Shock Tube

Aim:

To set up a transient shock tube simulation with nitrogen and oxygen as the two species and post process the results.

Theory:

The shock tube is an instrument used to replicate and direct blast waves at a sensor or a model in order to simulate actual explosions and their effects, usually on a smaller scale. They can also be used to study chemical kinetics, to study aerodynamic flow under a wide range of temperatures and pressures that are difficult to obtain in other types of testing facilities. Investigation on compressible flow phenomena and gas phase combustion reactions can also be studied.

The shock wave inside the shock tube is generated by the build up of pressure due to the presence of a diaphragm. This diaphragm also acts as a separator for the gases inside the tube. Nitrogen is used in the high pressure region and oxygen in the low pressure region. As the pressure increases, the diaphragm gives way and the two gases come in contact and hence shockwaves are generated.The shock tube experiment is useful in studying ignition delay ,pre ignition and the combustion characteristics when fuel and air are introduced as the mediums.

Fig 1: Surface with edges with a base grid of 0.0004

Fig 2: The arrows indicate the direction of flow of the two gases

Graph 1: Variation of the cells in each time step

Vid 1: Animation of pressure

Vid 2: Animation of temperature

Vid 3: Animation of velocity

Conclusion:

By setting up the shock tube simulation, we can get a detailed idea of how flow occurs between two species with respect to variuos parameters like velocity, pressure and temperature.