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Hello CFD community,

This is my first time posting here, and I am looking forward to receiving some valuable suggestions.

I am currently simulating hydrogen combustion for supersonic flows at Mach 2.44. The simulation domain is 100mm long and 110mm high. I am encountering high residuals, particularly in energy (10^4), x-momentum (10^2), and y-momentum (10), while the continuity residual is below 10^-5, and all other residuals are within acceptable limits. Although the mass imbalance shows oscillations within ±0.1, the combustion efficiency and total pressure plots indicate convergence with seemingly zero oscillations.

Initially, I used a mesh with 42.5k elements and a base element size of 4mm. To reduce oscillations in the residuals, I refined the mesh to a base element size of 1mm, resulting in a total element count of 308k. However, instead of reducing the oscillations, the refinement increased them, especially in terms of combustion efficiency, total pressure, and mass imbalance. These oscillations appear to be very non-physical. I am wondering if the issue might be due to the large jump in mesh refinement.

Can anyone help me understand what might be going wrong in my simulation? Any assistance would be greatly appreciated.

Thank you!