Shock tube Simulation

Introduction

This project aims to simulate a shock tube problem to enhance our understanding of regions and how events function is used for timing an event such as opening and closing the interaction between regions. 

Case Setup

Transient simulation with species Oxygen and Nitrogen is made to run from 0 seconds to 0.003 seconds. The boundary condition is to be wall and 2-D wall with no input and output. The wall boundary follows the law of wall function. 

Two regions are added, one with atmospheric pressure filled with Oxygen another of High pressure (0.6 Mpa) filled with Nitrogen. The event is set in such a way that at 0 seconds the two regions are disconnected and at 0.001 seconds they are open to interacting.

The mesh is generated with adaptive mesh refinement using species and setting it for Nitrogen. The mesh is shown below.

Basic mesh

Mesh with adaptive mesh refinement

Plots for Pressure, Temperature, and Cell Count 

The plot below shows the pressure for both the regions.

The pressure remains constant at the specified value until 0.001 seconds, after which due to events the regions are opened and pressure changes much more like a function of a sinusoidal wave and approaches convergence.

Temperature plot 

The red line shows the high-pressure region and the blue line shows the low-pressure region. The temperature remains constant till 0.001 seconds after the event high-pressure region drops in temperature because of loss in pressure, on the other hand, the low-pressure region rises in temperature due to gain in pressure. this continues till convergence.

Total Cell-Count

Total cell count increases due to adaptive mesh refinement and varies as the nitrogen gas changes its concentration. this will reach a previous value as the solution reaches equilibrium.

Outcome

The project gives a practice of setting up regions and events. It also gives a practical idea about shock tube and its visualization helps in understanding the mixing process of the gases.