scholarly journals An Effective Three-Dimensional Layout of Actuation Body Force for Separation Control

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Ittetsu Kaneda ◽  
Satoshi Sekimoto ◽  
Taku Nonomura ◽  
Kengo Asada ◽  
Akira Oyama ◽  
...  
Keyword(s):  
Body Force ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Separated Flow ◽  
Flow Fields ◽  
The Body ◽  
Large Eddy Simulations ◽  
Separation Control ◽  
Large Eddy

We conducted large eddy simulations of the control of separated flow over an airfoil using body forces and discuss the role of a three-dimensional vortex structure in separation control. Two types of cases are examined: (1) the body force is distributed in a spanwise uniform layout and (2) the body force is distributed in a spanwise intermittent layout, with three-dimensional vortices being expected to be generated in the latter cases. The flow fields in the latter cases have a shorter separation bubble than those in the former cases although the total momentum of the body force in the latter cases is the same as or half of the former cases. In the flow fields of the latter type, the three-dimensional vortices, which are not observed in the former cases, are generated by the body force downstream of the body force distributed. Thus, three-dimensional vortices are considered to be effective in controlling the separated flow.

Reliable and Accurate Prediction of Three-Dimensional Separation in Asymmetric Diffusers Using Large-Eddy Simulation

2009 ◽  
Author(s):  
Hayder Schneider ◽  
Dominic von Terzi ◽  
Hans-Jo¨rg Bauer ◽  
Wolfgang Rodi
Keyword(s):  
Experimental Data ◽  
Reverse Flow ◽  
Separation Bubble ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

Reynolds-Averaged Navier-Stokes (RANS) calculations and Large-Eddy Simulations (LES) of the flow in two asymmetric three-dimensional diffusers were performed. The numerical setup was chosen to be in compliance with previous experiments. The aim of the present study is to find the least expensive method to compute reliably and accurately the impact of geometric sensitivity on the flow. RANS calculations fail to predict both the extent and location of the three-dimensional separation bubble. In contrast, LES is able to determine the amount of reverse flow and the pressure coefficient within the accuracy of experimental data.

scholarly journals Turbulent Flow Fields Over a 3D Hill Covered by Vegetation Canopy Through Large Eddy Simulations

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3624 ◽  
Author(s):  
Zhenqing Liu ◽  
Yiran Hu ◽  
Yichen Fan ◽  
Wei Wang ◽  
Qingsong Zhou
Keyword(s):  
Three Dimensional ◽  
Flow Fields ◽  
Large Eddy Simulations ◽  
Wind Tunnel Experiments ◽  
Turbulence Structures ◽  
Large Eddy ◽  
Turbulence Kinetic Energy Budget ◽  
The Mean ◽  
Spanwise Rotation ◽  
The Hill

The flow fields over a simplified 3D hill covered by vegetation have been examined by many researchers. However, there is scarce research giving the three-dimensional characteristics of the flow fields over a rough 3D hill. In this study, large eddy simulations were performed to examine the coherent turbulence structures of the flow fields over a vegetation-covered 3D hill. The numerical simulations were validated by the comparison with the wind-tunnel experiments. Besides, the flow fields were systematically investigated, including the examinations of the mean velocities and root means square of the fluctuating velocities. The distributions of the parameters are shown in a three-dimensional way, i.e., plotting the parameters on a series of spanwise slices. Some noteworthy three-dimensional features were found, and the mechanisms were further revealed by assessing the turbulence kinetic energy budget and the spectrum energy. Subsequently, the instantaneous flow fields were illustrated, from which the coherent turbulence structures were clearly identified. Ejection-sweep motion was intensified just behind the hill crest, leading to a spanwise rotation. A group of vertical rotations were generated by the shedding of the vortex from the lateral sides of the hill.

scholarly journals Waving plants and turbulent eddies

2010 ◽  
Vol 652 ◽  
pp. 1-4 ◽  
Author(s):  
J. J. FINNIGAN
Keyword(s):  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Plant Canopy ◽  
Turbulent Eddies ◽  
Plant Canopies ◽  
Large Eddy ◽  
Flexible Plant ◽  
Paradoxical Results

New large-eddy simulations of flow over a flexible plant canopy by Dupont et al. (J. Fluid Mech., 2010, this issue, vol. 652, pp. 5–44) have produced apparently paradoxical results. Work over the last three decades had suggested that turbulent eddies could ‘lock onto’ to the waving frequency of uniform cereal canopies. Their new simulations contradict this view, although a resolution may lie in the essentially three-dimensional nature of the instability process that generates the dominant eddies above plant canopies.

Nonboundary Conforming Methods for Large-Eddy Simulations of Biological Flows

2005 ◽  
Vol 127 (5) ◽  
pp. 851-857 ◽  
Author(s):  
Elias Balaras ◽  
Jianming Yang
Keyword(s):  
Body Surface ◽  
Computational Algorithm ◽  
The Body ◽  
Large Eddy Simulations ◽  
Moving Boundaries ◽  
Lagrangian Formulation ◽  
Governing Equations ◽  
Solid Interface ◽  
Large Eddy ◽  
Biological Flows

In the present paper a computational algorithm suitable for large-eddy simulations of fluid/structure problems that are commonly encountered in biological flows is presented. It is based on a mixed Eurelian-Lagrangian formulation, where the governing equations are solved on a fixed grid, which is not aligned with the body surface, and the nonslip conditions are enforced via local reconstructions of the solution near the solid interface. With this strategy we can compute the flow around complex stationary/moving boundaries and at the same time maintain the efficiency and optimal conservation properties of the underlying Cartesian solver. A variety of examples, that establish the accuracy and range of applicability of the method are included.

THE PLUNGING OF HYPERPYCNAL PLUMES ON TILTED BED BY THREE-DIMENSIONAL LARGE-EDDY SIMULATIONS

2020 ◽  
Author(s):  
Felipe Nornberg Schuch ◽  
Jorge Silvestrini ◽  
Eckart Meiburg ◽  
Sylvain Laizet
Keyword(s):  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Large Eddy
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