Converge CFD

Shock Tube simulation using Converge CFD

OBJECTIVE-Setup a transient shock tube simulation and plot the pressure and temperature history in the entire domain.Also plot the cell count as a function of time.

Geometry-A 3d geometry of shock tube was imported to converge studio.

Setup-

Applications-

-General flow

Materials-

-Air

Simulation Parameters:

-Transient state solver

-Start time-0, End time-0.003 s

-Intial time step=minimum time step=1e-9 s

-Maximum time step=1 s

Boundary conditions-

-High pressure walls-WALL-Slip ,Temperature-300k

-Low pressure walls-WALL-Slip ,Temperature-300k

-Front- 2D(high pressure and low pressure)

-Back – 2D(high pressure and low pressure)

Regions & Initialization:

Boundaries are assigned to region

Region_0-High pressure region

-Pressure=600000 pa

-Species=N2

Region_1-Low pressure region

-Pressure=101325 pa

-Species=O2

Events:

Base grid- dx=dy=dz=0.001 m

Adaptive mesh Refinement:

Spcies-N2, Type-permanent, SGS embed-0.01

Mesh-

Total cell count:

Due to adaptive mesh refinement it can be seen that the cells are changing with time.We can see that after the diaphragm has ruputured at 0.001 s the mesh size starts changing.The refinement of cells are done according to SGS criteria.

 

Pressure plot at high pressure and low pressure region:

The below graph shows the pressure variation at high pressure and low pressure region.

We can see that the pressure at both regions are constant till 0.001 seconds.As the diaprhgm breaks after 0.01 seconds, N2 from high pressure region pushes towards O2 at low pressure.

There is decrease in pressure in high pressure region and increase in pressure in low pressure region.

And the pressure changes accordingly when the shock front is reflected back.

Temperature plot:

After rupturing of diaphrgm N2 from high pressure region produces a shock and passes to the low pressure O2 region.

So the temperature at low pressure region increases and decreases at the high pressure region.And after the shock is reflected back the temperarure at low pressure region increases and at high pressure region decreases.Changes in temperature is seen with to and fro movement of shock front.

 

Animation:

Mass fraction of N2 across the tube:

After rupturing of diaphrgm N2 from high pressure region produces a shock and passes to the low pressure O2 region.

 

Velocity variation:

Conclusion:

1. A transient shock tube simulation was performed.

2. Pressure and temperature history in the entire domain was generated and studied.

3. From the plot for cell count as a function of time, AMR phenomenon was studied.

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