Large Eddy Simulation: Flow over a cylinder¶
Overview¶
The purpose of this numerical simulation is to validate the following parameters of incompressible Large Eddy Simulation (LES) of flow over a cylinder:
 Pressure distribution on the surface
 Streamwise Velocity distribution in the wake
The numerical simulation results of SimScale were compared with the experimental results. The flow regime selected for the study is classified as subcritical with a flow reynold number of \(Re=3900\).
Geometry¶
The geometry of the study is a straight cylindrical body (see Fig.1.). A brief description of the dimensions is provided by the table below.
Length  Diameter  

Value [m]  \(\pi D\)  0.1 
Domain and Analysis type¶
An Otype domain was selected as the flow domain around the cylinder. The domain was \(15D\) in the radial direction and \(\pi D\) in the spanwise direction (see Fig.2.). For this study a structured hexahedral mesh was created with the open source ‘BlockMeshtool’. The grid nodes are distributed by a geometric grading in the radial direction. Further, the nodes are clustered near the stagnation point and in the wake region along the streamwise direction. The mesh is based on a yplus (\(y^+\)) criterion of \(y^+ < 1\) in the radial direction. The complete details of the mesh are listed in the following table:
Mesh and Element types :
Mesh type  Cells in radial  Cells in circumferential  Cells in spanwise  Number of nodes  Type 

blockMesh  165  204  34  1144440  3D hexahedral 
The numerical analysis performed is detailed as follows:
Tool Type : OPENFOAM®
Analysis Type : Incompressible Large Eddy Simulation
SubGridScale Model : Smagorinsky with CubeRootVolume delta
Simulation Setup¶
Fluid:
 Air: Dynamic viscosity (\(\nu\)) \(= 1.511^{5} m^2s\)
Boundary Conditions:
The inlet boundary was set as a nonturbulent fixed velocity condition, while a pressure boundary condition was applied at the outlet. For the spanwise boundaries a symmetry condition was applied. The following table provides the further details.
Boundary type  Velocity  Pressure 

Inlet  Fixed Value: \(0.59\ ms^{1}\)  Zero Gradient 
Outlet  inletOutlet  Fixed Value: \(0\ Pa\) 
Wall noslip  Fixed Value: \(0.0\ ms^{1}\)  Zero Gradient 
Symmetry 
Results¶
The numerical simulation results of mean pressure distribution and mean streamwise velocity are compared with experimental data provided by C.Norberg [1] , L.Ong and J.Wallace [2] and L.M.Lourenco and C.Shih [3] . To ensure meaningful results, averaging was carried out over periods of atleast \(100D/U_\infty\) time units or about 21 vortex shedding cycles.
A comparison of the mean pressure distribution obtained with SimScale and experimental results is given in Fig.3A. The mean streamwise velocity profile is compared with experimental data as shows by the Fig.3B.
Fig.3. Pressure distribution comparison (left), streamwise velocity profile comparison (right)
The instantaneous vorticity component \(w_z\), and averaged streamlines in the crosssection (xy plane) are shown by the Fig.4A and Fig.4B respectively.
A visualization of the instantaneous flow field is shown along the crosssectional and spanwise planes provided by Fig.5A and Fig.5B.
Fig.5. Instantaneous flow field along streamwise (left), and along span directions (right)
References¶
[1] 

[2] 

[3]  L.M. Lourenco and C. Shih, ‘Characteristics of the plane turbulent near wake of a circular cylinder, a particle image velocimetry study’, Private Communication, 1993. 
Disclaimer¶
This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software and owner of the OPENFOAM® and OpenCFD® trade marks. OPENFOAM® is a registered trade mark of OpenCFD Limited, producer and distributor of the OpenFOAM software.