ANSYS Turbulence

Turbulence ModelingIndustry Solutions ANSYS fluid dynamics technology is a leader in turbulent flow modeling, with an industry-tested suite of turbulence models covering even the most complex flows. Steady-State Turbulence Models Turbulence has a strong effect on flow characteristics of interest to engineers, such as drag or lift of aerodynamic bodies, mixing of chemical components, heat transfer and combusting processes. Most engineering flows are turbulent, and these flows are inherently random, three-dimensional and unsteady. Such unsteady motion is composed of a wide range of spatial and temporal scales. It may take many decades — or more — for these physics to be computationally resolved for practical engineering applications. Until then, however, it is essential to accurately account for turbulence effects in computational fluid dynamics (CFD) by using various types of approximations in the form of turbulence models. ANSYS offers a number of advanced turbulence models in the form of algebraic, one-equation, two-equation and Reynolds stress models. These models are integrated into state-of-the-art CFD solvers. The most widely used turbulence models are Reynolds-averaged Navier–Stokes (RANS) models that are based on time-averaging of the equations. Time-averaging filters out all turbulent scales from the simulation, and the effect of turbulence on the mean flow is then re-introduced through appropriate modeling assumptions. The prediction of flow separation for equipment and parts such as wings, vehicles and manifolds is very important because the operating performance of the entire machine is affected by this behavior. For flow separation, the shear–stress transport (SST) model has become accepted as the two-equation model industry standard. The SST model unifies the advantages of the most widely employed two-equation (k-ω and k-ε) models and is the most reliable model for fluids with flow separation. Consistent definition of near-wall processes allows accurate prediction of heat transfer between the walls of solid parts and internal or external flow. The use of ANSYS turbulence models in combination with the ANSYS CFD advanced numerical solvers provides a reliable and accurate basis for flow analysis. Pressure contours and pathlines Turbulent mixing Courtesy Forschungszentrum Rossendorf e.V. Vortex structures in a four-stroke engine just after injection of fuel and intake valve opening Courtesy BMW Group The model was originally developed in CFD software from ANSYS. In these cases. ANSYS has pioneered the development of a new class of models that allow the reliable prediction of the onset and extent of laminar–turbulent transition even in complex applications. With one simulation using this SST-based turbulence transition model. Institute of Combustion Technology. so the company’s products offer a unique advantage in model accuracy. and free-shear and mixed layer flows. engineers can calculate laminar and turbulent flows including transition. it is advantageous to resolve the vortex structures of turbulence to a certain extent. therefore. Software from ANSYS offers a wide range of SRS models: • Scale-adaptive simulation (SAS) • Detached eddy simulation (DES) • Large eddy simulation (LES) and wall-modeled LES (WMLES) • Zonal and embedded LES models Turbulence structures in a singleswirl burner . wings and many other applications often features upstream laminar boundary layers that transition into a turbulent flow further downstream. State-of-the-art best practice in SRS modeling includes the application of hybrid models such as SAS and DES. This model considers three important factors that cause transition: • Natural transition: classical transition in the boundary layer • Bypass transition: transition due to a turbulence transport into the (laminar) boundary layer Vortex structures generated by aircraft landing gear • Separation-induced transition: transition induced by flow separation The turbulence transition model closes the gap between laminar and turbulent flows and significantly expands the range of applications for fluid flow software from ANSYS. . Using these models. Mixing in swirl combustion chambers and the separated flow behind a car are examples in which SRS models provide a significant improvement in results when compared to steady-state RANS models. transient turbulence models — also called scale-resolving simulation (SRS) models — are recommended. To aid in analyzing this widely observed physical behavior. A precessing vortex core colored by axial velocity in an SAS simulation of a combustion chamber Courtesy German Aerospace Center (DLR). The company continually improves and enhances this model to maintain its lead in this critical area. partial resolution of turbulence is possible and is limited only by mesh size and time increment. quality and consistency of performance that only the creator who fully understands the model can provide. are easier to describe by a model.Industry Solutions Laminar–Turbulent Transition Models The flow around turbine blades. Turbulence can be modeled if grid and time parameters are below the threshold limits. These methods are advantageous because smaller scales do not contribute significantly to the overall flow development and. flows with large separation zones. Transient Turbulence Models For swirl flows. The cooperative agreement enables ANSYS to quickly transfer new technologies into its most recently released software products. and industrially applicable scale-resolving simulation methods.002 In addition to existing SAS. Menter. . He and his team have contributed substantially to the formulation of robust and accurate turbulence models for a wide range of industrial applications. In addition. DES and LES models. consistency of implementation and careful validation across the spectrum of industrial applications. ANSYS has recently introduced an industry first — wall-modeled LES (WMLES) and embedded LES (ELES). ANSYS maintains close links to the originators of the DES approach. Image is colored by wall shear stress with laminar separation bubbles indicated. ANSYS actively participates in a long-term cooperation with the NTS group — a leader in unsteady flow modeling and one of the originators of DES methodology — of Prof. 0 0 2e+05 4e+05 Rex 6e+05 8e+05 1e+06 Influence of the transition model in predicting the friction coefficient Embedded LES (ELES) for the NASA hump flow experiment with synthetic turbulence generated at the RANS–LES interface Simulation performed for the EU project ATAAC. a widely recognized leader in the advancement of engineering turbulence models. Florian R. The ANSYS team for turbulence model development is led by Dr. Contributions include y+-insensitive wall formulations.004 0. The joint development covers improved RANS models as well as latest-generation scale-resolving methods.008 0. The ANSYS Turbulence Team ANSYS delivers an unparalleled breadth of leading models to capture the effects of turbulence accurately and efficiently. The SAS model is capable of resolving largescale turbulent structures without the time and grid-scale resolution restrictions of LES. 0. while covering less critical areas with RANS. which minimize the sensitivity of results to the near-wall grid resolution.Industry Solutions 0. novel models for laminar–turbulent transition prediction. Petersburg. which maintains optimal implementation quality. now an industrial standard in the aeronautics and astronautics community. advanced one. He is the originator of the SST turbulence model. NTS and ANSYS test the model in independent codes. often allowing the use of existing grids created for RANS simulations. This restricts the computationally expensive LES part to regions where it is truly required. Michael Strelets at the University of St.and two-equation models for aerodynamic simulations. The ANSYS turbulence team is continually engaged in high-level research and development projects and interacts directly with leaders in the turbulence research community. ELES and zonal LES offer even more flexibility by allowing an embedded LES zone within a larger RANS domain. WMLES allows the simulation of wall-bounded flows at much higher Reynolds numbers than classical LES and thereby removes one of the most severe restrictions of LES with respect to industrial simulations. Dr. Menter and his team help ensure that ANSYS turbulence models remain at the leading edge of the technology and offer the highest quality in terms of model formulation. using the SST-based laminar–turbulent transition model. and the company works continually to increase accuracy of these models for complex engineering flow simulations.01 Boundary Layer Code Experiment Laminar Turbulent 0.006 Cf ANSYS is leading the engineering simulation sector in the development of SAS modeling — the most attractive and easy-to-use approach to unsteady flow simulations. Simulation of a wing–body with high-lift devices for the AIAA High Lift Prediction Workshop (HiLiPW-1). Inc. Printed in U. 724.9724 Toll Free Mexico: 001.A.Geometry courtesy CADFEM.S. This technology is available in the ANSYS Workbench platform. Inc.S.267. deploying the world’s most comprehensive multiphysics solutions to solve their complex engineering challenges. 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