Wavelet multi-resolution analysis on vortical structures of a dune wake based on large eddy simulation

The three-dimensional orthogonal wavelet multi-resolution technique was applied to analyze flow structures of various scales around an externally mounted vehicle mirror. Firstly, the three-dimensional flow of mirror wake was numerically analyzed at a Reynolds number of 105 by using the large-eddy simulation (LES). Then the instantaneous velocity and vorticity were decomposed into the large-, intermediate- and relatively small-scale components by the wavelet multi-resolution technique. It was found that a three-dimensional large-scale vertical vortex dominates the mirror wake flow and makes a main contribution to vorticity concentration. Some intermediate- and relatively small-scale vortices were extracted from the LES and were clearly identifiable.

Download Full-text

Large Eddy Simulation of the Wake Behind a Turning Ship

Volume 1: Fora, Parts A and B ◽

10.1115/fedsm2002-31272 ◽

2002 ◽

Cited By ~ 1

Author(s):

Ibrahim Yavuz ◽

Zeynep N. Cehreli ◽

Ismail B. Celik ◽

Shaoping Shi

Keyword(s):

Large Eddy Simulation ◽

Sensitivity Study ◽

West Virginia University ◽

Vortical Structures ◽

Turbulence Structures ◽

Eddy Simulation ◽

Flow Generation ◽

Large Eddy ◽

Unsteady Inflow ◽

Random Flow

This study examines the dynamics of turbulent flow in the wake of a turning ship using the large eddy simulation (LES) technique. LES is applied in conjunction with a random flow generation (RFG) technique originally developed at West Virginia University to provide unsteady inflow boundary conditions. As the ship is turning, the effects of the Coriolis and centrifugal forces on vortical structures are included. The effects of the Coriolis force on the flow-field are assessed and a grid sensitivity study is performed. The predicted turbulence structures are analyzed and compared with the wake of a non-turning ship.

Download Full-text

Large Eddy Simulation of Round Impinging Jets With Large Stand-Off Distance

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-37194 ◽

2014 ◽

Author(s):

Mehrdad Shademan ◽

Vesselina Roussinova ◽

Ron Barron ◽

Ram Balachandar

Keyword(s):

Large Eddy Simulation ◽

Flow Characteristics ◽

Impinging Jet ◽

Impinging Jets ◽

Vortical Structures ◽

Nozzle Height ◽

Eddy Simulation ◽

Large Eddy ◽

The Mean ◽

Good Agreement

Large Eddy Simulation (LES) has been carried out to study the flow of a turbulent impinging jet with large nozzle height-to-diameter ratio. The dynamic Smagorinsky model was used to simulate the subgrid-scale stresses. The jet exit Reynolds number is 28,000. The study presents a detailed evaluation of the flow characteristics of an impinging jet with nozzle height of 20 diameters above the plate. Results of the mean normalized centerline velocity and wall shear stress show good agreement with previous experiments. Analysis of the flow field shows that vortical structures generated due to the Kelvin-Helmholtz instabilities in the shear flow close to the nozzle undergo break down or merging when moving towards the plate. Unlike impinging jets with small stand-off distance where the ring-like vortices keep their interconnected shape upon reaching the plate, no sign of interconnection was observed on the plate for this large stand-off distance. A large deflection of the jet axis was observed for this type of impinging jet when compared to the cases with small nozzle height-to-diameter ratios.

Download Full-text

Large-Eddy Simulation of Three-Dimensional Vortical Structures for an Impinging Transverse Jet in the Near Region

Journal of Hydrodynamics ◽

10.1016/s1001-6058(07)60064-x ◽

2007 ◽

Vol 19 (3) ◽

pp. 314-321 ◽

Cited By ~ 10

Author(s):

Jing-yu Fan ◽

Yan Zhang ◽

Dao-zeng Wang

Keyword(s):

Large Eddy Simulation ◽

Three Dimensional ◽

Vortical Structures ◽

Transverse Jet ◽

Eddy Simulation ◽

Large Eddy

Download Full-text

Large Eddy Simulation of a Vortex Ring Impacting a Bump

Advances in Applied Mathematics and Mechanics ◽

10.4208/aamm.2013.m285 ◽

2014 ◽

Vol 6 (3) ◽

pp. 261-280

Author(s):

Heng Ren ◽

Ning Zhao ◽

Xi-Yun Lu

Keyword(s):

Large Eddy Simulation ◽

Vortex Ring ◽

Three Dimensional ◽

Vortical Flow ◽

Flow State ◽

Vortical Structures ◽

Eddy Simulation ◽

Large Eddy ◽

Flow Phenomena ◽

Flow Evolution

AbstractA vortex ring impacting a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial diameter and translational speed of the vortex ring. The effects of bump height and vortex core thickness for thin and thick vortex rings on the vortical flow phenomena and the underlying physical mechanisms are investigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The boundary vorticity flux is analyzed to reveal the mechanism of the vorticity generation on the bump surface. The circulation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Further, the analysis of turbulent kinetic energy reveals the transition from laminar to turbulent state. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the flow evolution and the flow transition to turbulent state.

Download Full-text