Phil Dias Shock Tube
Introduction:
This project sets up a transient shock tube simulation using Converge CFD. The simulation studies pressure, velocity, and temperature during the collision of high pressure Nitrogen and low pressure Oxygen. Geometry is imported, boundaries are flagged, and regions are established. A base mesh grid of dx=dy=dz= 0.001m is used. Adaptive mesh grid species sub-grid scale conditions are set to SGS=0.001. Post processing results are displayed on ParaView.
Inputs:
Two regions represent high and low pressure areas in the shock tube. High pressure is green and low pressure is brown.
High Pressure Region (N2) = 600000 Pa
Low Pressure Region (O2) = 101325 Pa
Regions:
Two regions are used to separature the two gases. Region 0 contains high pressure N2 while Region 1 contains atmospheric pressure O2. Events are used initially disconnect the two regions, them connect the two regions to simulate the popping of the diaphragm in the shock tube. This event takes place at 1ms.
Grid Control:
A 1mm grid size is used in the x-direction. A species AMR is defined for Nitrogen (N2) with a SGS value of 0.001.
Results:
AMR parameters dictate the cell count causing variation in cell count over time. Cell count is constant until the diaphragm is \"popped\" at 0.001s. A wave effect occurs at 0.001s. As the wave travels, the N2 concentration ondulates accordingly. This wave motion and mixing of the two gases are responsible for the variance in cell count.
AMR Animation:
Velocity Animation:
When the diaphragm is \"popped\" at 0.001s, the high pressure N2 expands into the low pressure region. The transfer of energy is observed to fall with each back and forth cycle, until it eventually reaches homeostasis.
Pressure Animation:
Temperature is observed to rise and fall due to compression and expansion of the mixing fluids. Change in temperature is only observed after the diaphragm is popped.
Temperature Animation:
Conclusion:
This project observes the mixing of high pressure Nitrogen (N2) and low pressure Oxygen (O2) in a shock tube. AMR is used to refine the results. When the diaphragm is \"popped\" and the gasses are allowed to mix, concentration, pressure, velocity, and temperature are observed.