KB 001886 Transient Turbulence Models on Empire State Building URANS or DDES

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Subject: • Transient Turbulence Models: URANS or DDES? • • Comment: • • Description: • Turbulence modeling plays a vital role in computational fluid dynamics (CFD) by aiming to predict the behavior of turbulent flows. These models are crucial for creating efficient and safe engineering applications, such as analyzing and designing wind-structure interactions. There are several approaches to turbulence modeling, with three widely used models being the Reynolds-Averaged Navier-Stokes (RANS), Unsteady Reynolds-Averaged Navier-Stokes (URANS), and Delayed Detached Eddy Simulation (DDES). Each of these models has distinct characteristics and specific applications. • • RWIND employs URANS and DDES turbulence models as two applicable turbulence modeling approaches in structural engineering. These models are chosen for their ability to balance computational efficiency and accuracy, making them practical for a wide range of engineering applications. URANS offers a moderate computational cost while capturing large-scale transient phenomena, whereas DDES combines the strengths of both RANS and Large Eddy Simulation (LES) to provide detailed resolution of complex turbulent structures. By integrating these models, RWIND enhances its capability to simulate the dynamic and intricate behavior of wind-structure interactions, ensuring both efficiency and precision in its analyses. • • ► Image | Image 2: DDES Turbulence Model in RWIND https://www.dlubal.com/en/img/051697 • • ==== URANS (Unsteady Reynolds-Averaged Navier-Stokes) ==== • URANS builds on the RANS method by accommodating time-dependent changes in the flow field, allowing it to capture unsteady phenomena. It still employs Reynolds averaging but does not time-average the flow as strictly as RANS. This allows URANS to model larger-scale transient flow features and oscillatory behaviors, such as vortex shedding from building corners. Although URANS offers improvements over RANS in capturing unsteadiness, it still uses eddy-viscosity models that may not adequately resolve finer turbulent structures. • • ==== DDES (Delayed Detached Eddy Simulation) ==== • DDES is a hybrid method that integrates RANS and Large Eddy Simulation (LES) techniques. In regions with an attached boundary layer, DDES functions like a RANS model, ensuring computational efficiency. In areas where the flow detaches and larger turbulent structures prevail, DDES switches to an LES mode for more accurate resolution. This approach is particularly effective for complex flows involving separation, reattachment, and wake regions, such as around building edges and corners. DDES strikes a good balance between computational cost and accuracy, making it suitable for simulating high Reynolds number flows with significant unsteady and separated regions. • • ==== Advantages and Disadvantages of URANS and DDES ==== • • '''URANS Advantages''' • • Time-Dependent Capabilities: URANS can capture unsteady phenomena and transient flow features, such as vortex shedding, which RANS cannot. • Moderate Computational Cost: While more computa... • • ► More Information: https://www.dlubal.com/en-US/support-... • ► All Knowledge Base Articles: https://www.dlubal.com/en-US/support-... • • Did you find this video helpful? • ► Then we would appreciate your comments and likes. • • E-Learning Videos: • ► RFEM 6 for Beginners: • E-Learning | RFEM 6 Tutorial for Begi... • ► Programming with RFEM 6 and Python: • E-Learning | Programming with RFEM 6 ... • ► RFEM 6 Tutorial with Rhino Grasshopper: • E-Learning | RFEM 6 Tutorial with Rhi... • • Take advantage of our free support. Do you have any questions? • ► Frequently Asked Questions (FAQ): https://www.dlubal.com/en/support-and... • ► Ask Individual Question: https://www.dlubal.com/en/support-and... • ► Knowledge Base: https://www.dlubal.com/en-US/support-... • • Follow us and stay up to date: • ► Subscribe to the Dlubal YouTube Channel: https://www.youtube.com/user/DlubalEN... • ► Instagram: / dlubal_software • ► Are you also on Facebook? Follow us here: / dlubal.software.english • • Keywords • #DlubalKnowledgeBase #Wind #RWIND #URANS #DDES #DlubalKB #KNOWLEDGEBASE #TechnicalArticle #Construction #CivilEngineering #StructuralEngineer #StructuralDesign #StructuralEngineer #StructuralAnalysis #RFEM6 #RSTAB9 #DlubalSoftware

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