Hello, I simulate a transsonic, compressible air compressor and have some problems in postprocessing my results. If I try to visualize Mach Number, I can't find the variable Mach Number. In addition, the compressor efficienices don't appear in the Turbo Report. Maybe anybody is able to give me a tip to solve even one of those problems.

Thanks Tobias.

hello, i am also analysing the transonic compressible flow using a centrifugal compressor. I think you have to use equation to find the efficiency of the compressor. refer to 'fans' bruno eck (since you know how much air is pressurised, slip factor, inlet temp, power input factor) Hope this helps^^ oh... can i ask you one question? how did you set the boundary condition of inlet and outlet? cause compressible flow only allows pressure in and pressure out...that means right assumption of pressure out is required? or could you tell me the technique on analysing compressible flow in fluent? thanks

Hello, thank you for that tip, I'll try it. Maybe I can give you some advises. I use a pressure inlet and pressure outlet. One intention of my simulation is to calculate the characteristic line (total pressure ratio over machine massflow). That's why I have to assum diferent average outlet pressures as an variable to controll my simulation on different operation points( operation point with specific total pressure ratio and specific massflow).

The technique to analyse compressible flow is well explained under fluentusers.com - there is a report about convergence strategies under 'recent users meetings' -> 2005 and although a report about steady and unsteady compressible flow.

Hope this although helps, Tobias.

And thanks to Riaan

hello, Tobias

Thank you for an advise. I went into the user website. I still have one question from you.. If you assume pressure inlet and pressure outlet, what about rotational speed of the impeller? cause pressure outlet and rotational are directly proportional. isnt it? so what youe done is let certain rotational speed and vary the outlet pressure? if so, how do you know which outlet pressure is appropriated for certain case? (by backflow?) lookforward to hear a reply, soon. Thank you

hello, gisu park

you assumed right. In my simulation the rotational speed is constant and i only vary the outlet pressure. To find a well posed intervall of outlet pressure values I searched a minimum pressure by calculate the equation: static inlet pressure*(assumed) minimum pressure ratio value (1.1~1.2 axial compressor). Then I increased the outlet pressure in 5000 Pa steps.

I hope this helps, Tobias.

thanks Tobias. It really helped alot~ since we are all working on the compressor simulation, lets keep in contact~ but it seems like you know much more than me ^^ bye

Ok, I guess this post won't be on this site for a long time so just write me a email o tfroebel@gmx.de.

Tobias