Shock tube simulation using Converge CFD
Aim- To study the flow characteristics of the fluid in a shock tube and see the pressure, velocity contours.
Governing equation- The equation used to solve this case is Navier-Stokes Unsteady equations. It comprises of 5 equations continuity, x-momentum, y-momentum, z-momentum, and energy equation. But for this case, the energy equation is not used since there is no gain or loss of energy and the temperature is constant throughout the simulation.
Objective- The objective of this problem is to simulate transient flow in a shock tube and to check the pressure, velocity contours.
Description- First the geometry to be simulated is imported in Converge Studio and then the geometry is checked for any errors. The geometry is grouped into faces so that respective boundary conditions can be assigned and then the case setup is done. For this project, we will be running a transient simulation with end time 3ms. It is a turbulent flow simulation hence RNG k-epsilon turbulence model is selected. A mesh size of 1e-3m is given throughout the geometry and also species AMR is given with embedding level of 3 and SGS criteria as 0.001.
Material- N2 in high-pressure region and O2 in the low-pressure region.
Boundary Condition- high-pressure bc: Slip wall
low-pressure bc: Slip wall
Initial Condition- high-pressure region: Pressure-600000 Pa and temperature:300K
low-pressure region: Pressure-101325 Pa and temperature:300K
Mesh- Mesh size:1e-3m
Cell count
Results-
Pressure line plot
From the above line plot, we can see the variation in the pressure of the two species when the diaphragm opens after 0.001s.
Temperature line plot
From the above line plot, we can see the variation in temperature of the two species because of the shock effect when the diaphragm opens after 0.001s.
Pressure contour
The above pressure contour plot shows the pressure inside the shock tube, the max pressure is 4e+5 Pa and min pressure is 1.8e+5 Pa.
Velocity contour
The above velocity contour plot shows the velocity inside the shock tube, the max speed is 8.3e+1 m/s and min speed is 2.5e-2 m/s.
Temperature
The above temperature contour plot shows the temperature inside the shock tube, the max temperature is 4.6e+2 K and the min temperature is 2.2e+2 K.
The link to pressure animation is attached below
Conclusion
From the above plots, we can see how the shock in a rectangular tube affects the pressure, velocity, and temperature. We also learned a new feature called Events which will be further used in IC engine CFD simulations.