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Species transport

Mixing in duct

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Introduction

This is an example of an transient chemical species mixing. A two-dimensional duct with two openings is introduced with air at the top opening and water vapor at the bottom opening.

The simulation conditions are as follows

  • solver : buoyantPimpleNFoam
  • turbulence model : \(Standard\) \(k-\epsilon\) model
  • flow condition : 0.5 \(m/s\) at inlet

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.

Set Gravity as (0 -9.81 0).

(Models

Double click Species and select [Include].

Materials

Click the (+) in the top right corner of the Materials panel to add a mixture. Select air and waterVapor as shown on the left in the image below and click 'Create Mixture' to create a mixture as shown on the right.


Cell zone Conditions

Double-click region0 in Cell Zone Conditions and change the Material to mixture.


Boundary Conditions

Set the boundary type and values as shown below.

  • in-up : Velocity Inlet
    • Velocity Specification Method : Magnitudde, Normal to Boundary
    • Velocity Magnitude : 0.5 (m/s)
    • Turbulent Intensity : 0.1 (%)
    • Turbulent Viscosity Ratio : 1
    • mixture - air : 1
    • mixture - waterVapor : 0
    • Temperature : 300


  • in-down : Velocity Inlet
    • Velocity Specification Method : Magnitudde, Normal to Boundary
    • Velocity Magnitude : 0.5 (m/s)
    • Turbulent Intensity : 0.1 (%)
    • Turbulent Viscosity Ratio : 1
    • mixture - air : 0
    • mixture - waterVapor : 1
    • Temperature : 300


  • out : Pressure Outlet

    • Pressure : 0 (Pa)
  • down_surface, up : wall

    • noSlip
  • zMin, zMax : empty

Numerical Conditions

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

  • Pressure-Velocity Coupling Scheme : SIMPLE

  • Discretization Scheme

    • Time : Second Order Implicit
    • Pressure : Linear
    • Momentum : Second Order Upwind
    • Turbulence : Second Order Upwind
    • Species : Second Order Upwind
  • Under-Relaxation Factors

    • Pressure : 0.3
    • Momentum : 0.7
    • Turbulence : 0.7
    • Species : 1
  • Convergence Criteria : use default values

  • Max Iterations per Time Step : 100

  • Number of Correctors : 2

Initialization

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

  • Velocity : (0.5 0 0)
  • Pressure : 0
  • Scale of Velocity : 0.5
  • Turbulent intensity : 0.1
  • Turbulent viscosity ratio : 1
  • mixture - air : 1
  • mixture - waterVapor : 0


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 : Fixed
  • Time Step Size : 0.001
  • End Time : 20
  • Save Interval : 0.1


Post-processing

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

Change [Coloring] to [waterVapor].