Week 1: Channel flow simulation using CONVERGE CFD

Channel Flow Simulation Using Converge-CFD

Aim: To perform a channel flow simulation using Converge and postprocess the result in Para view.

Objective:

• Run 3 simulations and compare the results between all the 3 simulations.
• 3 different base mesh sizes are,

dx = 2e-4m, dy = 2e-4m, dz = 2e-4m
dx = 1.5e-4m, dy = 1.5e-4m, dz = 1.5e-4m
dx = 1.0e-4m, dy = 1.0e-4m, dz = 1.0e-4m

Introduction-

• Channel flow is mainly for the transport of fluid (Liquid or gases) from one place to other place with different cross section area (e.g., square, rectangle etc.) in general channel are long and straight

Application-

• Major in chemical industries, food processing industry, Refrigeration and air conditioning (duct), automobiles

Geometry Creation

• Before setting up the simulation download necessary software’s that are required for simulation and post processing.
• Initially open Converge Studio and create geometry of a Channel. For this go to Geometry - Create - Shape-Box - specify the centre for geometry.
• Next go to Geometry -options -select Surface Normal. After selecting the Surface Normal the normal point towards outside, so select any one arrow that is point outwards and click on them. Then the normal change their direction to inwards.
• After setting the geometry, next important thing is to diagnosis the geometry for errors/problems. For this go to Right Bottom side, select Diagnosis -click on All intersections -click Find. On top we can check for problems in Problem Triangles.
• If there are no errors found then the geometry is correct.
  To we should do Case Setup. Just beside Diagnosis & click on Case Setup After in case setup window we can see 'Begin Case Setup" & then click on it to set the setup.

Some screenshot

Geometry tab – create -shape – box /centre

(0.05 , 0 , 0) && (0.1,0.01,0.01) and apply on create

Click on boundary and Create boundary

Check normal vector

Again geometry- transform-normal/select the any one surface of triangle then click apply to avoid fatal error go to transform-rotate-select entire surface- rotate by 90 degree about x-axis then apply

Before proceeding the error in geometry for that

View tab-diagnosis dock-default setting-select the find

Case Setup:

Application Type = Time-based

Materials -

Predefined mixtures = Air

Select ‘Gas Simulation' & 'Species (not in mech.dat)'

Click on Species > select Gas > click on Add and select N2 &O2.

Simulation Parameters-

In Run Parameters two main things to be considered: -

select the following solver settings.

Go to Misc. > uncheck UseSharedMemory and click on Steady-State Monitor.

Steady-State Monitor:

Simulation Time Parameters: -

Solver Parameters [Steady-State]-

Boundary Conditions-

Boundary:

Inlet

Outlet

Top Bottom -Wall

Forfront2D and bacK2D > Boundary type: TWO_D

Initial Conditions and Events: -

Regions and Initialization:

Physical Models: -

• Uncheck Turbulence Modelling in this case

Grid Control: -

Base Grid:

• case-1 dx = 2e-4m, dy = 2e-4m, dz = 2e-4m
• case-2 dx = 1.5e-4m, dy = 1.5e-4m, dz = 1.5e-4m
• case-3 dx = 1.0e-4m, dy = 1.0e-4m, dz = 1.0e-4m

Note: change base grid size according to your setup

Post-Processing: -

Post Variable Selection:

Click on Typical Variables/Geometry > Select required variables.

Click on Species/Passive

Output Files:

Note: check green tick mark on each option in case setup

• With this setting up of the case is completed.
• Now go to File > Export > click on Export Input Files.
• select the destination folder (channel test) to save the data.

Note: If any file is skipped then error should be occur (total 10 files)

• Solving: (solver for converge & executable for Cygwin64)
• compulsory copy the two executables (converge.exe & mpi.exe)
• copy the converge.exe from “c/programfiles/convergent_science/converge/3.0.16/bin/intelmpi/converge.exe" paste into case set-up folder (where simulation take place).
• copy the mpi.exe from "c/programfiles/convergent_science/converge/3.0.16/bin/mpi/intel64/bin/mpiexe.exe" paste into case set-up folder (where simulation take place).

How to covert the simulation file in order to support paraview

I am follow skill lync knownlege-base section

link for this knownledge base file-

https://skill-lync.com/knowledgebase/how-to-post-convert-3-d-output-data-in-converge-v3-0

Results.

Case-1

Mesh sizes - [dx = 2e-4m,dy = 2e-4m,dz = 2e-4m]

Velocity Contour:

Pressure Contour:

Velocity Profile at 0.05m from inlet

Mass Flow Rate Plot at Inlet

Velocity At Inlet

Pressure At Inlet

Mass Flow Rate Plot at Outlet

Velocity At Outlet

Pressure At Outlet

Total cells:

Total cells=25000

Animation Link:https://www.youtube.com/watch?v=hfvvwi_ikXg

Case-2
Mesh sizes - [dx = 1.5e-4m, dy = 1.5e-4m, dz = 1.5e-4m]

Velocity Contour:

Pressure Contour:

Velocity Profile at 0.05m from inlet

Mass Flow Rate Plot at Inlet

Velocity At Inlet

Pressure At Inlet

Mass Flow Rate Plot at Outlet

Velocity At Outlet

Pressure At Outlet

Total Cells:

Total cells=45000

Animation link:https://www.youtube.com/watch?v=eW67wnfepuA

Case-3

Mesh sizes - [dx = 1.0e-4m, dy = 1.0e-4m, dz = 1.0e-4m]

Velocity Contour:

Pressure Contour:

Velocity Profile at 0.05m from inlet

Mass Flow Rate Plot at Inlet

Velocity At Inlet

Pressure At Inlet

Mass Flow Rate Plot at Outlet

Velocity At Outlet

Pressure At Outlet

Total Cells:

Total cells=100000

Animation link:https://www.youtube.com/watch?v=Bmda43mCNac

Conclusion

• From the simulations performed it is clear that, for mesh size (2e-4, 1.5e-4, 1.0e-4) the total cell count for each of the mesh are 25000, 45000, 100000 respectively. Hence as the mesh becomes more finer and finer the total cell count increases, as the cell count increases the computational time also increases.
• It is observed that, velocity in the initial case is highest but as the mesh is coarse it is generally not preferred to be accurate. In the next two cases it calculated more accurately.
• The pressure obtained in all the cases remains constant. This is because both inlet and outlet are provided with constrained boundary conditions.
• Mass Flow Rate at the outlets for the refined cases are almost same. When both inlets and outlets are compared, we can observe a positive flow and a negative flow.
• Hence, as the grid size increases the results obtained are much clear and accurate.
• The channel flow simulation using Converge CFD is performed. With different mesh sizes the accurate results are obtained.
• Various plots, contours, profiles, animations are generated in order get the clear understanding of how the flow is inside a channel with the help of Converge CFD software.