Porous Jump

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Introduction

This is an example of the Porous Jump boundary condition, which can simulate a porous plate or fan inside the computational domain as a thicknessless boundary. The problem is to create a square face inside a hexahedral duct and vary the pressure and velocity using the Porous Jump boundary condition.

The computational conditions are as follows

  • solver : buoyantsimpleNFoam
  • turbulence model : $Standard$ $k-epsilon$ model
  • density : 1.225 $kg/m^3$
  • viscosity : 1.79e-5 $kg/ms$
  • boundary conditions for porous jump
    • Darcy Coefficient : -100
    • Inertial Coefficient : -5
    • porous media in the flow direction : 0.05 m

The porousBafflePressure boundary condition that computes the Porous Jump uses the expression below.

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

For this example, we’ll use default conditions.

Models

For this example, we’ll use $Standard$ $k-epsilon$ model for turbulence.

Materials

Use material properties of air.

Boundary Conditions

Set the boundary type and values as shown below.

  • duct : Wall
    • Velocity Condition : No Slip
  • inlet : Velocity Inlet
    • Velocity Specification Method : Magnitude, Normal to Boundary
    • Profile Type : Constant
    • Velocity Magnitude : 10 (m/s)
    • Turbulent Intensity : 1 (%)
    • Turbulent Viscosity Ratio : 10 (m)

  • outlet : Pressure Outlet
    • Total Pressure : 0 (Pa)

  • plane_master : Porous Jump
    • Coupled Boundary : plane_slave
    • Darcy Coefficient : -100
    • Inertial Coefficient : -5
    • Porous Media Thickness : 0.05

Numerical Conditions

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

  • Pressure-Velocity Coupling Scheme : SIMPLE
  • Discretization Schemes
    • Momentum : Second Order Upwind
    • Turbulence : First Order Upwind
  • Convergence Criteria
    • Pressure : 1e-6
    • Momentum : 0.001
    • Turbulence : 0.001

Initialization

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

  • X-Velocity : 10 (m/s)
  • Pressure : 0 (Pa)
  • Turbulence
    • Scale of Velocity : 10 (m/s)
    • Turbulent Intensity : 1 (%)
    • Turbulent Viscosity Ratio : 10

Run

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

  • Number of Iterations : 1000
  • Save Interval : 1000
  • Data Write Format : Binary
  • Number of Cores : 1

When the calculation is started, you can see the graphs of Residuals as shown below.


Residual plot

Post-processing

Draw the pressure distribution inside the duct.

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

Select the [Slice] icon in the top toolbar and click the [Z Normal] button.

Change [Solid Color] to p_rgh.