Presentation on theme: "Advanced CFD Analysis of Aerodynamics Using CFX"— Presentation transcript:
1 Advanced CFD Analysis of Aerodynamics Using CFX Jorge Carregal FerreiraAchim Holzwarth, Florian Menter
2 Outline CFX: Advanced CFD software Turbulence Modells in CFX The companyThe productsTurbulence Modells in CFXNear wall treatment in CFXExamples:Duct with adverse pressure gradientAirfoilsHeat transfer
3 CFX: Member of AEA Technology Engineering SoftwareComputational Fluid DynamiXPlant Simulation Software
4 CFX: Global PositionCFD (Computational Fluid Dynamics) group of AEA TechnologyLargest European CFD company210 employees8 main officesStrong industrial presenceGrowth rate approx. 25% per yearMore than 1500 installed licenses
6 Leading Technology in CFX-5 Easy to usePre-Processor CFX-Build based on MSC.Patran:Unstructured hybrid gridsCoupled algebraic multigrid-solver (AMG): Accurate, robust and fastSolution time scales linear with grid sizeExcellent parallel performanceGrid adaptationUNIX, NT, LinuxHEXTETWEDGEPYRAMID
7 Leading Technology in CFX-5 Laminar and turbulent flows.Stationary and transient solutions.Large variaty of turbulence models.Transport equations for additional scalars.Multi-component and multi-phase fluids.Coupling with solid heat conduction.Solution depended mesh adaptation.Linear scaling of solver with grid size.Scalable parallel performance.
8 Preprocessing with CFX-Build Geometry modeller basedOn MSC.PatranNative CAD interfaces:Pro/Engineer, CATIA,Unigraphics, IDEAS, etc.
9 Turbulence Models in CFX-5 Release of the latest turbulence modelsk- Model Variantsk- Model and BSL Model (Wilcox, Menter)SST Model (Menter, Blending between k- and k-)Reynolds Stress ModelsExtended near-wall treatmentsScalable wall functions for k-Automatic near-wall treatment for k- and SSTLES model (Smagorinski)Documented validation cases on these models are availableFuture: Improved LES and transition modelling
10 Problems of Standard k- Model Two Problems:Missing transport effects.Too large length scales.Result:Reduced or omitted separation.Very often: Too optimistic machine performance.
15 Optimal Two Equation Model Combination of k-w and k-e model:k-w model near the surfacek-e model for free shear flows (e equation is transformed to w)Blending is performed automatically based on solution and distance from the surface.This model is called “Baseline Model – BSL”Combined with “Shear-Stress-Transport” limiter offers optimal boundary layer simulation capabilities.BSL+Limiter gives SST model.
16 Experiment Gersten et al. Diffuser Flow, 1k-e modelSST modelExperiment Gersten et al.
18 Wall Boundary Treatment Standard wall function boundary conditions are the single most limiting factor in industrial CFD computations regarding accuracy!“y+ has to be between 25 and 500” type statements are problematic!Boundary layer resolution requirements have to be satisfied.Log. Profile assumptions have to be satisfied.To satisfy both at the same time is the challenge.
19 Scaling of Variables near Wall Log. regionOuter regionSub-layer