[liliana]

I am trying to reproduce a transonic flow in a convergent divergent nozzle. I am using a 2D axisymetric model. It has an inlet Mach flow of 0.239543, pressure of 1 bar, temperature of 288 K. At the outlet, the pressure is 0.83 and the temperature is 300 K. The fluid is a real gas - Redlich-Kwong. The x-dimension is 10 cm, the inlet diameter is 1.7841 cm, the outlet diameter is 1.3820 cm and the throat diameter is 1.1284 cm.

I have created the mesh using Directed Mesh at Star CCM+, so it has only quadrilaterals cells. In x-direction it has 400 elements and in y-direction it has 80 elements. It is the same mesh size used in the paper I am trying to reproduce.

I have the results of the density at the center of the geometry (so at the axis of the axisymetric geometry) from the paper I am using as reference (in yellow at XY plot) and it is quite similar (my results is the blue one at XY plot). However, there is a specific point very very weird. It is market in the picture below. This point is located before the shockwave (which occurs at 7 cm) and it is exactly where the velocity reaches the sound speed (around 340 m/s).

I have already tried plenty of coarse and refined meshes and the weird point is still there.

Does anyone worked with transonic flow before and has any idea of what the problem could be?

Picture: https://drive.google.com/file/d/1X4h...ew?usp=sharing