P*dV Work

bertozzi_marco · August 22, 2013, 13:44

Hallo Everybody,
I have a simple closed volume that expand with pressure variation,
There is a transient analisys, and I'd like to calculate the total work
at the end of the exapnsion,

So normally I will add every P*dv at every step, but I'm not able
to create an expression to do so, It's possible to obtain the value
of the pressure and the volume at every step, but dv should be the
variation Volume(t+dt) - Volume(t) and I don't know how to do this.

any advice ?

Thanks

ghorrocks · August 22, 2013, 18:56

You cannot access values at previous time steps in CFX easily. There are some work-arounds which can (sort of) do it - search the forum to find them.

For this type of work I would output the pressure and volume as a monitor point and do the work calculation as post processing in excel, matlab or whatever you like.

August 22, 2013, 13:44	*PdV Work**	#1
bertozzi_marco Member Marco Join Date: Jul 2013 Location: Italy Posts: 36 Rep Power: 12	Hallo Everybody, I have a simple closed volume that expand with pressure variation, There is a transient analisys, and I'd like to calculate the total work at the end of the exapnsion, So normally I will add every P*dv at every step, but I'm not able to create an expression to do so, It's possible to obtain the value of the pressure and the volume at every step, but dv should be the variation Volume(t+dt) - Volume(t) and I don't know how to do this. any advice ? Thanks

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August 22, 2013, 18:56		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You cannot access values at previous time steps in CFX easily. There are some work-arounds which can (sort of) do it - search the forum to find them. For this type of work I would output the pressure and volume as a monitor point and do the work calculation as post processing in excel, matlab or whatever you like.