Week 3: Flow over a backward facing step

Week 3: Flow over a backward-facing step

Once you have watched the video, setup the case in CONVERGE

Once you have the base setup ready, run the case for three different base mesh sizes

• dx = dy = dz =2e-3m
• dx = dy = dz =1.5e-3m
• dx = dy = dz =1.0e-3m (If this is too much for your PC, use 1.2e-3m)

Post process your results and document your findings in https://projects.skill-lync.com/

Contents to be shown in the report:

1. Show the mesh (i.e surface with edges) for all the 3 base mesh sizes

2.Show pressure and velocity contours

3. Show the plots of velocity, pressure, mass flow rate and total cell count for all the 3 base mesh sizes

4. Also explain where and why separation is taking place in detail.

Make sure you make your project public. Once you are done, paste the link to your project here.

Create animations and upload on Youtube and provide the youtube link in the report.

Download the geometry attached here

Answer

This is a simple geometry for the analysis of a fluid through a backward-facing step.

Firstly, we need to scale down the geometry as its a big so simulation time will be huge, so we re-scaled to 0.001.

Boundary condition

Make the Gas simulation as Default

Global Transport Parameters - make it default

reaction mechanicsm

Simulation time parameter

Solver Parameter

Regions and Initializations

Turbulemce Modelling

Case I

• dx = dy = dz =2e-3m

Base Grid

Boundary Conditions

Now we need to run the simulation using Cygwin using the commands

We use converge to convert the files to paraview readeble files

In paraview the .vtm files is opened and click apply

the CAD in paraview

the velocity contour

The Pressure contour

Line plot showing mass flow rate

Total Cell Count

Average velocity at outlet

Static Pressure at Boundary

************************************************Case 2 *********************************************************

• dx = dy = dz =1.5e-3m

Velocity Magnitude

Pressure

Line graph showing mass flow rate

Average velocity at outlet

Total pressure at outlet

Total Cell count

*********************************************CASE 3 ************************************************************

dx = dy = dz =1.0e-3m

results

velocity

Pressure contour

Velocity at outlet

Pressure At outlet

Mass flow rate at boundary

Total cell count

Also explain where and why separation is taking place in detail.

The separation of the air flow takes place at the point where the area of the cross-section increases, that is at the edge inside the box

thank you