한국어

Transient Flow

Vortex shedding

Introduction

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.

Time dependen Boundayr Condition

Download mesh

Download simulation

Introduction

This example sets up a boundary condition where the velocity and temperature at the inlet change over time.

It uses the pitzDaily mesh from the OpenFOAM tutorial.

The computational conditions are as follows

solver : buoyantPimpleNFoam
turbulence model : \(Standard\) \(k-\epsilon\)
density : Perfect Gas
viscosity : 1.79e-5 \(kg/ms\)

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 \(Standard\) \(k-\epsilon\) model for turbulence.

Change Eergy to Include.

Materials

For this example, we will use the properties of air.

Density : Perfect Gas (m/s)
Specific Heat (Cp) : 1004 \(J/kgK\) (m/s)
Viscosity : 1.79e-05 \(kg/ms\)
Thermal Conductivity : 0.0245 \(W/mK\)

Boundary Conditions

Each boundary condition is set as follows

inlet : Velocity Inlet
- Velocity Specification Method : Magnitude, Normal to Boundary
- Velocity Profile Type : Temporal Distribution
  - piecewise linear : (0, 1) (0.1 2) (0.2 1.5)
- Turbulent Intensity : 1 (%)
- Turbulent Viscosity Ratio : 10
- Temperature Profile Type : Temporal Distribution
  - piecewise linear : (0, 300) (0.1 400) (0.2 350)

outlet : Pressure Outlet
- Total Pressure : 0 (Pa)
upperWall, lowerWall : Wall
- Velocity Condition : No Slip
- Temperature : Adiabatic
frontAndBack : empty

Numerical Conditions

For Numerical Conditions, use default values.

Monitor

Monitor flow rate and temperature at inlet.

Select [Monitors]-[Add]-[Forces] and set values as shown below.

Surface Monitor 1
- Report Type : Mass Flow Rate
- Surface : inlet

Surface Monitor 2
- Report Type : Area-Weighted Average
- Field Variable : Temperature
- Surface : inlet

Initialization

Set velocity, pressure, temperature and turbulence as follows.

Velocity
- X-Velocity : 0 (m/s)
- Y-Velocity : 0 (m/s)
- Z-Velocity : 0 (m/s)
Pressure
- 0 (Pa)
Temperature : 300 (K)
Turbulence
- Scale of Velocity : 1 (m/s)
- Turbulent Intensity : 1 (%)
- Turbulent Viscosity Ratio : 10