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Numerical simulation of local scour around three circular cylinders in staggered array
Published in Silke Wieprecht, Stefan Haun, Karolin Weber, Markus Noack, Kristina Terheiden, River Sedimentation, 2016
H.S. Kim, M. Park, I. Kimura, Y. Shimizu, M. Nabi
In order to overcome the inherent limitation of URANS model, large eddy simulation (LES) or detached eddy simulation (DES) has been used because they resolve accurately the unsteadiness flow and the dynamics of horseshoe vortices (Escauriaza & Sotiropoulos 2011, Paik et al. 2010). Escauriaza & Sotiropoulos (2011) developed DES coupled with a bedload transport model which can consider the effects of the instantaneous flow in sediment transport. They simulated scour and morphodynamics around a cylindrical pier and results showed that the ripple dynamics which evolve from the interactions between turbulent horseshoe vortex and sediment bed are accurately reproduced. Kim et al. (2014) investigated the flow and local scour around cylinders using LES combined with sediment motion and morphodynamic models where sediment particles are assumed to spherical particles and the sediment motion is solved in a Lagrangian frame work. They showed that numerical results of the local scour depth and shape around the cylinder are significantly improved.
Investigation of flow noise with different turbulence models
Published in Petar Georgiev, C. Guedes Soares, Sustainable Development and Innovations in Marine Technologies, 2019
The accurate prediction of the flow noise levels depends on the determination of flow characteristics in detail. Flow structures have been simulated by employing various turbulence models. RANS (Realizable k-Epsilon, SST Omega), DES (Detached Eddy Simulation), and LES (Large Eddy Simulation) models are used for investigation of these structures within the turbulent flow. Flow analyses have been performed by utilizing finite volume method in three-dimensional domain.
The effect of covering structure in pantograph sinking platform on the aerodynamics of high- speed train
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Hongkang Liu, Shishang Zhang, Xifeng Liang, Yong Zou
The commercial software STAR-CCM+ 14.02 isemployed to simulate the turbulent flow around high-speed train. Detached Eddy Simulation (DES) is a hybrid method combing Reynolds-Averaged Navier–Stokes(RANS) model and Large Eddy Simulation (LES), which can guarantee the calculation accuracy at a relatively low computational cost. DES was commonly used in the existing previous research to simulate the turbulent flow around the trains (Flynn et al., 2014; Guo et al., 2020; Niu et al., 2020). Usually, RANS is active in the near wall region and LES is active in the vortex core region. However, the small size of the wall-parallel spacing will lead to incorrect simulation in which the near-wall flow is solved by LES. Besides, the SGS model may fail to replace the unsolved turbulence structure leading to modeled-stress depletion. Hence, the Delayed Detached Eddy Simulation (DDES) model with a delay function is put forward to solve the above problems. Furthermore, based on DDES, Improve Delayed Detached Eddy Simulation (IDDES) is proposed by adding WMLES, which can effectively process the grids in the logarithmic region and reduce the reliance on the grid. In this study, IDDES based on SST k-omega is employed to solve the flow field around high-speed train.
Numerical study of flow structure and pedestrian-level wind comfort inside urban street canyons
Published in Journal of the Royal Society of New Zealand, 2021
Purvi P. Pancholy, Kevin Clemens, Patrick Geoghegan, Mark Jermy, Miguel Moyers-Gonzalez, Phillip L. Wilson
Future studies, and especially case studies specific to planned construction, should make use of non-steady state CFD approaches. Large Eddy Simulation (LES) is a transient approach that is particularly effective at modelling the large-scale vorticity in the flow separated region behind a bluff body. The disadvantage to LES is that it requires an extremely large number of mesh elements that scale as the 1.8th power of the Reynolds Number () (Malik and Bushnell 2012). As a result, even with a significantly large computing capacity, LES can take many hours, days or even weeks to simulate flows over complex geometries. This can render it impractical for some flow studies. Detached Eddy Simulation (DES) is a hybrid approach that applies RANS models in the near-wall region, and LES modelling in the core turbulence regions, making it less computationally intensive than pure LES modelling. DES might provide good unsteady flow characterisation for building studies, if the turbulent regions can be identified apriori.
An adoption of the Spalart–Allmaras turbulence model for two- and three-dimensional free surface environmental flows
Published in Journal of Hydraulic Research, 2021
Adrien Bourgoin, Kamal El Kadi Abderrezzak, Sofiane Benhamadouche, Riadh Ata
In the turbulence community, Spalart and Allmaras are considered as the fathers of DES (detached eddy simulation), which is a compromise between fully LES and RANS approaches (by applying RANS approaches to wall regions and LES to far-field areas). The model presented here belongs to the RANS family; extending this turbulence model to improve its behaviour close to confined regions and in the vicinity of walls will be the focus of forthcoming studies. The adoption of the length scale (implicitly included in the production terms) so as to behave as an LES model for far-fields should also be investigated.