Pipe flow

John Grimm

This problem may seem very trivial to many of you, but any help would be greatly appreciated. I am trying to model the movement of water in a straight pipe, but I am a little confused about the modelling of the near wall region. I have been forced to use wall functions against the advice of a previous posting due to lack of computer resources. In the Fluent Manual a y+ value of between 30 and 60 is recommended. For my case this has a non-trivial effect on the velocity profile close to the wall and I am unsure which flow field is 'most accurate'. Are there any more specific guidelines for the values of y+ for a pipe?

I am also interested in validation approaches. I have compared my velocity profiles with theoretical profiles and they match quite well. I was recommended to use the Hinze book to look at turbulence data, but I am trying to get my head around how to use the data and if it is appropriate to validate water flow with air flow measurements. Does anybody know if it is OK to do this (I have been told that when non-dimensionalised turbulence comparisons are the same for air and water) and if any data is available where turbulence has been measured in water flowing through a circular pipe.

Also can anyone recommend further validation approaches?

Thanks in advance for spending the time to answer my question, John