Vortex shedding

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Introduction

Mesh and velocity

This example is a two-dimensional steady-state laminar flow simulation of vortex shedding around a two-dimensional cylinder with a Reynolds number of 100.

The simulation conditions are as follows

  • solver : buoyantPimpleNFoam
  • turbulence model : laminar
  • Reynolds No. : 100

Start BaramFlow and load mesh

Run the program and select [New Case] from the launcher. In the launcher, select [Pressure-based] for [Solver Type] and [None] for [Multiphase Model].

Use the given polyMesh folder. In the top tab, click [File]-[Load Mesh]-[OpenFOAM] in that order and select the polyMesh folder.

General

Change Time to Transient.

Models

For this example, we’ll use Laminar for turbulence.

Materials

For this example, we use the condition of Reynolds number is 100 and velocity is 1.

Set the density and viscosity as follows

  • density : 1 $kg/m^3$
  • viscosity : 0.01 $kg/ms$

Boundary Conditions

Each boundary condition is set as follows

  • cylinder : Wall
    • Velocity Condition : No Slip

  • sym : Symmetry
  • out : Pressure Outlet
    • Total Pressure : 0 (Pa)

  • in : Velocity Inlet
    • Velocity Specification Method : Magnitudde, Normal to Boundary
    • Profile Type : Constant
    • Velocity Magnitude : 1 (m/s)

  • frontAndBackPlanes : Empty

Reference Values

Set the Reference Value for the aerodynamic coefficient calculation as follows.

  • Area : 1
  • Density : 1
  • Length : 1
  • Pressure : 0
  • Velocity : 1

Numerical Conditions

In this example, we’ll change the settings as shown below.

  • Use Momentum Predictor : active
  • Discretization Schemes
    • Time : Second Order Implicit
    • Pressure : Momentum Weighted Reconstruct
    • Momentum : Second Order Upwind
  • Max iterations per Time Step : 10
  • Number of Correctors : 2

Use default conditions for the rest.

Monitor

Monitor the Drag/Lift Coefficient acting on the cylinder and the velocity/pressure at a point 1 meter from the center of the cylinder.

Drag/Lift Coefficient

  • Select [Add]-[Forces] button.
  • Set the values as follows
    • Write Interval : 1
    • Lift Direction : 0 1 0
    • Drag Direction : 1 0 0
    • Center of Rotation : 0 0 0
    • Boundaries : cylinder

Velocity and Pressure

  • Select [Add]-[Points] button.
  • Set the values as follows
    • Write Interval : 1
    • Field : Pressure
    • Coordinate : 1 0 0

In the same way, set up Velocity Magnitude monitoring for the same point.

Initialization

Set X-Velocity as 1 and use default values for the rest.

Enter the value and click the Initialize button at the bottom. Then click the [File]-[Save] menu to save the case file.

Run

Change the values as shown below, and click [Start Calculation] button.

  • Time Stepping Method : Adaptive
  • Max Courant Number : 1
  • End Time : 150
  • Save Interval : 0.5
  • Data Write Format : Binary
  • Number of Cores : 4


Residuals


Monitorings

Post-processing

Draw the velocity and pressure distribution around the cylinder.

Click the parview button in [External tools] to open the paraview.

Change the [Case Type] to [Decomposed Case].

Change [Solid Color] to U or p_rgh and click [play] icon.