Large eddy simulation of the near wake of a rectangular wing

1998 ◽  
Author(s):  
K. Youssef ◽  
S. Ragab ◽  
W. Devenport ◽  
A. Abde
Keyword(s):  
Large Eddy Simulation ◽  
Near Wake ◽  
Eddy Simulation ◽  
Large Eddy

A Large-Eddy Simulation of the Near Wake of a Circular Cylinder

1998 ◽  
Vol 120 (2) ◽  
pp. 243-252 ◽  
Author(s):  
S. A. Jordan ◽  
S. A. Ragab
Keyword(s):  
Circular Cylinder ◽  
Large Eddy Simulation ◽  
Dynamic Model ◽  
Curvilinear Coordinates ◽  
Reynolds Stresses ◽  
Near Wake ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Global And Local

The formation and the downstream transport of the Strouhal vortices in the near wake of a circular cylinder are investigated using the large-eddy simulation (LES) method. The governing equations are formulated in curvilinear coordinates to accommodate a nonorthogonal grid with formal development of a dynamic model to account for the subgrid turbulent scales. Results were produced with and without use of the model. The focus of the investigation is at a subcritical Reynolds number of 5600. Using the dynamic model, the LES results compared best to the published experimental data in terms of both the global and local wake characteristics such as the drag and base pressure coefficients, shedding and detection frequencies, peak vorticity, and the downstream mean velocity-defect and Reynolds stresses. The results further showed streamwise filaments that connect subsequent Strouhal vortices. Qualitatively, the time-averaged Reynolds stresses of the formation region revealed similar symmetric characteristics over the range 525 ≤ Re ≤ 140,000.

The Role of Inflow Turbulence for Large Eddy Simulation on Modelling of Bluff Body Flows

2004 ◽  
Author(s):  
Mustafa Tutar ◽  
Ismail Celik ◽  
Ibrahim Yavuz
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Boundary Conditions ◽  
Turbulent Flow ◽  
Bluff Body ◽  
Near Wake ◽  
Local Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inflow Turbulence

A random flow generation (RFG) technique for large eddy simulation (LES) is successfully adopted into a finite element based conventional fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the LES computations of viscous incompressible turbulent flow over a two-dimensional circular cylinder at Reynolds number of 140,000. The effect of generated turbulent inflow boundary conditions on the transitional nature of the flow regime is studied during the early development of the very near wake of the cylinder. The numerical results obtained from the Smagorinsky sub-grid scale (SGS) model based simulations are compared with each other and with the experimental data for varying degree of inflow turbulence to discuss the issues such as the inflow turbulence effects on the time evolution of the local flow structures in the very near wake and on the integral flow parameter predictions such as separation points, transient fluid forces that the cylinder experience, and the local flow resolutions in the vicinity of the cylinder wall and the free shear layer. The influence of mesh resolution on the quality of the predicted results is also investigated. The comparison of present LES results with those of case without inflow turbulence and the experimental data indicates that the present LES approach coupled with the suggested RFG technique enhance the resolution of the turbulent flow and can be used with a confidence for a bluff body problem where the inflow turbulence is significant.

Large Eddy Simulation of Flow Past Free Surface Piercing Circular Cylinders

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
G. Yu ◽  
E. J. Avital ◽  
J. J. R. Williams
Keyword(s):  
Reynolds Number ◽  
Free Surface ◽  
Large Eddy Simulation ◽  
Froude Number ◽  
Drag Force ◽  
Surface Effect ◽  
Circular Cylinders ◽  
Near Wake ◽  
Eddy Simulation ◽  
Large Eddy

Flows past a free surface piercing cylinder are studied numerically by large eddy simulation at Froude numbers up to FrD=3.0 and Reynolds numbers up to ReD=1×105. A two-phase volume of fluid technique is employed to simulate the air-water flow and a flux corrected transport algorithm for transport of the interface. The effect of the free surface on the vortex structure in the near wake is investigated in detail together with the loadings on the cylinder at various Reynolds and Froude numbers. The computational results show that the free surface inhibits the vortex generation in the near wake, and as a result, reduces the vorticity and vortex shedding. At higher Froude numbers, this effect is stronger and vortex structures exhibit a 3D feature. However, the free surface effect is attenuated as Reynolds number increases. The time-averaged drag force on the unit height of a cylinder is shown to vary along the cylinder and the variation depends largely on Froude number. For flows at ReD=2.7×104, a negative pressure zone is developed in both the air and water regions near the free surface leading to a significant increase of drag force on the cylinder in the vicinity of the free surface at about FrD=2.0. The mean value of the overall drag force on the cylinder increases with Reynolds number and decreases with Froude number but the reduction is very small for FrD=1.6–2.0. The dominant Strouhal number of the lift oscillation decreases with Reynolds number but increases with Froude number.

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