Week 1: Channel flow simulation using CONVERGE CFD

GEOMETRY SETUP:

Go to geometry editing toolbox>create>shape>box here we can enter the value of center and dimensions of dx,dy,dz to create the geometry.

After that in the geometry toolbaox slect boundary>flag>slect ion. as new window nameb boundary will appear and create the number of boundaries we require and click apply. assign the boundaries to the 6 faces of the channel and rename the boundaries as inlet ,outlet, top_bottom_wall,front_2d,back_2d.

after that check the orientation of normal by clecking the ormal toggle icon which is located bottom side in left panel. the normal should be pointed towards the flow of fluid or air in the channel but here the normals are pointed reverse as shown in the below.

to reverse it select any traingle pointed away from the flow and select transform in the geometry toolbox>normal>click on propagate change from single triangle and press apply.

after that run the diagnosis for the geometry to check the errors. if all the parameters are having a green tick mark then there are no errors in the geometry.

The case set up:

slect application type>time-based>apply.

Materials:

1 Gas simulation:

2 Global transport properties:

3 species:

SIMULATION PARAMETERS:

Here turn of the shared memory in misc.

STEADY STATE MONITOR:

SIMULATION TIME PARAMETER:

SOLVER PARAMETER SEADY STATE:

BOUNDARY:

INLET:

OUTLET:

TOP_BOTTOM_WALL

FRONT_2D & BACK_2D

REGION AND INITILIZATION:

PHYSICAL MODELS:

Disable the tirbulence modeling then select apply:

GRID CONTROL:

For the meshing we have to mention the values of dx,dy,dz in the grid size and then ok. Here we have 3 different mesh grid size as 2e-4 ,1.5e-4 , 1.0e-4

OUTPUT AND POST-PROCESSING:

POST VARIABLE SEECTION:

OUT PUT FILES:

After all check the validation  the green tickmark is there in all and no error is shown :

EXPORT ALL INPUT FILES INTO A FLODER:

After exporting the files copy mpiexec.exe file and converge file to the folder in which the input files are exported:

after to simulation open cygwin:

open cygwin navigate to the folder in which the input files are exported and run the command as mpiexec.exe -n 4 converge.exe restricted then press enter the simulation will run automaticaly.

* Post convert all the output files:

i have convert the output files in converge studio on the bottom left side select the last icon to post convert the output files. enter the case name as test and select file type as paraview VTK in-line binary format. in the directory select the output folder and copy the location and paste in the directory> select all in files and cell variables>convert.

* post processing the files:

lanch paraview and open it then open file location as casel..vtm this is the group file which formed during the post converging the files and after that click apply.

RESULTS:

FOR dx=dy=dz=2e-4:

Pressure and velocity countour:

mass flow rate plot:

pressure plot:

average velocity:

total cell count:

for dx=dy=dz=1.5e-4:

pressure and velocity coutour:

mass flow rate plot:

pressure plot:

average velocity plot:

total cell :

for dx=dy=dz=1.0e-4:

 pressure and velocity coutour:

mass flow rate plot:

pressure plot:

 average velocity plot:

 total cell :

animation link:

https://youtu.be/0unogpkfq9U

 conclusion:

*If the grid size decreases then the total cell count increases and the simulation time also increases then we can get accurate results and smooth plots.

*if the mesh size decreases the converge decreases the time step to maintain the CFL number.