Sarp ER, Doğukan T. KARAHAN, Ayşe G. GÜNGÖR

Türbülanslı Akışlar İçin Sonlu Hacimler Yöntemi Tabanlı Bir LES Çözücüsü

Bu çalışmada, pratik uygulamalarda karşılaşılan türbülanslı akışları çalışmak amacıyla geliştirilen büyük girdap benzetimi (large-eddy simulation, LES) çözücüsü lestr3d sunulmaktadır. Çözücü, sıkıştırılabilir LES denklemlerini sonlu hacimler yöntemi ile yapısal olmayan çözüm ağları üzerinde ikinci mertebeden şemalar ile çözmektedir. Çözücüde LES modeli olarak sıkıştırılabilir Smagorinsky, duvar uyumlu lokal girdap (wall-adapting local-eddy, WALE) viskozitesi ve k- denklemi modelleri bulunmaktadır. Kodun verimli bir şekilde paralel çalışması, METIS yazılımı ve Message- Passing Interface (MPI) kütüphaneleri ile sağlanmıştır. Kodun bir yüksek başarımlı hesaplama merkezi platformunda 896 çekirdeğe kadar ölçeklenebilir olduğu gösterilmiştir. Çözücünün doğrulaması kavite akışının benzetimi ile gerçekleştirilmiştir. K-denklemi ve WALE modelleri ile elde edilen sonuçlar, düşük ve yüksek çözünürlükteki çözüm ağlarında, literatürde var olan doğrudan sayısal benzetim verileri ve deneysel veriler ile iyi uyum göstermektedirler. Bunun akabinde, lestr3d’nin kabiliyetlerini göstermek amacıyla T106 türbin pali etrafındaki akış çalışılmıştır. Çözücünün, karmaşık geometrilerde benzetim yapabildiği, akıştaki yapıları ve akış istatistiklerini güvenilir bir şekilde çözebildiği gösterilmiştir. Özetle, lestr3d’nin karmaşık türbülans problemlerini çalışmak için değerli ve uzun vadeli bir yatırım olduğu gösterilmiştir.

A Finite Volume Based LES Solver for Turbulent Flows

This work presents a new large-eddy simulation (LES) solver, lestr3d, developed to study practical turbulent flow problems. lestr3d solves the compressible LES equations on unstructured grids using the finite volume method and second-order discretization schemes. The compressible Smagorinsky, wall-adapting local-eddy (WALE) viscosity, and k-equation models are available as sub-grid scale models. Efficient parallelization is accomplished using the METIS software and Message-Passing Interface libraries. lestr3d is shown to be scalable on a high-performance computing platform up to 896 cores. The validation and verification analysis of lestr3d is performed on the lid-driven cavity flow problem. The results show excellent agreement with available direct numerical simulation and experimental data for the cases of k-equation and WALE with low- and high-resolution grids respectively. Then, the flow over the T106 turbine blade is studied to showcase the capabilities of lestr3d. It is demonstrated that lestr3d is capable of performing simulations on complex geometries and reliably capture spatio-temporal evolution as well as the statistics of the flow. Overall, lestr3d is demonstrated to be a valuable long-term investment for studying complex turbulent flow problems.

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