Home / Examples / Fluid Analysis [Bernoulli] / Example 19: Convection Caused by Generation of Impurity Substance

Example 19: Convection Caused by Generation of Impurity Substance

General

• The diffusion analysis with the weight of the diffusing materials taken into account is applied for the convection caused by an impurity substance generated in a closed space.
   

• The resulting convection and concentration distribution are compared between cases where the diffusing material is water vapor (H2O), which is lighter than air, and cases where it is sulfur dioxide (SO2), which is heavier.
  

• The flow velocity distribution, the flow velocity vectors, and the impurity substance concentration distribution are solved.
   

• Unless specified in the list below, the default conditions are applied.

 

• Obtain this session's project file. (Right-click and choose 'Save link as')

• 
  

• Results will vary depending on Femtet version and the PC environment.

 

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

 

Analysis Conditions

Item	Tab	Settings
Solver	Solver Selection	Fluid Analysis [Bernoulli]
Analysis Type	Fluid Analysis	Transient Analysis
Timestep	Transient Analysis	Timestep: Specify   No. Number of Calculation Steps Output Interval Timestep [s] 1 20 1 1
Diffusion Analysis	Fluid Analysis	Select Diffusion Analysis
Diffusion Analysis Setting	Fluid Analysis	Analysis Type: Transient Analysis Type and Unit of Diffusion Quantity: Molar Concentration [mol/m3] Select [Take into account weight of diffusing materials].   Diffusing Material Setting: Analysis Model Settings H2O-Wall Select [300_Water Vapor H2O] from the material DB and click [Input]. SO2-Wall Select [314_Sulfur Dioxide SO2] from the material DB and click [Input].
Meshing Setup	Mesh	General Mesh Size: 10 [mm]

Model

 

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	Air	000_Air *
1/Solid	Plate	001_Alumina *

* Available from the material DB

 

Boundary Conditions

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
Ground/Face	Fluid	Solid Wall
Source/Face	Fluid	Solid Wall	Diffusion Analysis Setting Select Flux Molar Concentration Flux: 0.01 [mol/m2/s]
Outer Boundary Condition	Fluid	Solid Wall

 

Results

The flow velocity vectors on the section at y=0 at 20 [s] are shown below.

When water vapor, which is lighter than air, is generated on the top of Plate, an upward flow occurs.

When sulfur dioxide, which is heavier than air, is generated on the top of Plate, a downward flow occurs.

 

H2O-Wall	SO2-Wall

 

 

The contours of molar concentration on the section at y=2 at 5 [s], 10 [s] , and 20 [s] are shown below.

If the impurity substance is water vapor, the substance stays at the top of the closed space, and if sulfur dioxide, stays at the bottom.

 

Time	H2O-Wall	SO2-Wall
5 [s]
10 [s]
20 [s]