CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM

therm.dat NASA polynomials

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 9, 2010, 08:15
Question therm.dat NASA polynomials
  #1
New Member
 
Join Date: Jun 2010
Posts: 25
Rep Power: 16
mystix is on a distinguished road
Hallo Foamers,

according to http://www.me.berkeley.edu/gri_mech/data/nasa_plnm.html there are 7 coefficients that define the material properties (c_p, H, S) for the temperature under 1000 K. When is the therm.dat file used?

Am I right, when I claim, that can only be a rough estimation? The jump discontinuity of material properties at the change from liquid to gas phase is not represented exactly only with these 7 coefficients.

My second question is about the ...src/thermophysicalModels/liquids/C10H22/C10H22.H file.
I think the material properties are calculated with the NSRDS-functions using the parameters in the C10H22.H file. Is this right?

c_p is now calculated two times. First in the therm.dat file and second in the liquids folder. What is used when?

Please bring some light into the dark.

Best regards
Markus
mystix is offline   Reply With Quote

Old   August 9, 2010, 08:38
Default
  #2
Super Moderator
 
niklas's Avatar
 
Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
Posts: 693
Rep Power: 29
niklas will become famous soon enoughniklas will become famous soon enough
Quote:
Originally Posted by mystix View Post
according to http://www.me.berkeley.edu/gri_mech/data/nasa_plnm.html there are 7 coefficients that define the material properties (c_p, H, S) for the temperature under 1000 K. When is the therm.dat file used?
when you use multiple species

Quote:
Originally Posted by mystix View Post
Am I right, when I claim, that can only be a rough estimation? The jump discontinuity of material properties at the change from liquid to gas phase is not represented exactly only with these 7 coefficients.
yes, therm.dat only applies for gaseous properties, but what jump discontinuties are you referring to? The enthalpy of the liquid is calculated (in dieselSpray) using the therm.dat gas-enthalpy and the liquid NSRDS latent heat function to avoid inconsistensies. There are some gas-properties available in the liquids as well, but I dont think they are used anywhere at the moment.
They have only been included because the data is there, so why not include it in case it
might be needed in the future.

Quote:
Originally Posted by mystix View Post
My second question is about the ...src/thermophysicalModels/liquids/C10H22/C10H22.H file.
I think the material properties are calculated with the NSRDS-functions using the parameters in the C10H22.H file. Is this right?
yes, but only for the liquid properties.

Quote:
Originally Posted by mystix View Post
c_p is now calculated two times. First in the therm.dat file and second in the liquids folder. What is used when?
c_p for the liquid properties are calculated using the NSRDS-functions, ie the liquids/C10H12.H file,
whereas the c_p for the gas is calculated using the therm.dat file.
niklas is offline   Reply With Quote

Old   August 9, 2010, 11:25
Question
  #3
New Member
 
Join Date: Jun 2010
Posts: 25
Rep Power: 16
mystix is on a distinguished road
Thank you for answer

You are right, there is no jump discontinuity when the gas phase and the liquid phase properties are determined in the therm.dat respectively in the liquid-folder.

I am just confused by
Quote:
when you use multiple species
When I have a single component fuel the therm.dat is not used?

How is therm.dat file used when I have a 3 component fuel (35% C6H14, 40% C7H16, 25% C10H22)?

A parcel represents droplets with the same properties like velocity and temperature. When I have a 3 component mixture a parcel represents the well mixed mixture of these 3 components. The concentrations of the species change not spatial in one parcel but over time, due to different material properties. All conservation equations are calculated for every component.
The liquid evaporates and changes to the gas phase. Is now the therm.dat file used or when does the therm.dat takes influence?
mystix is offline   Reply With Quote

Old   August 9, 2010, 14:55
Default
  #4
Super Moderator
 
niklas's Avatar
 
Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
Posts: 693
Rep Power: 29
niklas will become famous soon enoughniklas will become famous soon enough
Quote:
Originally Posted by mystix View Post
When I have a single component fuel the therm.dat is not used?
yes it is.You say you have 1 species, but that's just the fuel, what about the other species, like N2, O2 etc.

Quote:
Originally Posted by mystix View Post
How is therm.dat file used when I have a 3 component fuel (35% C6H14, 40% C7H16, 25% C10H22)?
The same as if you would have only 1 species, or a billion.

Quote:
Originally Posted by mystix View Post
A parcel represents droplets with the same properties like velocity and temperature. When I have a 3 component mixture a parcel represents the well mixed mixture of these 3 components. The concentrations of the species change not spatial in one parcel but over time, due to different material properties. All conservation equations are calculated for every component.
The liquid evaporates and changes to the gas phase. Is now the therm.dat file used or when does the therm.dat takes influence?
therm.dat is used whenever you related the enthalpy, temperature and specie concentrations in the gas phase.
I can't write it much clearer than that.
niklas is offline   Reply With Quote

Old   August 20, 2010, 08:21
Question
  #5
New Member
 
Join Date: Jun 2010
Posts: 25
Rep Power: 16
mystix is on a distinguished road
Quote:
There are some gas-properties available in the liquids as well, but I dont think they are used anywhere at the moment.
How do you know? The vapour thermal conductivity is only calculated with the NSDRS functions, not in the therm.dat. The vapour diffusivity is only calculated with the API function and not in the therm.dat.

In the therm.dat there are only the gas properties of the thermal conductivity c_p, enthalpy H and entropy S calculated.
This cant be enough :/
mystix is offline   Reply With Quote

Old   May 31, 2018, 04:17
Default
  #6
New Member
 
Shailja
Join Date: Nov 2017
Posts: 16
Rep Power: 9
Shailja is on a distinguished road
Hii

I am currently working on diselFoam and I was wondering what numbers are given in the liquidProperties section of the C7H16.C, as for others parameter like Cp,Rho etc they seem some numerical coefficients to describe them in terms of temperature as given in link http://combustion.berkeley.edu/gri-m...nasa_plnm.html.
but what quantities are given under liquidProperties section? Can anybody Help please?

regards
Shailja
Shailja is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
NASA Format Stone CFX 3 August 11, 2021 03:16
NASA FORMAT - AIR cynthia CFX 6 November 15, 2011 08:20
NASA rotor 67 2D Parametric Model t_shirt Main CFD Forum 1 May 16, 2010 16:29
NASA polynomials, thermo.dat tables Tomislav Sencic Main CFD Forum 8 December 15, 2009 11:09
How to Read Nasa Format Stone CFX 6 March 20, 2006 03:03


All times are GMT -4. The time now is 09:37.