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

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 Step Size : 0.001
• End Time : 1
• Save Interval(Every) : 0.1

그림 11.9

When the calculation is started, you’ll see a graph of Residuals and Monitor as shown below.

Post-processing

Check the distribution of temperature and velocity over time. Click the paraview button in [External tools] to open paraview.

Change the [Solid Color] at the top to T.

Press [Set Range] to adjust the temperature range to 340 – 350K.

Then click the Play icon at the top to see the temperature change over time.

The figure below shows the temperature distribution at the final moment.