Learning Forum

[zoelle.wong]

I am modelling an ionizing, supercrticial flow. Under "materials", the fluid's thermodynamic properties are being calculated through a UDF and the density is calculated using the Peng Robinson Equation of State. I am using a pressure solver, because my back-of-the-envelope calculations indicate that the maximum speed is M<1.0

Mach number for an ideal, calorically perfect gas is commonly known as the U_infty/sqrt(\gamma R T), where speed of sound, a = sqrt(\gamma R T). But for a real flow, a^2 = \partial p/ \partial \rho |s = \gamma \partial p/ \partial \rho |_T  (image below)

When post-processing my results, I can create a Mach contour plot. But how is ANSYS fluent computing the mach number and speed of sound in the backend? Is it computing the speed of sound as a change of pressure and density for each cell? What kind of numerical schema does it use if it does compute the speed of sound as a function of pressure and denstiy for each cell? When reading through the theory manual, it doesn't provide these kinds of details. Thank you so much in advance! 

[Essence]

Hello,

Yes, Fluent uses the equation as displayed in the image to determine speed of sound for real fluids.