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
- Stream-wise 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 sub-critical with a flow reynold number of Re=3900
.
Import validation project into workspace
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] | πD
|
0.1 |
Domain and Analysis type
An O-type domain was selected as the flow domain around the cylinder. The domain was 15D
in the radial direction and πD
in the span-wise direction (see Fig.2.). For this study a structured hexahedral mesh was created with the open source ‘BlockMesh-tool’. 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 stream-wise direction. The mesh is based on a y-plus (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
Sub-Grid-Scale Model : Smagorinsky with Cube-Root-Volume delta
Simulation Setup
Fluid:
- Air: Dynamic viscosity (ν
) =1.511−5m2s
Boundary Conditions:
The inlet boundary was set as a non-turbulent 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 no-slip | Fixed Value: 0.0 ms−1
|
Zero Gradient |
| Symmetry |
Results
The numerical simulation results of mean pressure distribution and mean stream-wise 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∞
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 stream-wise 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 wz
, and averaged streamlines in the cross-section (x-y plane) are shown by the Fig.4A and Fig.4B respectively.
A visualization of the instantaneous flow field is shown along the cross-sectional and spanwise planes provided by Fig.5A and Fig.5B.
Fig.5. Instantaneous flow field along stream-wise (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.