[lofty]

Hi Guys

I am very new to OpenFOAM. I hope you wont mind me asking you following questions.

1. Where do I specify a source term for pressure to sustain my flow with channelOodles solver.
2. How can I write rms and mean values for my variables in OpenFOAM.
3. Can I use solution from a RANS model in OpenFOAM to initialise fluctuations.

Thanks in advance for your help.

[alberto]

Hello and welcome!

1. channelOodles does not require you specify a pressure gradient, but the mass flow rate (Ubar). If you want to introduce a constant pressure gradient you have to modify the code.

2. postChannel does that.

3. Yes, you can. But it's better you use something more sophisticated if you want turbulence to develop in a reasonable time. There's a tool to initialize a channel flow: look for it in the forum.

Regards,
Alberto

[lofty]

Thank you very much Alberto.

1. Can some one tell me please what is relationship between friction Reynolds number (Re tau) and mass flow rate (Ubar).

2. Where do I place PerturbU.tgz and how do I get to compile it and subsequently get OpenFoam to recognise it.

I know I am asking for too much. Even if you can direct me to relevant literature (if there is any)it will very helpful. Thanks in advance.

OpenFOAM Newbie

[johndeas]

There is no such relation. Re tau is defined by u_tau, not u_bar, and you have to calculate your flow to find u_tau, or find a correlation for your specific configuration. Take a look at the wiki at cfd online.

[lofty]

Thank you John. I can calculate U tau, but that would only give me friction velocity. How can I obtain mass flow rate from it? Paraview has no option to calculate mass flow rate which is quite strange.

Can anyone please tell me please where am I suppose to place PerturbU.tgz and how do I get FoamX to recognise it. Thank you

[cedric_duprat]

Hi " OF Newbie"

let's start by the perturbU. because it is to preProcess your run, I suggest you to put it in applications/utilities/preProcessing
then, instal the package, compile it. I should works.

but you know ... FoamX will not recognise it. so to use it, you will have to do something like that: perturbU <root> <case> as usual.
In fact, FoamX can do the "minimum" if you want more, it's not usefull anymore.

Should I say more about perturbU ?

for your friction velocity and your mass flow, ...
I think you want to understand the source term in channelOodles, don't you ?
If so, let's have a look there :
http://www.cfd-online.com/OpenFOAM_D...html#POST14146
It's a discution between Hadi Tartoussi and Henry Weller

I hope it helps,

Cedric