# R used in thermodynamicproperties

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 June 13, 2008, 10:33 Hi I find that R is set to #1 Member   srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 90 Rep Power: 8 Hi I find that R is set to .714286J/(KgK), in most of the examples. This does not correspond to specific gas constant of air. So is foam assuming some strange gas for the examples or am i missing something? Univeral gas constant = 8.314J/(mol K) Mol wt of air =29gm/mol Therefore specific gas constant = 8.314/.029 = 287 J/(Kg K)--Also confirmed by wikipedia Am i missing something trivial here? Could someone please clear this, as i am trying to benchmark the solvers? Regards Srinath

 June 13, 2008, 11:26 Can you please list out the tu #2 New Member   Arun Shourie Join Date: Mar 2009 Location: Singapore Posts: 12 Rep Power: 8 Can you please list out the tutorials. But in sonicFoam tutorial its given correctly only

 June 13, 2008, 12:29 The value of R, i find in #3 Member   srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 90 Rep Power: 8 The value of R, i find in /tutorial/sonicFoam/forwardstep/constant/thermodynamicProperties is as follows R [0 2 -2 -1 0 0 0] 0.714286; But i do notice that it is set to 287 in the shockTube directory.--Strange Regards Srinath

 June 16, 2008, 03:47 Hi If you look in the Progr #4 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,606 Rep Power: 25 Hi If you look in the Programmers Guide pp 61, you will find that R is set, such that the speed of sound in air is 1 m/s. Best regards, Niels __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

 June 16, 2008, 06:41 Thanks Niels I also find in #5 Member   srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 90 Rep Power: 8 Thanks Niels I also find in the Programmers guide a reference to thermal conductivity kappa. But nowhere in the code for sonicFoam is kappa even used. It is also not mentioned in thermodynamicProperties in ver-1.4.1 Is this a minor oversight, which can be fixed trivially, by changing mu in the energy equation to kappa? Regards Srinath

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