Week 3: Flow over a backward facing step
Aim:
To 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
To Show the mesh (i.e surface with edges) for all the 3 base mesh sizes
To Show pressure and velocity contours
To Show the plots of velocity, pressure, mass flow rate and total cell count for all the 3 base mesh sizes
To Also explain where and why separation is taking place in detail.
Steps followed:
- For the simulation of the flow over a backward facing step,initially the file is downloaded.
- For the converge studio to run simulation the geometry has to be in meters. Initial check is made and confirmed.
- Next moving forward with case setup steps,
- Transform the scale to the entire surface and set the scalar factor uniform with value 0.001.
- Check the normal and make modification by choosing normal.
- Create boundary and flag them.
Case setup:
General flow
predefined mixture-air
Full hydrodynamic-Run paramaters
Solver parameters-pressure based and gas flow solver that is compressible.
Set the boundary conditions
Region and initialization is done
Base grid is set to 3 different case with size 0.001,0.0015,0.002
Under grid control, check the fixed embedding because it helps us refine particular areain domain
Fixed embedding-add entity boundary,choose mode to permanent,scale-1 and embedded layer-1
Declare the boundary conditions individullay for inlet,outlet,front,back and top bottom layers
Assign every boundary to region 0
Once case setup is done,check for errors and debug them
Export the input files
Run the simulation in the cygwin.
Post Processing:
Open paraview
Slice the geometry
uncheck the show plane
Choose z-plane
Velocity,pressure options to be chosen
Choose surface with edges
Time 0-max is set to run
Output:
Initial geometry setup.
Case 1: 2e-3m
Case 2: 1.5e-3m
Case 3:1.0e-3m
Mesh Grid:
Recirculation zone:
Conclusion:
As the fixed embedded layer size is increased, the mesh kept refining. And the velocity pressure contour alomg with mesh for all 3 cases are done and the screenshots for the same is attached.