# compressible flow in CFX!

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 January 12, 2008, 19:20 compressible flow in CFX! #1 Ihsan Guest   Posts: n/a Hi guys I am new to CFX! Can we simulate a compressible flow in CFX with lower velocity. Fluent had an option where we could specify whether we want our flow to be compressible or incompressible. Is there such option in CFX? How can we simulate a compressible flow in CFX? Thanks in advance for your answer!

 January 13, 2008, 00:29 Re: compressible flow in CFX! #2 Jia Li Guest   Posts: n/a As I know, two things shall be concerned: 1. The material must be density changeable, such as "Ideal Gas" 2. If you model heat transfer, "Total Energy" option should be select. You can refer the help documents at : ANSYS CFX-Solver Modeling Guide | Basic Capabilities Modeling | Physical Models |

 January 13, 2008, 03:27 Re: compressible flow in CFX! #3 Jack Guest   Posts: n/a If you choose Ideal Gas Air as your fluid, it will be a compressible simulation.

 January 13, 2008, 11:57 Re: compressible flow in CFX! #4 Mann Guest   Posts: n/a I am interested in Simulating acoustic (sound) in CFX with LES. For that my simulation will have to be compressible. Is it possible to do that in CFX. If yes how? Thanks in advance

 January 13, 2008, 18:42 Re: compressible flow in CFX! #5 Jack Guest   Posts: n/a Hi! Mann, I think so, although I never done it before. CFX is a very powerful package. Please tell me how to do that when you find out. Thanks

 January 14, 2008, 05:43 Re: compressible flow in CFX! #6 Mann Guest   Posts: n/a Ok no worroies Jack! Mann

 January 14, 2008, 16:35 Re: compressible flow in CFX! #7 Glenn Horrocks Guest   Posts: n/a Hi, CFX definitely can model sound (acoustic) waves in air, I have done it many times. CFX solves the full viscous compressible navier stokes equations but for most acoustic applications a far simpler equation set without viscosity and a reduced linear wave model works well, and therefore CFX is overkill. What are you trying to achieve with acoustic modelling? What type of acoustics is it? I should point out that the acoustics work I did had pressure waves of sufficient magnitude that the waves are no longer linear so the simple assumptions of general acoustic software was not applicable. Glenn Horrocks

 January 14, 2008, 16:57 Re: compressible flow in CFX! #8 Mann Guest   Posts: n/a Hi Glenn My supervisor has asked me to look into acoustic and LES. We are interested in simulating some sort of acoustic with LES. Thats why he asked me to investigate if it will be possible with CFX. Can i ask what type of acoustic work did you do and what code did you use for it. Can you send me any of the work that you did or some other relevant information. Thank you

 January 15, 2008, 16:56 Re: compressible flow in CFX! #9 Glenn Horrocks Guest   Posts: n/a Hi, My PhD work was modelling an internal combustion engine and an important part of that is the pressure waves in the manifolds. You can see my thesis on the web at http://hdl.handle.net/2100/248 Yes, CFX can do acoustics and LES. Whether what you are trying to do can be done on anything smaller than a supercomputer and several years computational time will depend on what you are trying to model. Glenn Horrocks

 January 15, 2008, 18:50 Re: compressible flow in CFX! #10 Mann Guest   Posts: n/a Ok Thanks for the link Glenn. I will look into it! I will get back to you if i need to ask you something else. I hope you wont mind! Mann