Hi I am dealing in a medium that is compressible at subsonic speeds using the dubroutine densit. The compressibility is dictated purely by pressure and not by temperature denisty=logarithmic function of pressure plus reference density if you know what i mean. I have programmed DENP as the above relationship and DENS as DENREF+DENP, is this right? i am getting an error at the begining of my simulation that densit is activated but not used, is this because the flow is subsonic or is my programming wrong, also it says that DENP is not defined but this is after the initial error and i pressume is due to the densit not being used. Any ideas? Cheers Joel

Hi Joel,

If it says a subroutine is activated but not used, it generally means that you haven't linked the coding in. Check that in your working directory there is a subdirectory called "ufile", that your coding is in there and stored as a file called densit.f.

Next, run starlink and answer "yes" to the question relating to user coding. starlink should then tell you that it has compiled densit.f.

Then run it again. Seeya.

cheers, for that it was just me being stupid in the end and not flicking the right switch as it were. Having got the subroutine itself working i am having trouble with the simulation. I think there is a problem with dendp i am not entirely sure what Dendp and den should be. As i said before my density is directly related to pressure alone by logathmic relationship. Is this relationship Den and if so what is DENP supposed to be