Flow over a backward facing step using CONVERGE CFD

Title: Flow over a backward facing step using CONVERGE CFD

Objective: 1. Make setup for backword facing step

                  2. To run the simulation for three diffrent mesh size 2e-3, 1.5e-3, 1.2e-3

                  3. Plot the velocity, pressure, mass flow rate, total cell count

Theory:

In this challenge consider a backword facing step & through this there is supply air. in this challenge its very important to observe the how pressure & velocity changes at backword step. there is use of diffrent three mesh 2e-3, 1.5e-3 & 1e-3.

step for Setup the challenge in CONVERGE STUDIO 

Case setup

1. Fluid used -Air

2. Solver- Pressure based

3. end time -15000cycle

4. Intial & minimum step =1e-6

5. Maximum time step= 1

6. Inlet pressure= 110325pa

7.outlet pressure=101325pa

7. Grid size = 2e-3, 1.5e-3, 1e-3

1. Geometery creation 

2 Run parameter setup

3. Run cycle

4. Solver parameter

5.Boundry ID

6.Region creation 

7. Turbulence model

8. Mesh size

9. Fixed embedding

Fixed embedding its used for refine the mesh for perticular area. in this case top & bottom where we have to refine the mesh. 

CASE 1: 2e-3 

Mesh 

Velocity contour

Pressure contour

Vector plot

Observed recirculation zone at backword step & its created due to suddent expansion in area & reduction of static pressure

CASE2: 1.5e-3

Mesh

Velocity contour

Pressure contour

Vector plot

Observed recirculation zone at backword step & its created due to suddent expansion in area & reduction of static pressure

CASE 3: 1e-3

Mesh

Velocity contour

Pressure contour

Vector plot

Observed recirculation zone at backword step & its created due to suddent expansion in area & reduction of static pressure

Output Result

1. Mass flow rate 

from below plot verify the continuity equation i.e INFLOW=OUTFLOW. maximum mass flow rate is 1kg/s

2.Aveg. Velocity

from below plot verify the continuity equation i.e INFLOW=OUTFLOW. maximum Aveg velocity 40m/s

3. Static Pressure 

for refined mesh static pressure is accurately capture it 

4. Total cell count 

more refined mesh 1e-3 acquire more cell around 5500cell

Animation Video for 1e-3 Mesh 

Velocity animation 

Pressure animation 

Flow sepration at backword facing step because

1. Sudden expansion at backward step

2. loss of momentum at backward step

3. reduction of static pressure creates recirculation zone

Overall conclusion

1. Observed as mesh size decreases simulation time increases & result more accurate

2. Verify the continuity equation by plot of velocity, mass flow rate parameters.

3. Flow sepration observed near the backword step due to expansion in area & reduction of static pressure.