CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

Questions about thermophysicalPropertiesFile

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   November 14, 2008, 06:34
Default Hello Foamers, i simulated
  #1
New Member
 
Oliver Sommer
Join Date: Mar 2009
Posts: 12
Rep Power: 8
lynx is on a distinguished road
Hello Foamers,

i simulated (tested) the "hot room" tutorial with the "buoyantSimpleFoam" Solver. Now i want to change the fluid. The default one is:

mixture air 1 28.9 1000 0 1.8e-5 0.7

"mixture" is a keyword i read in the "User Guide". Also i read the values n_mol=1, W=28.9, cp=1000, H_f=0; eta=0.000018 and Pr=0.7 are all for air.

When i want to change to water f.e., what i have to do?

Simply change these values to values of water?
Or do i have to change the keyword too? What else for keywords exist?
How many other types (combinations) of this "thermoType" exist and are they listet somewhere? Out of the UserGuide i don't get it.

In General, since version 1.5 of OpenFOAM, where can i find a list which parameters i can set for a specific value. Let's say in "ControlDict" for "writeControl". I know "runTime" and "timeStep". With FoamX in version 1.4.1 there where always a drop down menu with all possible parameters for the selected keyword. The same counts for other things, f.e. like patch types (wall or wallfunctions in "buoyantSimpleFoam"). Or my problem decribed above. The thing with the "thermoType".

I hope you understand my problem. I search for a list where some parameters/ names for different keywords for different things are written, because i don't know all the things which could be entered at them.

for tips i thank you in advance

greetings
Oliver
lynx is offline   Reply With Quote

Old   November 17, 2008, 03:27
Default Hi Oliver, just enter anyth
  #2
Senior Member
 
Markus Rehm
Join Date: Mar 2009
Location: Erlangen (Germany)
Posts: 176
Rep Power: 8
markusrehm is on a distinguished road
Hi Oliver,

just enter anything as a keyword which you are sure can't be a real one. For example type MissPiggy as keyword for mixture. OpenFoam will politely tell you that MissPiggy is no valid mixture and list the available ones.

With the properties I am not sure but I think when you change all relevant physical entries it should work for water, too.

Markus
markusrehm is offline   Reply With Quote

Old   November 17, 2008, 04:57
Default Hi Markus, when i do so, th
  #3
New Member
 
Oliver Sommer
Join Date: Mar 2009
Posts: 12
Rep Power: 8
lynx is on a distinguished road
Hi Markus,

when i do so, then i got just an errormessage, that tells me, that the keyword "mixture" is undefined in my "thermophysicalProperties"-file in the xterm (or whatever it is named in linux).

I browsed a bit through the folders of "OpenFOAM/src/thermophysicalProperties" and saw there for example folders named like "basic", "liquidMixture" and "liquids".
Because a subfolder of "basic" is named "hThermo" i got the question whether i can change the thermoType?

Actually i have this standing in my "thermophysicalProperties"-file:

thermoType hThermo<puremixture<consttransport<speciethermo<hc onstthermo<liquidmixture>>>>>

I replaced, just for testing, the "perfectGas"-parameter to "LiquidMixture". Here Foam told me in an errormessage, that i can use only 3 combinations with ("SutherlandTransport", "hConstThermo" and janafThermo) and listet them.

The Question is: Is there any other type, perhaps declared with an other 1st keyword (f.e. instead of hThermo) or 2nd or 3rd, or..

One other thing are the values for the fluid. I tested a bit and noticed that the value for n (number of moles) does not have any influence on the result of the simulation (velocity f.e.). Is this right?
I only get different results, when i change the dynamic viscosity eta (of course) or the molecular weight W. Can anybody confirm this?
I didn't checked the Prandtl-Number, because i let this constant to my fluid.

thank you in advance
greetings, Oliver
lynx is offline   Reply With Quote

Old   November 17, 2008, 06:17
Default Hi Oliver, list of thermoty
  #4
New Member
 
David Palko
Join Date: Mar 2009
Location: Stockholm
Posts: 17
Rep Power: 8
dpalko is on a distinguished road
Hi Oliver,

list of thermotypes is specified in OpenFOAM/src/thermophysicalModels/basic/basicThermo/basicThermos.C

The actual number of moles doesn't matter as soon as you have only one compound mixture, so your results will not depend on this number. The rest of the properties of course naturally changes your results.

For the equation of state, perfectGas is the only class implemented (which would calculate your density using the ideal gas equation of state). I made some comments about this thing before, but it seems that there is no interest in solving this issue.

Regards,

David
dpalko is offline   Reply With Quote

Old   November 26, 2008, 03:39
Default Hello again, in the last we
  #5
New Member
 
Oliver Sommer
Join Date: Mar 2009
Posts: 12
Rep Power: 8
lynx is on a distinguished road
Hello again,

in the last week i had some time and i tried out different things, but with no success. I noticed that it is no matter whether i set the value for n_moles to 1 or for example 0.001 or 100. The result in postprocessing is the same. Only when i change the value for the molucular weight, i get different results. The viscosity and the Pr number i didn't change (they cause different results too, of course).

Actually i wanted to simulate a little cell filled with a mixture of 30% glycerine and 70% Water. This compound i assume as one pure fluid (liquid), because it is very good to mix in the real experiment. Now i want to see, if Foam yield same results as the experiment has shown. But it didn't. That's why i'm searching for errors in my set up.

My molecular weight is 40.2 kg/kmol and my cell has a volume of 11 mm≥ and my density is 1,078 mg/mm≥.
How have i to enter the values for n_moles and W (molecular weight) in the "thermophysicalProperties"-file?

I assume that:

rho = m / V <-> m = rho * V

with that i get the weight of the glycerin/water fluid which is in my cell, filling it completely.

with

W = m / n <-> n = m / W

i want to calculate the number of moles in my cell. With that i yield a value arround 0.0003. That means, i have 0.0003 moles pieces of glycerin/water in my cell. 1 mol has the weight of 40.2 g. So it seems be okay, because the fluid in my cell weights 11 mg.

When i now enter n=0.0003 and W=40.2 in the file, i thought it would work. But the result from the velocity is total different compared to the experiment. Like i said before i changed at 1st n to the valure of 1 (n=1). But this had no change of the result.

Now i thought foam allways assumes 1 mol of the fluid in the volume and i have to change my wolecular weight so, that it fits the formulas above. I did so, entered the value (W becomes very small of course) and the results went again bad. Compared to the 1st trial they are now much more bad then before.

Does anyone know haw to set up this "thermophysicalProperties"-file correct. Or has anybody an idea where i have done an error?

It would be very nice if you can give me a hint. Thank you in advance..


greetings
Oliver
lynx is offline   Reply With Quote

Old   September 24, 2009, 06:29
Default
  #6
New Member
 
Sanjib Das Sharma
Join Date: May 2009
Posts: 22
Rep Power: 8
sanjibdsharma is on a distinguished road
Hi Markus,

I am new to OpenFoam. Having started with the basics 2 months ago, I am now stuck with modeling of steady-state, liquid-phase, multi-species transport with chemical reaction. Can you provide some input as to how I proceed i.e., which modules should I use.

As far as I understood, I compiled with the following:

simpleFoam solver + basicMixture.H + basicThermo.H + liquidMixture.H + liquid.H + pEqn.H + UEqn.H

I have tried to use YEqn.H, but gave error. How to combine this and proceed ? It will be great if you have any example.

Regards,

Sanjib
sanjibdsharma is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
2 questions Snowshovel CFX 5 January 20, 2007 09:49
Questions concerning VOF CFDtoy Main CFD Forum 10 November 1, 2006 23:28
UDS questions Z FLUENT 1 March 31, 2005 14:54
UDS Questions Y FLUENT 0 March 19, 2005 12:58
Few questions phi FLUENT 0 March 4, 2005 10:23


All times are GMT -4. The time now is 11:14.