is paid to how to obtain accurate results within a reasonable computational time for wide range of benchmark problems. The provided examples and programming techniques help graduate and postgraduate students, engineers and researchers to further develop their technical skills and knowledge.
Turbulence is one of the key issues in tackling engineering flow problems. As powerful computers and accurate numerical methods are now available for solving the flow equations, and since engineering applications nearly always involve turbulence effects, the reliability of CFD analysis depends increasingly on the performance of the turbulence models. This series of symposia provides a forum for presenting and discussing new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. The papers in this set of proceedings were presented at the 5th International Symposium on Engineering Turbulence Modelling and Measurements in September 2002. They look at a variety of areas, including: Turbulence modelling; Direct and large-eddy simulations; Applications of turbulence models; Experimental studies; Transition; Turbulence control; Aerodynamic flow; Aero-acoustics; Turbomachinery flows; Heat transfer; Combustion systems; Two-phase flows. These papers are preceded by a section containing 6 invited papers covering various aspects of turbulence modelling and simulation as well as their practical application, combustion modelling and particle-image velocimetry.
Large Eddy Simulation (LES) is a high-fidelity approach to the numerical simulation of turbulent flows. Recent developments have shown LES to be able to predict aerodynamic noise generation and propagation as well as the turbulent flow, by means of either a hybrid or a direct approach. This book is based on the results of two French/German research groups working on LES simulations in complex geometries and noise generation in turbulent flows. The results provide insights into modern prediction approaches for turbulent flows and noise generation mechanisms as well as their use for novel noise reduction concepts.